xenocara/doc/xorg-docs/specs/X11/CH06

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.sp 1
.ce 3
\s+1\fBChapter 6\fP\s-1

\s+1\fBColor Management Functions\fP\s-1
.sp 2
.nr H1 6
.nr H2 0
.nr H3 0
.nr H4 0
.nr H5 0
.na
.LP
.XS
Chapter 6: Color Management Functions 
.XE
Each X window always has an associated colormap that
provides a level of indirection between pixel values and colors displayed
on the screen.
Xlib provides functions that you can use to manipulate a colormap.
The X protocol defines colors using values in the RGB color space.
The RGB color space is device dependent;
rendering an RGB value on differing output devices typically results
in different colors.
Xlib also provides a means for clients to specify color using
device-independent color spaces for consistent results across devices.
Xlib supports device-independent color spaces derivable from the CIE XYZ
color space.
This includes the CIE XYZ, xyY, L*u*v*, and L*a*b* color spaces as well as
the TekHVC color space.
.LP
This chapter discusses how to:
.IP \(bu 5
Create, copy, and destroy a colormap
.IP \(bu 5
Specify colors by name or value
.IP \(bu 5
Allocate, modify, and free color cells
.IP \(bu 5
Read entries in a colormap
.IP \(bu 5
Convert between color spaces
.IP \(bu 5
Control aspects of color conversion
.IP \(bu 5
Query the color gamut of a screen
.IP \(bu 5
Add new color spaces
.LP
All functions, types, and symbols in this chapter with the prefix ``Xcms''
are defined in
.hN X11/Xcms.h .
The remaining functions and types are defined in
.hN X11/Xlib.h .
.LP
Functions in this chapter manipulate the representation of color on the
screen.
For each possible value that a pixel can take in a window,
there is a color cell in the colormap.
For example, 
if a window is 4 bits deep, pixel values 0 through 15 are defined. 
A colormap is a collection of color cells.
A color cell consists of a triple of red, green, and blue (RGB) values.
The hardware imposes limits on the number of significant
bits in these values.
As each pixel is read out of display memory, the pixel
is looked up in a colormap.
The RGB value of the cell determines what color is displayed on the screen.
On a grayscale display with a black-and-white monitor, 
the values are combined to determine the brightness on the screen.
.LP
Typically, an application allocates color cells or sets of color cells
to obtain the desired colors.
The client can allocate read-only cells.
In which case, 
the pixel values for these colors can be shared among multiple applications, 
and the RGB value of the cell cannot be changed.
If the client allocates read/write cells,
they are exclusively owned by the client,
and the color associated with the pixel value can be changed at will.
Cells must be allocated (and, if read/write, initialized with an RGB value)
by a client to obtain desired colors.
The use of pixel value for an
unallocated cell results in an undefined color.
.LP
Because colormaps are associated with windows, X supports displays
with multiple colormaps and, indeed, different types of colormaps.
If there are insufficient colormap resources in the display,
some windows will display in their true colors, and others
will display with incorrect colors.
A window manager usually controls which windows are displayed
in their true colors if more than one colormap is required for
the color resources the applications are using.
At any time, there is a set of installed colormaps for a screen.
Windows using one of the installed colormaps display with true colors, and
windows using other colormaps generally display with incorrect colors.
You can control the set of installed colormaps by using
.PN XInstallColormap
and
.PN XUninstallColormap .
.LP
Colormaps are local to a particular screen.
Screens always have a default colormap,
and programs typically allocate cells out of this colormap.
Generally, you should not write applications that monopolize 
color resources.
Although some hardware supports multiple colormaps installed at one time,
many of the hardware displays
built today support only a single installed colormap, so the primitives
are written to encourage sharing of colormap entries between applications.
.LP
The 
.PN DefaultColormap 
macro returns the default colormap.
The 
.PN DefaultVisual 
macro
returns the default visual type for the specified screen.
.IN "Color map"
Possible visual types are 
.PN StaticGray , 
.PN GrayScale , 
.PN StaticColor ,
.PN PseudoColor , 
.PN TrueColor , 
or 
.PN DirectColor 
(see section 3.1).
.NH 2
Color Structures
.XS
\*(SN Color Structures
.XE
.LP
Functions that operate only on RGB color space values use an
.PN XColor
structure, which contains:
.LP
.IN "XColor" "" "@DEF@"
.sM
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	unsigned long pixel;	/* pixel value */
	unsigned short red, green, blue;	/* rgb values */
	char flags;	/* DoRed, DoGreen, DoBlue */	
	char pad;
} XColor;
.De
.LP
.eM
The red, green, and blue values are always in the range 0 to 65535
inclusive, independent of the number of bits actually used in the
display hardware.
The server scales these values down to the range used by the hardware.
Black is represented by (0,0,0), 
and white is represented by (65535,65535,65535).
.IN "Color"
In some functions,
the flags member controls which of the red, green, and blue members is used 
and can be the inclusive OR of zero or more of
.PN DoRed ,
.PN DoGreen ,
and 
.PN DoBlue .
.LP
.sp
Functions that operate on all color space values use an
.PN XcmsColor
structure.
This structure contains a union of substructures,
each supporting color specification encoding for a particular color space.
Like the
.PN XColor
structure, the
.PN XcmsColor
structure contains pixel
and color specification information (the spec member in the 
.PN XcmsColor
structure).
.IN "XcmsColor" "" "@DEF@"
.sM
.LP
.Ds 0
.TA .5i 1i 2.5i
.ta .5i 1i 2.5i
typedef unsigned long XcmsColorFormat;			/* Color Specification Format */

typedef struct {
	union {
		XcmsRGB RGB;
		XcmsRGBi RGBi;
		XcmsCIEXYZ CIEXYZ;
		XcmsCIEuvY CIEuvY;
		XcmsCIExyY CIExyY;
		XcmsCIELab CIELab;
		XcmsCIELuv CIELuv;
		XcmsTekHVC TekHVC;
		XcmsPad Pad;
	} spec;
	unsigned long pixel;
	XcmsColorFormat format;
} XcmsColor;			/* Xcms Color Structure */
.De
.LP
.eM
Because the color specification can be encoded for the various color spaces, 
encoding for the spec member is identified by the format member,
which is of type
.PN XcmsColorFormat .
The following macros define standard formats.
.sM
.TS
lw(.5i) lw(1.6i) lw(1.4i) lw(1.5i).
T{
#define
T}	T{
.PN XcmsUndefinedFormat
T}	T{
0x00000000
T}
T{
#define
T}	T{
.PN XcmsCIEXYZFormat
T}	T{
0x00000001
T}	T{
/* CIE XYZ */
T}
T{
#define
T}	T{
.PN XcmsCIEuvYFormat
T}	T{
0x00000002
T}	T{
/* CIE u'v'Y */
T}
T{
#define
T}	T{
.PN XcmsCIExyYFormat
T}	T{
0x00000003
T}	T{
/* CIE xyY */
T}
T{
#define
T}	T{
.PN XcmsCIELabFormat
T}	T{
0x00000004
T}	T{
/* CIE L*a*b* */
T}
T{
#define
T}	T{
.PN XcmsCIELuvFormat
T}	T{
0x00000005
T}	T{
/* CIE L*u*v* */
T}
T{
#define
T}	T{
.PN XcmsTekHVCFormat
T}	T{
0x00000006
T}	T{
/* TekHVC */
T}
T{
#define
T}	T{
.PN XcmsRGBFormat
T}	T{
0x80000000
T}	T{
/* RGB Device */
T}
T{
#define
T}	T{
.PN XcmsRGBiFormat
T}	T{
0x80000001
T}	T{
/* RGB Intensity */
T}
.TE
.LP
.eM
Formats for device-independent color spaces are
distinguishable from those for device-dependent spaces by the 32nd bit.
If this bit is set,
it indicates that the color specification is in a device-dependent form;
otherwise, it is in a device-independent form.
If the 31st bit is set,
this indicates that the color space has been added to Xlib at run time
(see section 6.12.4).
The format value for a color space added at run time may be different each
time the program is executed.
If references to such a color space must be made outside the client
(for example, storing a color specification in a file),
then reference should be made by color space string prefix
(see 
.PN XcmsFormatOfPrefix
and
.PN XcmsPrefixOfFormat ).
.LP
Data types that describe the color specification encoding for the various
color spaces are defined as follows:
.sM
.IN "XcmsRGB" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef double XcmsFloat;

typedef struct {
	unsigned short red;	/* 0x0000 to 0xffff */
	unsigned short green;	/* 0x0000 to 0xffff */
	unsigned short blue;	/* 0x0000 to 0xffff */
} XcmsRGB;		/* RGB Device */
.De
.IN "XcmsRGBi" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	XcmsFloat red;	/* 0.0 to 1.0 */
	XcmsFloat green;	/* 0.0 to 1.0 */
	XcmsFloat blue;	/* 0.0 to 1.0 */
} XcmsRGBi;		/* RGB Intensity */
.De
.IN "XcmsCIEXYZ" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	XcmsFloat X;
	XcmsFloat Y;	/* 0.0 to 1.0 */
	XcmsFloat Z;
} XcmsCIEXYZ;		/* CIE XYZ */
.De
.IN "XcmsCIEuvY" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	XcmsFloat u_prime;	/* 0.0 to ~0.6 */
	XcmsFloat v_prime;	/* 0.0 to ~0.6 */
	XcmsFloat Y; 	/* 0.0 to 1.0 */
} XcmsCIEuvY;		/* CIE u'v'Y */
.De
.IN "XcmsCIExyY" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	XcmsFloat x; 	/* 0.0 to ~.75 */
	XcmsFloat y; 	/* 0.0 to ~.85 */
	XcmsFloat Y; 	/* 0.0 to 1.0 */
} XcmsCIExyY;		/* CIE xyY */
.De
.IN "XcmsCIELab" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	XcmsFloat L_star; 	/* 0.0 to 100.0 */
	XcmsFloat a_star;
	XcmsFloat b_star;
} XcmsCIELab;		/* CIE L*a*b* */
.De
.IN "XcmsCIELuv" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	XcmsFloat L_star; 	/* 0.0 to 100.0 */
	XcmsFloat u_star;
	XcmsFloat v_star;
} XcmsCIELuv;		/* CIE L*u*v* */
.De
.IN "XcmsTekHVC" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	XcmsFloat H; 	/* 0.0 to 360.0 */
	XcmsFloat V; 	/* 0.0 to 100.0 */
	XcmsFloat C; 	/* 0.0 to 100.0 */
} XcmsTekHVC;		/* TekHVC */
.De
.IN "XcmsPad" "" "@DEF@"
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct {
	XcmsFloat pad0;
	XcmsFloat pad1;
	XcmsFloat pad2;
	XcmsFloat pad3;
} XcmsPad;		/* four doubles */
.De
.LP
.eM
The device-dependent formats provided allow color specification in:
.IP \(bu 5
RGB Intensity
.Pn ( XcmsRGBi )
.IP
Red, green, and blue linear intensity values,
floating-point values from 0.0 to 1.0,
where 1.0 indicates full intensity, 0.5 half intensity, and so on.
.IP \(bu 5
RGB Device
.Pn ( XcmsRGB )
.IP
Red, green, and blue values appropriate for the specified output device.
.PN XcmsRGB
values are of type unsigned short,
scaled from 0 to 65535 inclusive,
and are interchangeable with the red, green, and blue values in an 
.PN XColor
structure. 
.LP
It is important to note that RGB Intensity values are not gamma corrected
values.
In contrast,
RGB Device values generated as a result of converting color specifications 
are always gamma corrected, and
RGB Device values acquired as a result of querying a colormap
or passed in by the client are assumed by Xlib to be gamma corrected.
The term \fIRGB value\fP in this manual always refers to an RGB Device value.
.NH 2
Color Strings
.XS
\*(SN Color Strings
.XE
.LP
Xlib provides a mechanism for using string names for colors.
A color string may either contain an abstract color name
or a numerical color specification.
Color strings are case-insensitive.
.LP
Color strings are used in the following functions:
.IP \(bu 5
.PN XAllocNamedColor
.IP \(bu 5
.PN XcmsAllocNamedColor
.IP \(bu 5
.PN XLookupColor
.IP \(bu 5
.PN XcmsLookupColor
.IP \(bu 5
.PN XParseColor
.IP \(bu 5
.PN XStoreNamedColor
.LP
Xlib supports the use of abstract color names, for example, red or blue.
A value for this abstract name is obtained by searching one or more color
name databases.
Xlib first searches zero or more client-side databases;
the number, location, and content of these databases is
implementation-dependent and might depend on the current locale.
If the name is not found, Xlib then looks for the color in the
X server's database.
If the color name is not in the Host Portable Character Encoding,
the result is implementation-dependent.
.LP
A numerical color specification
consists of a color space name and a set of values in the following syntax:
.LP
.sM
.Ds 0
\fI<color_space_name>\fP:\fI<value>/.../<value>\fP
.De
.LP
.eM
The following are examples of valid color strings.
.LP
.Ds 0
"CIEXYZ:0.3227/0.28133/0.2493"
"RGBi:1.0/0.0/0.0"
"rgb:00/ff/00"
"CIELuv:50.0/0.0/0.0"
.De
The syntax and semantics of numerical specifications are given
for each standard color space in the following sections.
.NH 3
RGB Device String Specification
.XS
\*(SN RGB Device String Specification
.XE
.LP
An RGB Device specification is identified by
the prefix ``rgb:'' and conforms to the following syntax:
.LP
.\" Start marker code here
.Ds 0
rgb:\fI<red>/<green>/<blue>\fP

    \fI<red>\fP, \fI<green>\fP, \fI<blue>\fP := \fIh\fP | \fIhh\fP | \fIhhh\fP | \fIhhhh\fP
    \fIh\fP := single hexadecimal digits (case insignificant)
.De
.\" End marker code here
.LP
Note that \fIh\fP indicates the value scaled in 4 bits, 
\fIhh\fP the value scaled in 8 bits,
\fIhhh\fP the value scaled in 12 bits,
and \fIhhhh\fP the value scaled in 16 bits, respectively.
.LP
Typical examples are the strings ``rgb:ea/75/52'' and ``rgb:ccc/320/320'',
but mixed numbers of hexadecimal digit strings 
(``rgb:ff/a5/0'' and ``rgb:ccc/32/0'')
are also allowed.
.LP
For backward compatibility, an older syntax for RGB Device is
supported, but its continued use is not encouraged.
The syntax is an initial sharp sign character followed by
a numeric specification, in one of the following formats:
.LP
.\" Start marker code here
.Ds 0
.TA 2i
.ta 2i
#RGB	(4 bits each)
#RRGGBB	(8 bits each)
#RRRGGGBBB	(12 bits each)
#RRRRGGGGBBBB	(16 bits each)
.De
.\" End marker code here
.LP
The R, G, and B represent single hexadecimal digits.
When fewer than 16 bits each are specified, 
they represent the most significant bits of the value
(unlike the ``rgb:'' syntax, in which values are scaled).
For example, the string ``#3a7'' is the same as ``#3000a0007000''.
.NH 3
RGB Intensity String Specification
.XS
\*(SN RGB Intensity String Specification
.XE
.LP
An RGB intensity specification is identified
by the prefix ``rgbi:'' and conforms to the following syntax:
.LP
.\" Start marker code here
.Ds 0
rgbi:\fI<red>/<green>/<blue>\fP
.De
.\" End marker code here
.LP
Note that red, green, and blue are floating-point values
between 0.0 and 1.0, inclusive.
The input format for these values is an optional sign,
a string of numbers possibly containing a decimal point,
and an optional exponent field containing an E or e 
followed by a possibly signed integer string.
.NH 3
Device-Independent String Specifications
.XS
\*(SN Device-Independent String Specifications
.XE
.LP
The standard device-independent string specifications have
the following syntax:
.LP
.\" Start marker code here
.Ds 0
CIEXYZ:\fI<X>/<Y>/<Z>\fP
CIEuvY:\fI<u>/<v>/<Y>\fP
CIExyY:\fI<x>/<y>/<Y>\fP
CIELab:\fI<L>/<a>/<b>\fP
CIELuv:\fI<L>/<u>/<v>\fP
TekHVC:\fI<H>/<V>/<C>\fP
.De
.\" End marker code here
.LP
All of the values (C, H, V, X, Y, Z, a, b, u, v, y, x) are
floating-point values.
The syntax for these values is an optional plus or minus sign,
a string of digits possibly containing a decimal point,
and an optional exponent field consisting of an ``E'' or ``e''
followed by an optional plus or minus followed by a string of digits.
.NH 2
Color Conversion Contexts and Gamut Mapping
.XS
\*(SN Color Conversion Contexts and Gamut Mapping
.XE
.LP
When Xlib converts device-independent color specifications
into device-dependent specifications and vice versa,
it uses knowledge about the color limitations of the screen hardware.
This information, typically called the device profile,
.IN "Device profile"
is available in a Color Conversion Context (CCC).
.IN "Color Conversion Context"
.IN "CCC"
.LP
Because a specified color may be outside the color gamut of the target screen
and the white point associated with the color specification may differ
from the white point inherent to the screen,
Xlib applies gamut mapping when it encounters certain conditions:
.IN "White point"
.IP \(bu 5
Gamut compression occurs when conversion of device-independent
color specifications to device-dependent color specifications
results in a color out of the target screen's gamut.
.IP \(bu 5
White adjustment occurs when the inherent white point of the screen
differs from the white point assumed by the client.
.LP
Gamut handling methods are stored as callbacks in the CCC,
which in turn are used by the color space conversion routines.
Client data is also stored in the CCC for each callback.
The CCC also contains the white point the client assumes to be
associated with color specifications (that is, the Client White Point).
.IN "Client White Point"
.IN "Gamut compression"
.IN "Gamut handling"
.IN "White point adjustment"
The client can specify the gamut handling callbacks and client data
as well as the Client White Point.
Xlib does not preclude the X client from performing other
forms of gamut handling (for example, gamut expansion); 
however, Xlib does not provide direct support for gamut handling
other than white adjustment and gamut compression.
.LP
Associated with each colormap is an initial CCC transparently generated by
Xlib.
.IN "Color Conversion Context" "creation"
Therefore,
when you specify a colormap as an argument to an Xlib function,
you are indirectly specifying a CCC.
.IN "CCC" "of colormap"
.IN "Color Conversion Context" "of colormap"
There is a default CCC associated with each screen.
Newly created CCCs inherit attributes from the default CCC,
so the default CCC attributes can be modified to affect new CCCs.
.IN "CCC" "default"
.IN "Color Conversion Context" "default"
.LP
Xcms functions in which gamut mapping can occur return
.PN Status 
and have specific status values defined for them, 
as follows:
.IP \(bu 5
.PN XcmsFailure
indicates that the function failed.
.IP \(bu 5
.PN XcmsSuccess
indicates that the function succeeded.
In addition,
if the function performed any color conversion,
the colors did not need to be compressed.
.IP \(bu 5
.PN XcmsSuccessWithCompression
indicates the function performed color conversion
and at least one of the colors needed to be compressed.
The gamut compression method is determined by the gamut compression
procedure in the CCC that is specified directly as a function argument
or in the CCC indirectly specified by means of the colormap argument.
.NH 2
Creating, Copying, and Destroying Colormaps
.XS
\*(SN Creating, Copying, and Destroying Colormaps
.XE
.LP
To create a colormap for a screen, use
.PN XCreateColormap .
.IN "XCreateColormap" "" "@DEF@"
.sM
.FD 0
Colormap XCreateColormap\^(\^\fIdisplay\fP, \fIw\fP\^, \fIvisual\fP\^, \fIalloc\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Window \fIw\fP\^;
.br
      Visual *\fIvisual\fP\^;
.br
      int \fIalloc\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.ds Wi on whose screen you want to create a colormap
.IP \fIw\fP 1i
Specifies the window \*(Wi.
.IP \fIvisual\fP 1i
Specifies a visual type supported on the screen.
If the visual type is not one supported by the screen, 
a
.PN BadMatch
error results.
.IP \fIalloc\fP 1i
Specifies the colormap entries to be allocated.
You can pass 
.PN AllocNone 
or 
.PN AllocAll .
.LP
.eM
The
.PN XCreateColormap
function creates a colormap of the specified visual type for the screen 
on which the specified window resides and returns the colormap ID 
associated with it.
Note that the specified window is only used to determine the screen.
.LP
The initial values of the colormap entries are undefined for the 
visual classes
.PN GrayScale ,
.PN PseudoColor ,
and
.PN DirectColor .
For
.PN StaticGray ,
.PN StaticColor ,
and
.PN TrueColor ,
the entries have defined values,
but those values are specific to the visual and are not defined by X.
For
.PN StaticGray ,
.PN StaticColor ,
and
.PN TrueColor ,
alloc must be
.PN AllocNone ,
or a
.PN BadMatch
error results.
For the other visual classes,
if alloc is
.PN AllocNone ,
the colormap initially has no allocated entries,
and clients can allocate them.
For information about the visual types,
see section 3.1.
.LP
If alloc is
.PN AllocAll ,
the entire colormap is allocated writable.
The initial values of all allocated entries are undefined.
For
.PN GrayScale
and
.PN PseudoColor ,
the effect is as if an
.PN XAllocColorCells
call returned all pixel values from zero to N \- 1,
where N is the colormap entries value in the specified visual.
For
.PN DirectColor ,
the effect is as if an
.PN XAllocColorPlanes
call returned a pixel value of zero and red_mask, green_mask, 
and blue_mask values containing the same bits as the corresponding
masks in the specified visual.
However, in all cases,
none of these entries can be freed by using
.PN XFreeColors .
.LP
.PN XCreateColormap
can generate
.PN BadAlloc ,
.PN BadMatch ,
.PN BadValue ,
and
.PN BadWindow 
errors.
.LP
.sp
To create a new colormap when the allocation out of a previously
shared colormap has failed because of resource exhaustion, use
.PN XCopyColormapAndFree .
.IN "XCopyColormapAndFree" "" "@DEF@"
.sM
.FD 0
Colormap XCopyColormapAndFree\^(\^\fIdisplay\fP, \fIcolormap\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.LP
.eM
The
.PN XCopyColormapAndFree
function creates a colormap of the same visual type and for the same screen
as the specified colormap and returns the new colormap ID.
It also moves all of the client's existing allocation from the specified
colormap to the new colormap with their color values intact 
and their read-only or writable characteristics intact and frees those entries 
in the specified colormap.
Color values in other entries in the new colormap are undefined.
If the specified colormap was created by the client with alloc set to
.PN AllocAll ,
the new colormap is also created with 
.PN AllocAll ,
all color values for all entries are copied from the specified colormap,
and then all entries in the specified colormap are freed.
If the specified colormap was not created by the client with
.PN AllocAll ,
the allocations to be moved are all those pixels and planes
that have been allocated by the client using
.PN XAllocColor ,
.PN XAllocNamedColor ,
.PN XAllocColorCells ,
or
.PN XAllocColorPlanes
and that have not been freed since they were allocated.
.LP
.PN XCopyColormapAndFree
can generate
.PN BadAlloc
and
.PN BadColor 
errors.
.LP
.sp
To destroy a colormap, use 
.PN XFreeColormap .
.IN "XFreeColormap" "" "@DEF@"
.sM
.FD 0
XFreeColormap\^(\^\fIdisplay\fP, \fIcolormap\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.ds Cm that you want to destroy
.IP \fIcolormap\fP 1i
Specifies the colormap \*(Cm.
.LP
.eM
The
.PN XFreeColormap
function deletes the association between the colormap resource ID 
and the colormap and frees the colormap storage.
However, this function has no effect on the default colormap for a screen.
If the specified colormap is an installed map for a screen,
it is uninstalled (see
.PN XUninstallColormap ).
If the specified colormap is defined as the colormap for a window (by
.PN XCreateWindow ,
.PN XSetWindowColormap ,
or
.PN XChangeWindowAttributes ),
.PN XFreeColormap
changes the colormap associated with the window to
.PN None 
and generates a
.PN ColormapNotify
event.
X does not define the colors displayed for a window with a colormap of
.PN None .
.LP
.PN XFreeColormap
can generate a
.PN BadColor 
error.
.NH 2
Mapping Color Names to Values
.XS
\*(SN Mapping Color Names to Values
.XE
.LP
.sp
To map a color name to an RGB value, use
.PN XLookupColor .
.IN "Color" "naming"
.IN "XLookupColor" "" "@DEF@"
.sM
.FD 0
Status XLookupColor\^(\^\fIdisplay\fP, \fIcolormap\fP, \fIcolor_name\fP, \
\fIexact_def_return\fP\^, \fIscreen_def_return\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      char *\fIcolor_name\fP\^;
.br
      XColor *\fIexact_def_return\fP\^, *\fIscreen_def_return\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolor_name\fP 1i
Specifies the color name string (for example, red) whose color 
definition structure you want returned.
.IP \fIexact_def_return\fP 1i
Returns the exact RGB values.
.IP \fIscreen_def_return\fP 1i
Returns the closest RGB values provided by the hardware.
.LP
.eM
The
.PN XLookupColor
function looks up the string name of a color with respect to the screen
associated with the specified colormap.
It returns both the exact color values and
the closest values provided by the screen 
with respect to the visual type of the specified colormap.
If the color name is not in the Host Portable Character Encoding, 
the result is implementation-dependent.
Use of uppercase or lowercase does not matter.
.PN XLookupColor
returns nonzero if the name is resolved;
otherwise, it returns zero.
.LP
.PN XLookupColor
can generate a
.PN BadColor 
error.
.LP
.sp
To map a color name to the exact RGB value, use
.PN XParseColor .
.IN "Color" "naming"
.IN "XParseColor" "" "@DEF@"
.sM
.FD 0
Status XParseColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \^\fIspec\fP\^, \fIexact_def_return\fP\^)
.br
        Display *\fIdisplay\fP\^;
.br
        Colormap \fIcolormap\fP\^;
.br
        char *\fIspec\fP\^;
.br
        XColor *\fIexact_def_return\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIspec\fP 1i
Specifies the color name string;
case is ignored.
.IP \fIexact_def_return\fP 1i
Returns the exact color value for later use and sets the
.PN DoRed ,
.PN DoGreen ,
and
.PN DoBlue
flags.
.LP
.eM 
The
.PN XParseColor
function looks up the string name of a color with respect to the screen
associated with the specified colormap.
It returns the exact color value.
If the color name is not in the Host Portable Character Encoding, 
the result is implementation-dependent.
Use of uppercase or lowercase does not matter.
.PN XParseColor
returns nonzero if the name is resolved;
otherwise, it returns zero.
.LP
.PN XParseColor
can generate a
.PN BadColor 
error.
.LP
.sp
To map a color name to a value in an arbitrary color space, use
.PN XcmsLookupColor .
.IN "Color" "naming"
.IN "XcmsLookupColor" "" "@DEF@"
.sM
.FD 0
Status XcmsLookupColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcolor_string\fP\^, \fIcolor_exact_return\fP\^, \fIcolor_screen_return\fP\^,
.br
			 \fIresult_format\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      char *\fIcolor_string\fP\^;
.br
      XcmsColor *\fIcolor_exact_return\fP\^, *\fIcolor_screen_return\fP\^;
.br
      XcmsColorFormat \fIresult_format\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.ds St
.IP \fIcolor_string\fP 1i
Specifies the color string\*(St.
.IP \fIcolor_exact_return\fP 1i
Returns the color specification parsed from the color string
or parsed from the corresponding string found in a color-name database.
.IP \fIcolor_screen_return\fP 1i
Returns the color that can be reproduced on the screen.
.IP \fIresult_format\fP 1i
Specifies the color format for the returned color
specifications (color_screen_return and color_exact_return arguments).
If the format is
.PN XcmsUndefinedFormat
and the color string contains a
numerical color specification,
the specification is returned in the format used in that numerical
color specification.
If the format is
.PN XcmsUndefinedFormat
and the color string contains a color name,
the specification is returned in the format used 
to store the color in the database.
.LP
.eM
The
.PN XcmsLookupColor
function looks up the string name of a color with respect to the screen
associated with the specified colormap.
It returns both the exact color values and
the closest values provided by the screen 
with respect to the visual type of the specified colormap.
The values are returned in the format specified by result_format.
If the color name is not in the Host Portable Character Encoding, 
the result is implementation-dependent.
Use of uppercase or lowercase does not matter.
.PN XcmsLookupColor
returns
.PN XcmsSuccess
or
.PN XcmsSuccessWithCompression
if the name is resolved; otherwise, it returns
.PN XcmsFailure .
If
.PN XcmsSuccessWithCompression
is returned, the color specification returned in 
color_screen_return is the result of gamut compression.
.NH 2
Allocating and Freeing Color Cells
.XS
\*(SN Allocating and Freeing Color Cells
.XE
.LP
There are two ways of allocating color cells: 
explicitly as read-only entries, one pixel value at a time,
or read/write,
where you can allocate a number of color cells and planes simultaneously.
.IN "Read-only colormap cells"
A read-only cell has its RGB value set by the server.
.IN "Read/write colormap cells"
Read/write cells do not have defined colors initially;
functions described in the next section must be used to store values into them.
Although it is possible for any client to store values into a read/write
cell allocated by another client,
read/write cells normally should be considered private to the client
that allocated them.
.LP
Read-only colormap cells are shared among clients.
The server counts each allocation and freeing of the cell by clients.
When the last client frees a shared cell, the cell is finally deallocated.
If a single client allocates the same read-only cell multiple
times, the server counts each such allocation, not just the first one.
.LP
.sp
To allocate a read-only color cell with an RGB value, use
.PN XAllocColor .
.IN "Allocation" "read-only colormap cells"
.IN "Read-only colormap cells" "allocating"
.IN "Color" "allocation"
.IN "XAllocColor" "" "@DEF@"
.sM
.FD 0
Status XAllocColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIscreen_in_out\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XColor *\fIscreen_in_out\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIscreen_in_out\fP 1i
Specifies and returns the values actually used in the colormap.
.LP
.eM
The
.PN XAllocColor
function allocates a read-only colormap entry corresponding to the closest
RGB value supported by the hardware.
.PN XAllocColor
returns the pixel value of the color closest to the specified
RGB elements supported by the hardware
and returns the RGB value actually used.
The corresponding colormap cell is read-only.
In addition,
.PN XAllocColor
returns nonzero if it succeeded or zero if it failed.
.IN "Color map"
.IN "Color" "allocation"
.IN "Allocation" "colormap"
.IN "read-only colormap cells"
Multiple clients that request the same effective RGB value can be assigned
the same read-only entry, thus allowing entries to be shared.
When the last client deallocates a shared cell, it is deallocated.
.PN XAllocColor
does not use or affect the flags in the
.PN XColor
structure.
.LP
.PN XAllocColor
can generate a
.PN BadColor 
error.
.EQ
delim %%
.EN
.LP
.sp
To allocate a read-only color cell with a color in arbitrary format, use
.PN XcmsAllocColor .
.IN "Allocation" "read-only colormap cells"
.IN "Read-only colormap cells" "allocating"
.IN "Color" "allocation"
.IN "XcmsAllocColor" "" "@DEF@"
.sM
.FD 0
Status XcmsAllocColor\^(\^\fIdisplay\fP\^, \fIcolormap\fP\^, \fIcolor_in_out\fP\^, \fIresult_format\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XcmsColor *\fIcolor_in_out\fP\^;
.br
      XcmsColorFormat \fIresult_format\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolor_in_out\fP 1i
Specifies the color to allocate and returns the pixel and color 
that is actually used in the colormap.
.IP \fIresult_format\fP 1i
Specifies the color format for the returned color specification.
.LP
.eM
The
.PN XcmsAllocColor
function is similar to
.PN XAllocColor
except the color can be specified in any format.
The
.PN XcmsAllocColor
function ultimately calls 
.PN XAllocColor
to allocate a read-only color cell (colormap entry) with the specified color.
.PN XcmsAllocColor
first converts the color specified
to an RGB value and then passes this to
.PN XAllocColor .
.PN XcmsAllocColor
returns the pixel value of the color cell and the color specification
actually allocated.
This returned color specification is the result of converting the RGB value
returned by 
.PN XAllocColor 
into the format specified with the result_format argument.
If there is no interest in a returned color specification, 
unnecessary computation can be bypassed if result_format is set to
.PN XcmsRGBFormat .
The corresponding colormap cell is read-only.
If this routine returns 
.PN XcmsFailure , 
the color_in_out color specification is left unchanged.
.LP
.PN XcmsAllocColor
can generate a
.PN BadColor
error.
.LP
.sp
To allocate a read-only color cell using a color name and return the closest
color supported by the hardware in RGB format, use
.PN XAllocNamedColor .
.IN "Allocation" "read-only colormap cells"
.IN "Read-only colormap cells" "allocating"
.IN "Color" "naming"
.IN "Color" "allocation"
.IN "XAllocNamedColor" "" "@DEF@"
.sM
.FD 0
Status XAllocNamedColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \
\fIcolor_name\fP\^, \fIscreen_def_return\fP\^, \fIexact_def_return\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      char *\fIcolor_name\fP\^;
.br
      XColor *\fIscreen_def_return\fP\^, *\fIexact_def_return\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolor_name\fP 1i
Specifies the color name string (for example, red) whose color 
definition structure you want returned.
.IP \fIscreen_def_return\fP 1i
Returns the closest RGB values provided by the hardware.
.IP \fIexact_def_return\fP 1i
Returns the exact RGB values.
.LP
.eM 
The
.PN XAllocNamedColor
function looks up the named color with respect to the screen that is
associated with the specified colormap.
It returns both the exact database definition and
the closest color supported by the screen.
The allocated color cell is read-only.
The pixel value is returned in screen_def_return.
If the color name is not in the Host Portable Character Encoding, 
the result is implementation-dependent.
Use of uppercase or lowercase does not matter.
If screen_def_return and exact_def_return
point to the same structure, the pixel field will be set correctly,
but the color values are undefined.
.PN XAllocNamedColor
returns nonzero if a cell is allocated;
otherwise, it returns zero.
.LP
.PN XAllocNamedColor
can generate a
.PN BadColor
error. 
.LP
.sp
To allocate a read-only color cell using a color name and return the closest
color supported by the hardware in an arbitrary format, use
.PN XcmsAllocNamedColor .
.IN "Allocation" "read-only colormap cells"
.IN "Read-only colormap cells" "allocating"
.IN "Color" "naming"
.IN "Color" "allocation"
.IN "XcmsAllocNamedColor" "" "@DEF@"
.sM
.FD 0
Status XcmsAllocNamedColor\^(\^\fIdisplay\fP\^, \fIcolormap\fP\^, \fIcolor_string\fP\^, \fIcolor_screen_return\fP\^, \fIcolor_exact_return\fP\^,
.br
                            \fIresult_format\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      char *\fIcolor_string\fP\^;
.br
      XcmsColor *\fIcolor_screen_return\fP\^;
.br
      XcmsColor *\fIcolor_exact_return\fP\^;
.br
      XcmsColorFormat \fIresult_format\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.ds St \ whose color definition structure is to be returned
.IP \fIcolor_string\fP 1i
Specifies the color string\*(St.
.IP \fIcolor_screen_return\fP 1i
Returns the pixel value of the color cell and color specification 
that actually is stored for that cell.
.IP \fIcolor_exact_return\fP 1i
Returns the color specification parsed from the color string
or parsed from the corresponding string found in a color-name database.
.IP \fIresult_format\fP 1i
Specifies the color format for the returned color
specifications (color_screen_return and color_exact_return arguments).
If the format is
.PN XcmsUndefinedFormat
and the color string contains a
numerical color specification,
the specification is returned in the format used in that numerical
color specification.
If the format is
.PN XcmsUndefinedFormat
and the color string contains a color name,
the specification is returned in the format used 
to store the color in the database.
.LP
.eM
The
.PN XcmsAllocNamedColor
function is similar to
.PN XAllocNamedColor
except that the color returned can be in any format specified.
This function
ultimately calls
.PN XAllocColor
to allocate a read-only color cell with
the color specified by a color string.
The color string is parsed into an
.PN XcmsColor
structure (see
.PN XcmsLookupColor ),
converted
to an RGB value, and finally passed to
.PN XAllocColor .
If the color name is not in the Host Portable Character Encoding, 
the result is implementation-dependent.
Use of uppercase or lowercase does not matter.
.LP
This function returns both the color specification as a result
of parsing (exact specification) and the actual color specification
stored (screen specification).
This screen specification is the result of converting the RGB value
returned by
.PN XAllocColor
into the format specified in result_format.
If there is no interest in a returned color specification,
unnecessary computation can be bypassed if result_format is set to
.PN XcmsRGBFormat .
If color_screen_return and color_exact_return
point to the same structure, the pixel field will be set correctly,
but the color values are undefined.
.LP
.PN XcmsAllocNamedColor
can generate a
.PN BadColor
error.
.LP
.sp
To allocate read/write color cell and color plane combinations for a
.PN PseudoColor
model, use
.PN XAllocColorCells .
.IN "Read/write colormap cells" "allocating"
.IN "Allocation" "read/write colormap cells"
.IN "Color" "allocation"
.IN "XAllocColorCells" "" "@DEF@"
.sM
.FD 0
Status XAllocColorCells\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcontig\fP\^, \
\fIplane_masks_return\fP\^, \fInplanes\fP\^, 
.br
                          \fIpixels_return\fP\^, \fInpixels\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      Bool \fIcontig\fP\^;
.br
      unsigned long \fIplane_masks_return\fP[\^]\^;
.br
      unsigned int \fInplanes\fP\^;
.br
      unsigned long \fIpixels_return\fP[\^]\^;
.br
      unsigned int \fInpixels\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcontig\fP 1i
Specifies a Boolean value that indicates whether the planes must be contiguous.
.IP \fIplane_mask_return\fP 1i
Returns an array of plane masks.
.\" *** JIM: NEED MORE INFO FOR THIS. ***
.IP \fInplanes\fP 1i
Specifies the number of plane masks that are to be returned in the plane masks 
array. 
.IP \fIpixels_return\fP 1i
Returns an array of pixel values. 
.IP \fInpixels\fP 1i
Specifies the number of pixel values that are to be returned in the 
pixels_return array. 
.LP
.eM
.EQ
delim %%
.EN
The
.PN XAllocColorCells
function allocates read/write color cells.
The number of colors must be positive and the number of planes nonnegative,
or a
.PN BadValue
error results.
If ncolors and nplanes are requested, 
then ncolors pixels
and nplane plane masks are returned.
No mask will have any bits set to 1 in common with
any other mask or with any of the pixels.
By ORing together each pixel with zero or more masks,
ncolors * %2 sup nplanes% distinct pixels can be produced.
All of these are
allocated writable by the request.
For 
.PN GrayScale 
or 
.PN PseudoColor , 
each mask has exactly one bit set to 1. 
For 
.PN DirectColor , 
each has exactly three bits set to 1.
If contig is 
.PN True 
and if all masks are ORed
together, a single contiguous set of bits set to 1 will be formed for 
.PN GrayScale
or 
.PN PseudoColor 
and three contiguous sets of bits set to 1 (one within each
pixel subfield) for 
.PN DirectColor .
The RGB values of the allocated
entries are undefined.
.PN XAllocColorCells
returns nonzero if it succeeded or zero if it failed.
.LP
.PN XAllocColorCells
can generate
.PN BadColor
and
.PN BadValue 
errors.
.LP
.sp
To allocate read/write color resources for a
.PN DirectColor
model, use
.PN XAllocColorPlanes .
.IN "Read/write colormap planes" "allocating"
.IN "Allocation" "read/write colormap planes"
.IN "Color" "allocation"
.IN "XAllocColorPlanes" "" "@DEF@"
.sM
.FD 0
Status XAllocColorPlanes\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcontig\fP\^, \fIpixels_return\fP\^, \fIncolors\fP\^, \fInreds\fP\^, \fIngreens\fP\^, 
.br
                           \fInblues\fP\^, \fIrmask_return\fP\^, \fIgmask_return\fP\^, \fIbmask_return\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      Bool \fIcontig\fP\^;
.br
      unsigned long \fIpixels_return\fP[\^]\^;
.br
      int \fIncolors\fP\^;
.br
      int \fInreds\fP\^, \fIngreens\fP\^, \fInblues\fP\^;
.br
      unsigned long *\fIrmask_return\fP\^, *\fIgmask_return\fP\^, *\fIbmask_return\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcontig\fP 1i
Specifies a Boolean value that indicates whether the planes must be contiguous.
.IP \fIpixels_return\fP 1i
Returns an array of pixel values. 
.PN XAllocColorPlanes
returns the pixel values in this array.
.IP \fIncolors\fP 1i
Specifies the number of pixel values that are to be returned in the 
pixels_return array. 
.IP \fInreds\fP 1i
.br
.ns
.IP \fIngreens\fP 1i
.br
.ns
.IP \fInblues\fP 1i
.br
.ns
Specify the number of red, green, and blue planes.
The value you pass must be nonnegative. 
.IP \fIrmask_return\fP 1i
.br
.ns
.IP \fIgmask_return\fP 1i
.br
.ns
.IP \fIbmask_return\fP 1i
Return bit masks for the red, green, and blue planes.
.LP
.eM
.EQ
delim %%
.EN
The specified ncolors must be positive; 
and nreds, ngreens, and nblues must be nonnegative,
or a
.PN BadValue
error results.
If ncolors colors, nreds reds, ngreens greens, and nblues blues are requested, 
ncolors pixels are returned; and the masks have nreds, ngreens, and 
nblues bits set to 1, respectively.
If contig is 
.PN True , 
each mask will have
a contiguous set of bits set to 1.
No mask will have any bits set to 1 in common with
any other mask or with any of the pixels.
For 
.PN DirectColor , 
each mask
will lie within the corresponding pixel subfield.
By ORing together
subsets of masks with each pixel value, 
ncolors * %2 sup (nreds+ngreens+nblues)% distinct pixel values can be produced. 
All of these are allocated by the request.
However, in the
colormap, there are only ncolors * %2 sup nreds% independent red entries, 
ncolors * %2 sup ngreens% independent green entries, 
and ncolors * %2 sup nblues% independent blue entries. 
This is true even for 
.PN PseudoColor .
When the colormap entry of a pixel
value is changed (using 
.PN XStoreColors ,
.PN XStoreColor ,
or 
.PN XStoreNamedColor ),
the pixel is decomposed according to the masks, 
and the corresponding independent entries are updated.
.PN XAllocColorPlanes
returns nonzero if it succeeded or zero if it failed.
.LP
.PN XAllocColorPlanes
can generate
.PN BadColor
and
.PN BadValue 
errors.
.LP
.sp
.IN "Freeing" "colors"
To free colormap cells, use
.PN XFreeColors .
.IN "XFreeColors" "" "@DEF@"
.IN "Color" "deallocation"
.sM
.FD 0
XFreeColors\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIpixels\fP\^, \fInpixels\fP\^, \fIplanes\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      unsigned long \fIpixels\fP\^[\^];
.br
      int \fInpixels\fP\^;
.br
      unsigned long \fIplanes\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.ds Pi that map to the cells in the specified colormap
.IP \fIpixels\fP 1i
Specifies an array of pixel values \*(Pi. 
.IP \fInpixels\fP 1i
Specifies the number of pixels. 
.IP \fIplanes\fP 1i
Specifies the planes you want to free.
.LP
.eM
The
.PN XFreeColors
function frees the cells represented by pixels whose values are in the
pixels array.
The planes argument should not have any bits set to 1 in common with any of the
pixels. 
The set of all pixels is produced by ORing together subsets of
the planes argument with the pixels.
The request frees all of these pixels that
were allocated by the client (using 
.IN XAllocColor
.IN XAllocNamedColor
.IN XAllocColorCells
.IN XAllocColorPlanes
.PN XAllocColor , 
.PN XAllocNamedColor ,
.PN XAllocColorCells ,
and 
.PN XAllocColorPlanes ).
Note that freeing an
individual pixel obtained from 
.PN XAllocColorPlanes 
may not actually allow
it to be reused until all of its related pixels are also freed.
Similarly,
a read-only entry is not actually freed until it has been freed by all clients,
and if a client allocates the same read-only entry multiple times,
it must free the entry that many times before the entry is actually freed.
.LP
All specified pixels that are allocated by the client in the colormap are
freed, even if one or more pixels produce an error. 
If a specified pixel is not a valid index into the colormap, a 
.PN BadValue 
error results.
If a specified pixel is not allocated by the
client (that is, is unallocated or is only allocated by another client)
or if the colormap was created with all entries writable (by passing
.PN AllocAll
to
.PN XCreateColormap ),
a
.PN BadAccess
error results. 
If more than one pixel is in error, 
the one that gets reported is arbitrary.
.LP
.PN XFreeColors
can generate
.PN BadAccess ,
.PN BadColor ,
and
.PN BadValue 
errors.
.NH 2
Modifying and Querying Colormap Cells
.XS
\*(SN Modifying and Querying Colormap Cells 
.XE
.LP
.sp
To store an RGB value in a single colormap cell, use
.PN XStoreColor .
.IN "Color" "storing"
.IN "XStoreColor" "" "@DEF@"
.sM
.FD 0
XStoreColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcolor\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XColor *\fIcolor\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolor\fP 1i
Specifies the pixel and RGB values.
.LP
.eM
The
.PN XStoreColor
function changes the colormap entry of the pixel value specified in the
pixel member of the
.PN XColor
structure.
You specified this value in the
pixel member of the
.PN XColor
structure.
This pixel value must be a read/write cell and a valid index into the colormap.
If a specified pixel is not a valid index into the colormap,
a
.PN BadValue
error results.
.PN XStoreColor
also changes the red, green, and/or blue color components.
You specify which color components are to be changed by setting
.PN DoRed ,
.PN DoGreen ,
and/or
.PN DoBlue
in the flags member of the
.PN XColor
structure.
If the colormap is an installed map for its screen, 
the changes are visible immediately.
.LP
.PN XStoreColor
can generate
.PN BadAccess ,
.PN BadColor ,
and
.PN BadValue 
errors.
.LP
.sp
To store multiple RGB values in multiple colormap cells, use
.PN XStoreColors .
.IN "Color" "storing"
.IN "XStoreColors" "" "@DEF@"
.sM
.FD 0
XStoreColors\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcolor\fP\^, \fIncolors\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XColor \fIcolor\fP\^[\^]\^;
.br
      int \fIncolors\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolor\fP 1i
Specifies an array of color definition structures to be stored.
.IP \fIncolors\fP 1i
.\"Specifies the number of color definition structures. 
Specifies the number of 
.PN XColor
structures in the color definition array.
.LP
.eM
The
.PN XStoreColors
function changes the colormap entries of the pixel values
specified in the pixel members of the
.PN XColor
structures.
You specify which color components are to be changed by setting 
.PN DoRed ,
.PN DoGreen ,
and/or
.PN DoBlue
in the flags member of the
.PN XColor
structures.
If the colormap is an installed map for its screen, the
changes are visible immediately.
.PN XStoreColors 
changes the specified pixels if they are allocated writable in the colormap 
by any client, even if one or more pixels generates an error.
If a specified pixel is not a valid index into the colormap, a
.PN BadValue
error results.
If a specified pixel either is unallocated or is allocated read-only, a
.PN BadAccess
error results.
If more than one pixel is in error, 
the one that gets reported is arbitrary.
.LP
.PN XStoreColors
can generate
.PN BadAccess ,
.PN BadColor ,
and
.PN BadValue 
errors.
.LP
.sp
To store a color of arbitrary format in a single colormap cell, use
.PN XcmsStoreColor .
.IN "Color" "storing"
.IN "XcmsStoreColor" "" "@DEF@"
.sM
.FD 0
Status XcmsStoreColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcolor\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XcmsColor *\fIcolor\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolor\fP 1i
Specifies the color cell and the color to store.
Values specified in this
.PN XcmsColor
structure remain unchanged on return.
.LP
.eM
The
.PN XcmsStoreColor
function converts the color specified in the
.PN XcmsColor
structure into RGB values.
It then uses this RGB specification in an
.PN XColor
structure, whose three flags 
.Pn ( DoRed , 
.PN DoGreen ,
and
.PN DoBlue )
are set, in a call to
.PN XStoreColor
to change the color cell specified by the pixel member of the
.PN XcmsColor
structure.
This pixel value must be a valid index for the specified colormap,
and the color cell specified by the pixel value must be a read/write cell.
If the pixel value is not a valid index, a
.PN BadValue
error results.
If the color cell is unallocated or is allocated read-only, a
.PN BadAccess
error results.
If the colormap is an installed map for its screen, 
the changes are visible immediately.
.LP
Note that 
.PN XStoreColor
has no return value; therefore, an
.PN XcmsSuccess
return value from this function indicates that the conversion 
to RGB succeeded and the call to
.PN XStoreColor
was made.
To obtain the actual color stored, use
.PN XcmsQueryColor .
Because of the screen's hardware limitations or gamut compression,
the color stored in the colormap may not be identical
to the color specified.
.LP
.PN XcmsStoreColor
can generate
.PN BadAccess ,
.PN BadColor ,
and
.PN BadValue
errors.
.LP
.sp
To store multiple colors of arbitrary format in multiple colormap cells, use
.PN XcmsStoreColors .
.IN "Color" "storing"
.IN "XcmsStoreColors" "" "@DEF@"
.sM
.FD 0
Status XcmsStoreColors\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcolors\fP\^, \fIncolors\fP\^, \fIcompression_flags_return\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XcmsColor \fIcolors\fP\^[\^]\^;
.br
      int \fIncolors\fP\^;
.br
      Bool \fIcompression_flags_return\fP\^[\^]\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolors\fP 1i
Specifies the color specification array of
.PN XcmsColor
structures, each specifying a color cell and the color to store in that
cell.
Values specified in the array remain unchanged upon return.
.IP \fIncolors\fP 1i
Specifies the number of 
.PN XcmsColor
structures in the color-specification array.
.IP \fIcompression_flags_return\fP 1i
Returns an array of Boolean values indicating compression status.
If a non-NULL pointer is supplied,
each element of the array is set to
.PN True
if the corresponding color was compressed and
.PN False
otherwise.
Pass NULL if the compression status is not useful.
.LP
.eM
The
.PN XcmsStoreColors
function converts the colors specified in the array of
.PN XcmsColor
structures into RGB values and then uses these RGB specifications in
.PN XColor
structures, whose three flags 
.Pn ( DoRed , 
.PN DoGreen ,
and
.PN DoBlue )
are set, in a call to
.PN XStoreColors
to change the color cells specified by the pixel member of the corresponding
.PN XcmsColor
structure.
Each pixel value must be a valid index for the specified colormap,
and the color cell specified by each pixel value must be a read/write cell.
If a pixel value is not a valid index, a
.PN BadValue
error results.
If a color cell is unallocated or is allocated read-only, a
.PN BadAccess
error results.
If more than one pixel is in error,
the one that gets reported is arbitrary.
If the colormap is an installed map for its screen, 
the changes are visible immediately.
.LP
Note that 
.PN XStoreColors
has no return value; therefore, an
.PN XcmsSuccess
return value from this function indicates that conversions 
to RGB succeeded and the call to
.PN XStoreColors
was made.
To obtain the actual colors stored, use
.PN XcmsQueryColors .
Because of the screen's hardware limitations or gamut compression,
the colors stored in the colormap may not be identical
to the colors specified.
.LP
.PN XcmsStoreColors
can generate
.PN BadAccess ,
.PN BadColor ,
and
.PN BadValue
errors.
.LP
.sp
To store a color specified by name in a single colormap cell, use
.PN XStoreNamedColor .
.IN "Color" "storing"
.IN "Color" "naming"
.IN "XStoreNamedColor" "" "@DEF@"
.sM
.FD 0
XStoreNamedColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcolor\fP\^, \fIpixel\fP\^, \fIflags\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      char *\^\fIcolor\fP\^;
.br
      unsigned long \fIpixel\fP\^;
.br
      int \fIflags\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolor\fP 1i
Specifies the color name string (for example, red). 
.IP \fIpixel\fP 1i
Specifies the entry in the colormap. 
.IP \fIflags\fP 1i
Specifies which red, green, and blue components are set.
.LP
.eM 
The
.PN XStoreNamedColor
function looks up the named color with respect to the screen associated with
the colormap and stores the result in the specified colormap.
The pixel argument determines the entry in the colormap.
The flags argument determines which of the red, green, and blue components 
are set. 
You can set this member to the
bitwise inclusive OR of the bits 
.PN DoRed , 
.PN DoGreen , 
and 
.PN DoBlue .
If the color name is not in the Host Portable Character Encoding, 
the result is implementation-dependent.
Use of uppercase or lowercase does not matter.
If the specified pixel is not a valid index into the colormap, a
.PN BadValue
error results.
If the specified pixel either is unallocated or is allocated read-only, a
.PN BadAccess
error results.
.LP
.PN XStoreNamedColor
can generate
.PN BadAccess ,
.PN BadColor ,
.PN BadName ,
and 
.PN BadValue 
errors.
.LP
The
.PN XQueryColor
and
.PN XQueryColors
functions take pixel values in the pixel member of
.PN XColor
structures and store in the structures the RGB values for those
pixels from the specified colormap.
The values returned for an unallocated entry are undefined.
These functions also set the flags member in the
.PN XColor
structure to all three colors.
If a pixel is not a valid index into the specified colormap, a
.PN BadValue
error results.
If more than one pixel is in error,
the one that gets reported is arbitrary.
.LP
.sp
To query the RGB value of a single colormap cell, use
.PN XQueryColor .
.IN "Color" "querying"
.IN "XQueryColor" "" "@DEF@"
.sM
.FD 0
XQueryColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIdef_in_out\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XColor *\fIdef_in_out\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIdef_in_out\fP 1i
Specifies and returns the RGB values for the pixel specified in the structure.
.LP
.eM
The
.PN XQueryColor
function returns the current RGB value for the pixel in the
.PN XColor
structure and sets the
.PN DoRed ,
.PN DoGreen ,
and
.PN DoBlue
flags.
.LP
.PN XQueryColor
can generate
.PN BadColor
and
.PN BadValue 
errors.
.LP
.sp
To query the RGB values of multiple colormap cells, use
.PN XQueryColors .
.IN "Color" "querying"
.IN "XQueryColors" "" "@DEF@"
.sM
.FD 0
XQueryColors\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIdefs_in_out\fP\^, \fIncolors\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XColor \fIdefs_in_out\fP[\^]\^;
.br
      int \fIncolors\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIdefs_in_out\fP 1i
Specifies and returns an array of color definition structures for the pixel
specified in the structure.
.IP \fIncolors\fP 1i
.\"Specifies the number of color definition structures. 
Specifies the number of 
.PN XColor
structures in the color definition array.
.LP
.eM
The
.PN XQueryColors
function returns the RGB value for each pixel in each
.PN XColor
structure and sets the
.PN DoRed ,
.PN DoGreen ,
and
.PN DoBlue
flags in each structure.

.LP
.PN XQueryColors
can generate
.PN BadColor
and
.PN BadValue 
errors.
.sp
.LP
To query the color of a single colormap cell in an arbitrary format, use
.PN XcmsQueryColor .
.IN "Color" "querying"
.IN "XcmsQueryColor" "" "@DEF@"
.sM
.FD 0
Status XcmsQueryColor\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcolor_in_out\fP\^, \fIresult_format\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XcmsColor *\fIcolor_in_out\fP\^;
.br
      XcmsColorFormat \fIresult_format\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolor_in_out\fP 1i
Specifies the pixel member that indicates the color cell to query.
The color specification stored for the color cell is returned in this
.PN XcmsColor
structure.
.IP \fIresult_format\fP 1i
Specifies the color format for the returned color specification.
.LP
.eM
The
.PN XcmsQueryColor
function obtains the RGB value
for the pixel value in the pixel member of the specified
.PN XcmsColor
structure and then
converts the value to the target format as
specified by the result_format argument.
If the pixel is not a valid index in the specified colormap, a
.PN BadValue
error results.
.LP
.PN XcmsQueryColor
can generate
.PN BadColor
and
.PN BadValue
errors.
.sp
.LP
To query the color of multiple colormap cells in an arbitrary format, use
.PN XcmsQueryColors .
.IN "Color" "querying"
.IN "XcmsQueryColors" "" "@DEF@"
.sM
.FD 0
Status XcmsQueryColors\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIcolors_in_out\fP\^, \fIncolors\fP\^, \fIresult_format\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XcmsColor \fIcolors_in_out\fP\^[\^]\^;
.br
      unsigned int \fIncolors\fP\^;
.br
      XcmsColorFormat \fIresult_format\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIcolors_in_out\fP 1i
Specifies an array of
.PN XcmsColor
structures, each pixel member indicating the color cell to query.
The color specifications for the color cells are returned in these structures.
.IP \fIncolors\fP 1i
Specifies the number of 
.PN XcmsColor
structures in the color-specification array.
.IP \fIresult_format\fP 1i
Specifies the color format for the returned color specification.
.LP
.eM
The
.PN XcmsQueryColors
function obtains the RGB values
for pixel values in the pixel members of
.PN XcmsColor
structures and then
converts the values to the target format as
specified by the result_format argument.
If a pixel is not a valid index into the specified colormap, a
.PN BadValue
error results.
If more than one pixel is in error,
the one that gets reported is arbitrary.
.LP
.PN XcmsQueryColors
can generate
.PN BadColor
and
.PN BadValue
errors.
.NH 2
Color Conversion Context Functions
.XS
\*(SN Color Conversion Context Functions
.XE
.LP
This section describes functions to create, modify,
and query Color Conversion Contexts (CCCs).
.LP
Associated with each colormap is an initial CCC transparently generated by
Xlib.
.IN "Color Conversion Context" "creation"
Therefore, when you specify a colormap as an argument to a function,
you are indirectly specifying a CCC.
.IN "CCC" "of colormap"
.IN "Color Conversion Context" "of colormap"
The CCC attributes that can be modified by the X client are:
.IP \(bu 5
Client White Point
.IP \(bu 5
Gamut compression procedure and client data
.IP \(bu 5
White point adjustment procedure and client data
.LP
The initial values for these attributes are implementation specific.
The CCC attributes for subsequently created CCCs can be defined
by changing the CCC attributes of the default CCC.
.IN "CCC" "default"
.IN "Color Conversion Context" "default"
There is a default CCC associated with each screen.
.NH 3
Getting and Setting the Color Conversion Context of a Colormap
.XS
\*(SN Getting and Setting the Color Conversion Context of a Colormap
.XE
.LP
.sp
To obtain the CCC associated with a colormap, use
.PN XcmsCCCOfColormap .
.IN "XcmsCCCOfColormap" "" "@DEF@"
.IN "Colormap" "CCC of"
.IN "CCC" "of colormap"
.IN "Color Conversion Context" "of colormap"
.sM
.FD 0
XcmsCCC XcmsCCCOfColormap\^(\^\fIdisplay\fP, \fIcolormap\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.LP
.eM
The
.PN XcmsCCCOfColormap
function returns the CCC associated with the specified colormap.
Once obtained, 
the CCC attributes can be queried or modified.
Unless the CCC associated with the specified colormap is changed with
.PN XcmsSetCCCOfColormap ,
this CCC is used when the specified colormap is used as an argument 
to color functions.
.sp
.LP
To change the CCC associated with a colormap, use
.PN XcmsSetCCCOfColormap .
.IN "XcmsSetCCCOfColormap" "" "@DEF@"
.IN "Colormap" "CCC of"
.IN "CCC" "of colormap"
.IN "Color Conversion Context" "of colormap"
.sM
.FD 0
XcmsCCC XcmsSetCCCOfColormap\^(\^\fIdisplay\fP, \fIcolormap\fP\^, \fIccc\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Colormap \fIcolormap\fP\^;
.br
      XcmsCCC \fIccc\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcolormap\fP 1i
Specifies the colormap.
.IP \fIccc\fP 1i
Specifies the CCC.
.LP
.eM
The
.PN XcmsSetCCCOfColormap
function changes the CCC associated with the specified colormap.
It returns the CCC previously associated with the colormap.
If they are not used again in the application,
CCCs should be freed by calling
.PN XcmsFreeCCC .
Several colormaps may share the same CCC without restriction; this
includes the CCCs generated by Xlib with each colormap.  Xlib, however,
creates a new CCC with each new colormap.
.NH 3
Obtaining the Default Color Conversion Context
.XS
\*(SN Obtaining the Default Color Conversion Context
.XE
.LP
You can change the default CCC attributes for subsequently created CCCs
by changing the CCC attributes of the default CCC.
.IN "CCC" "default"
.IN "Color Conversion Context" "default"
A default CCC is associated with each screen.
.sp
.LP
To obtain the default CCC for a screen, use
.PN XcmsDefaultCCC .
.IN "XcmsDefaultCCC" "" "@DEF@"
.IN "Color Conversion Context" "default"
.IN "CCC" "default"
.sM
.FD 0
XcmsCCC XcmsDefaultCCC\^(\^\fIdisplay\fP, \fIscreen_number\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      int \fIscreen_number\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIscreen_number\fP 1i
Specifies the appropriate screen number on the host server.
.LP
.eM
The
.PN XcmsDefaultCCC
function returns the default CCC for the specified screen.
Its visual is the default visual of the screen.
Its initial gamut compression and white point
adjustment procedures as well as the associated client data are implementation
specific.
.NH 3
Color Conversion Context Macros
.XS
\*(SN Color Conversion Context Macros
.XE
.LP
Applications should not directly modify any part of the
.PN XcmsCCC .
The following lists the C language macros, their corresponding function
equivalents for other language bindings, and what data they both
can return.
.sp
.LP
.IN "DisplayOfCCC" "" "@DEF@"
.IN "XcmsDisplayOfCCC" "" "@DEF@"
.sM
.FD 0
DisplayOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.sp
Display *XcmsDisplayOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.LP
.eM
Both return the display associated with the specified CCC.
.LP
.sp
.IN "VisualOfCCC" "" "@DEF@"
.IN "XcmsVisualOfCCC" "" "@DEF@"
.sM
.FD 0
VisualOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.sp
Visual *XcmsVisualOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.LP
.eM
Both return the visual associated with the specified CCC.
.sp
.LP
.IN "ScreenNumberOfCCC" "" "@DEF@"
.IN "XcmsScreenNumberOfCCC" "" "@DEF@"
.sM
.FD 0
ScreenNumberOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.sp
int XcmsScreenNumberOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.LP
.eM
Both return the number of the screen associated with the specified CCC.
.sp
.LP
.IN "ScreenWhitePointOfCCC" "" "@DEF@"
.IN "XcmsScreenWhitePointOfCCC" "" "@DEF@"
.sM
.FD 0
ScreenWhitePointOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.sp
XcmsColor *XcmsScreenWhitePointOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.LP
.eM
Both return the white point of the screen associated with the specified CCC.
.sp
.LP
.IN "ClientWhitePointOfCCC" "" "@DEF@"
.IN "XcmsClientWhitePointOfCCC" "" "@DEF@"
.sM
.FD 0
ClientWhitePointOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.sp
XcmsColor *XcmsClientWhitePointOfCCC\^(\^\fIccc\fP\^)
.br
     XcmsCCC \fIccc\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.LP
.eM
Both return the Client White Point of the specified CCC.
.NH 3
Modifying Attributes of a Color Conversion Context
.XS
\*(SN Modifying Attributes of a Color Conversion Context
.XE
.LP
To set the Client White Point in the CCC, use
.PN XcmsSetWhitePoint .
.IN "XcmsSetWhitePoint" "" "@DEF@"
.IN "Client White Point" "of Color Conversion Context"
.sM
.FD 0
Status XcmsSetWhitePoint\^(\^\fIccc\fP\^, \fIcolor\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColor *\fIcolor\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.ds Co new Client White Point
.IP \fIcolor\fP 1i
Specifies the \*(Co.
.LP
.eM
The
.PN XcmsSetWhitePoint
function changes the Client White Point in the specified CCC.
Note that the pixel member is ignored 
and that the color specification is left unchanged upon return.
The format for the new white point must be
.PN XcmsCIEXYZFormat ,
.PN XcmsCIEuvYFormat ,
.PN XcmsCIExyYFormat ,
or
.PN XcmsUndefinedFormat .
If the color argument is NULL, this function sets the format component of the
Client White Point specification to
.PN XcmsUndefinedFormat ,
indicating that the Client White Point is assumed to be the same as the
Screen White Point.
.LP
This function returns nonzero status
if the format for the new white point is valid;
otherwise, it returns zero.

.sp
.LP
To set the gamut compression procedure and corresponding client data
in a specified CCC, use
.PN XcmsSetCompressionProc .
.IN "XcmsSetCompressionProc" "" "@DEF@"
.IN "Gamut compression" "setting in Color Conversion Context"
.IN "Gamut compression" "procedure"
.IN "Gamut compression" "client data"
.sM
.FD 0
XcmsCompressionProc XcmsSetCompressionProc\^(\^\fIccc\fP\^, \fIcompression_proc\fP\^, \fIclient_data\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsCompressionProc \fIcompression_proc\fP\^;
.br
      XPointer \fIclient_data\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.IP \fIcompression_proc\fP 1i
Specifies the gamut compression procedure that is to be applied 
when a color lies outside the screen's color gamut.
If NULL is specified and a function using this CCC must convert
a color specification to a device-dependent format and encounters a color
that lies outside the screen's color gamut, 
that function will return
.PN XcmsFailure .
.ds Cd the gamut compression procedure
.IP \fIclient_data\fP 1i
Specifies client data for \*(Cd or NULL.
.LP
.eM
The
.PN XcmsSetCompressionProc
function first sets the gamut compression procedure and client data 
in the specified CCC with the newly specified procedure and client data
and then returns the old procedure.
.sp
.LP
To set the white point adjustment procedure and corresponding client data
in a specified CCC, use
.PN XcmsSetWhiteAdjustProc .
.IN "XcmsSetWhiteAdjustProc" "" "@DEF@"
.IN "White point adjustment" "setting in Color Conversion Context"
.IN "White point adjustment" "procedure"
.IN "White point adjustment" "client data"
.FD 0
.sM
XcmsWhiteAdjustProc XcmsSetWhiteAdjustProc\^(\^\fIccc\fP\^, \fIwhite_adjust_proc\fP\^, \fIclient_data\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsWhiteAdjustProc \fIwhite_adjust_proc\fP\^;
.br
      XPointer \fIclient_data\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.IP \fIwhite_adjust_proc\fP 1i
Specifies the white point adjustment procedure.
.ds Cd the white point adjustment procedure
.IP \fIclient_data\fP 1i
Specifies client data for \*(Cd or NULL.
.LP
.eM
The
.PN XcmsSetWhiteAdjustProc
function first sets the white point adjustment procedure and client data 
in the specified CCC with the newly specified procedure and client data
and then returns the old procedure.
.NH 3
Creating and Freeing a Color Conversion Context
.XS
\*(SN Creating and Freeing a Color Conversion Context
.XE
.LP
You can explicitly create a CCC within your application by calling
.PN XcmsCreateCCC .
These created CCCs can then be used by those functions that explicitly
call for a CCC argument.
Old CCCs that will not be used by the application should be freed using
.PN XcmsFreeCCC .
.sp
.LP
To create a CCC, use
.PN XcmsCreateCCC .
.IN "XcmsCreateCCC" "" "@DEF@"
.IN "Color Conversion Context" "creation"
.IN "CCC" "creation"
.sM
.FD 0
XcmsCCC XcmsCreateCCC\^(\^\fIdisplay\fP, \fIscreen_number\fP\^, \fIvisual\fP\^, \fIclient_white_point\fP\^, \fIcompression_proc\fP\^,
.br
                    \fIcompression_client_data\fP\^, \fIwhite_adjust_proc\fP\^, \fIwhite_adjust_client_data\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      int \fIscreen_number\fP\^;
.br
      Visual *\fIvisual\fP\^;
.br
      XcmsColor *\fIclient_white_point\fP\^;
.br
      XcmsCompressionProc \fIcompression_proc\fP\^;
.br
      XPointer \fIcompression_client_data\fP\^;
.br
      XcmsWhiteAdjustProc \fIwhite_adjust_proc\fP\^;
.br
      XPointer \fIwhite_adjust_client_data\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIscreen_number\fP 1i
Specifies the appropriate screen number on the host server.
.IP \fIvisual\fP 1i
Specifies the visual type.
.IP \fIclient_white_point\fP 1i
Specifies the Client White Point.
If NULL is specified, 
the Client White Point is to be assumed to be the same as the
Screen White Point.
Note that the pixel member is ignored.
.IP \fIcompression_proc\fP 1i
Specifies the gamut compression procedure that is to be applied 
when a color lies outside the screen's color gamut.
If NULL is specified and a function using this CCC must convert
a color specification to a device-dependent format and encounters a color
that lies outside the screen's color gamut, 
that function will return
.PN XcmsFailure .
.IP \fIcompression_client_data\fP 1i
Specifies client data for use by the gamut compression procedure or NULL.
.IP \fIwhite_adjust_proc\fP 1i
Specifies the white adjustment procedure that is to be applied
when the Client White Point differs from the Screen White Point.
NULL indicates that no white point adjustment is desired.
.IP \fIwhite_adjust_client_data\fP 1i
Specifies client data for use with the white point adjustment procedure or NULL.
.LP
.eM
The
.PN XcmsCreateCCC
function creates a CCC for the specified display, screen, and visual.
.LP
.sp
To free a CCC, use
.PN XcmsFreeCCC .
.IN "XcmsFreeCCC" "" "@DEF@"
.IN "Color Conversion Context" "freeing"
.IN "CCC" "freeing"
.sM
.FD 0
void XcmsFreeCCC\^(\^\fIccc\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.LP
.eM
The
.PN XcmsFreeCCC
function frees the memory used for the specified CCC.
Note that default CCCs and those currently associated with colormaps
are ignored.
.NH 2
Converting between Color Spaces
.XS
\*(SN Converting between Color Spaces
.XE
.LP
.sp
To convert an array of color specifications in arbitrary color formats
to a single destination format, use
.PN XcmsConvertColors .
.IN "Color conversion"
.IN "Color" "conversion"
.IN "XcmsConvertColors" "" "@DEF@"
.sM
.FD 0
Status XcmsConvertColors\^(\^\fIccc\fP\^, \fIcolors_in_out\fP\^, \fIncolors\fP\^, \fItarget_format\fP\^, \fIcompression_flags_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColor \fIcolors_in_out\fP\^[\^]\^;
.br
      unsigned int \fIncolors\fP\^;
.br
      XcmsColorFormat \fItarget_format\fP\^;
.br
      Bool \fIcompression_flags_return\fP\^[\^]\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
If conversion is between device-independent color spaces only
(for example, TekHVC to CIELuv),
the CCC is necessary only to specify the Client White Point.
.IP \fIcolors_in_out\fP 1i
Specifies an array of color specifications.
Pixel members are ignored and remain unchanged upon return.
.IP \fIncolors\fP 1i
Specifies the number of 
.PN XcmsColor
structures in the color-specification array.
.IP \fItarget_format\fP 1i
Specifies the target color specification format.
.IP \fIcompression_flags_return\fP 1i
Returns an array of Boolean values indicating compression status.
If a non-NULL pointer is supplied,
each element of the array is set to
.PN True
if the corresponding color was compressed and
.PN False
otherwise.
Pass NULL if the compression status is not useful.
.LP
.eM
The
.PN XcmsConvertColors
function converts the color specifications in the specified array of
.PN XcmsColor
structures from their current format to a single target format,
using the specified CCC.
When the return value is
.PN XcmsFailure ,
the contents of the color specification array are left unchanged.
.LP
The array may contain a mixture of color specification formats
(for example, 3 CIE XYZ, 2 CIE Luv, and so on).
When the array contains both device-independent and
device-dependent color specifications and the target_format argument specifies
a device-dependent format (for example,
.PN XcmsRGBiFormat ,
.PN XcmsRGBFormat ),
all specifications are converted to CIE XYZ format and then to the target
device-dependent format.
.NH 2
Callback Functions
.XS
\*(SN Callback Functions
.XE
.LP
This section describes the gamut compression and white point
adjustment callbacks.
.LP
The gamut compression procedure specified in the CCC
is called when an attempt to convert a color specification from
.PN XcmsCIEXYZ
to a device-dependent format (typically
.PN XcmsRGBi )
results in a color that lies outside the screen's color gamut.
If the gamut compression procedure requires client data, this data is passed
via the gamut compression client data in the CCC.
.LP
During color specification conversion between device-independent
and device-dependent color spaces,
if a white point adjustment procedure is specified in the CCC,
it is triggered when the Client White Point and Screen White Point differ.
If required, the client data is obtained from the CCC.
.NH 3
Prototype Gamut Compression Procedure
.XS
\*(SN Prototype Gamut Compression Procedure
.XE
.LP
The gamut compression callback interface must adhere to the
following:
.IN "XcmsCompressionProc" "" "@DEF@"
.sM
.FD 0
typedef Status (*\^XcmsCompressionProc\^)\^(\^\fIccc\fP\^, \fIcolors_in_out\fP\^, \fIncolors\fP\^, \fIindex\fP\^, \fIcompression_flags_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColor \fIcolors_in_out[]\fP\^;
.br
      unsigned int \fIncolors\fP\^;
.br
      unsigned int \fIindex\fP\^;
.br
      Bool \fIcompression_flags_return[]\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.IP \fIcolors_in_out\fP 1i
Specifies an array of color specifications.
Pixel members should be ignored and must remain unchanged upon return.
.IP \fIncolors\fP 1i
Specifies the number of 
.PN XcmsColor
structures in the color-specification array.
.IP \fIindex\fP 1i
Specifies the index into the array of
.PN XcmsColor
structures for the encountered color specification that lies outside the 
screen's color gamut.
Valid values are 0 (for the first element) to ncolors \- 1.
.IP \fIcompression_flags_return\fP 1i
Returns an array of Boolean values for indicating compression status.
If a non-NULL pointer is supplied
and a color at a given index is compressed, then
.PN True
should be stored at the corresponding index in this array;
otherwise, the array should not be modified.
.LP
.eM
When implementing a gamut compression procedure, consider the following
rules and assumptions:
.IP \(bu 5
The gamut compression procedure can attempt to compress one or multiple
specifications at a time.
.IP \(bu 5
When called, elements 0 to index \- 1 in the color specification
array can be assumed to fall within the screen's color gamut.
In addition, these color specifications are already in some device-dependent
format (typically
.PN XcmsRGBi ).
If any modifications are made to these color specifications,
they must be in their initial device-dependent format upon return.
.IP \(bu 5
When called, the element in the color specification array specified
by the index argument contains the color specification outside the 
screen's color gamut encountered by the calling routine.
In addition, this color specification can be assumed to be in
.PN XcmsCIEXYZ .
Upon return, this color specification must be in
.PN XcmsCIEXYZ .
.IP \(bu 5
When called, elements from index to ncolors \- 1 
in the color specification array may or may not fall within the
screen's color gamut.
In addition, these color specifications can be assumed to be in
.PN XcmsCIEXYZ .
If any modifications are made to these color specifications, 
they must be in
.PN XcmsCIEXYZ
upon return.
.IP \(bu 5
The color specifications passed to the gamut compression procedure
have already been adjusted to the Screen White Point.
This means that at this point the color specification's white point
is the Screen White Point.
.IP \(bu 5
If the gamut compression procedure uses a device-independent color space not
initially accessible for use in the color management system, use 
.PN XcmsAddColorSpace
to ensure that it is added.
.NH 3
Supplied Gamut Compression Procedures
.XS
\*(SN Supplied Gamut Compression Procedures
.XE
.LP
The following equations are useful in describing gamut compression
functions:
.EQ
delim %%
.EN
.LP
.Ds 0
%CIELab~Psychometric~Chroma ~=~ sqrt(a_star sup 2 ~+~ b_star sup 2 )%

%CIELab~Psychometric~Hue ~=~ tan sup -1 left [ b_star over a_star right ]%

%CIELuv~Psychometric~Chroma ~=~ sqrt(u_star sup 2 ~+~ v_star sup 2 )%

%CIELuv~Psychometric~Hue ~=~ tan sup -1 left [ v_star over u_star right ]%
.De
.LP
The gamut compression callback procedures provided by Xlib are as follows:
.IP \(bu 5
.PN XcmsCIELabClipL
.IP
This brings the encountered out-of-gamut color specification into the 
screen's color gamut by reducing or increasing CIE metric lightness (L*) 
in the CIE L*a*b* color space until the color is within the gamut.
If the Psychometric Chroma of the color specification 
is beyond maximum for the Psychometric Hue Angle,
then while maintaining the same Psychometric Hue Angle,
the color will be clipped to the CIE L*a*b* coordinates of maximum
Psychometric Chroma.
See
.PN XcmsCIELabQueryMaxC .
No client data is necessary.
.IP \(bu 5
.PN XcmsCIELabClipab
.IP
This brings the encountered out-of-gamut color specification into the 
screen's color gamut by reducing Psychometric Chroma,
while maintaining Psychometric Hue Angle,
until the color is within the gamut.
No client data is necessary.
.IP \(bu 5
.PN XcmsCIELabClipLab
.IP
This brings the encountered out-of-gamut color specification into the
screen's color gamut by replacing it with CIE L*a*b* coordinates
that fall within the color gamut while maintaining the original
Psychometric Hue
Angle and whose vector to the original coordinates is the shortest attainable.
No client data is necessary.
.IP \(bu 5
.PN XcmsCIELuvClipL
.IP
This brings the encountered out-of-gamut color specification into the 
screen's color gamut by reducing or increasing CIE metric lightness (L*)
in the CIE L*u*v* color space until the color is within the gamut.
If the Psychometric Chroma of the color specification
is beyond maximum for the Psychometric Hue Angle,
then, while maintaining the same Psychometric Hue Angle,
the color will be clipped to the CIE L*u*v* coordinates of maximum
Psychometric Chroma.
See
.PN XcmsCIELuvQueryMaxC .
No client data is necessary.
.IP \(bu 5
.PN XcmsCIELuvClipuv
.IP
This brings the encountered out-of-gamut color specification into the
screen's color gamut by reducing
Psychometric Chroma, while maintaining Psychometric Hue Angle,
until the color is within the gamut.
No client data is necessary.
.IP \(bu 5
.PN XcmsCIELuvClipLuv
.IP
This brings the encountered out-of-gamut color specification into the
screen's color gamut by replacing it with CIE L*u*v* coordinates
that fall within the color gamut while maintaining the original
Psychometric Hue
Angle and whose vector to the original coordinates is the shortest attainable.
No client data is necessary.
.IP \(bu 5
.PN XcmsTekHVCClipV
.IP
This brings the encountered out-of-gamut color specification into the
screen's color gamut by reducing or increasing the Value dimension
in the TekHVC color space until the color is within the gamut.
If Chroma of the color specification is beyond maximum for the particular Hue,
then, while maintaining the same Hue,
the color will be clipped to the Value and Chroma coordinates
that represent maximum Chroma for that particular Hue.
No client data is necessary.
.IP \(bu 5
.PN XcmsTekHVCClipC
.IP
This brings the encountered out-of-gamut color specification into the
screen's color gamut by reducing the Chroma dimension
in the TekHVC color space until the color is within the gamut.
No client data is necessary.
.IP \(bu 5
.PN XcmsTekHVCClipVC
.IP
This brings the encountered out-of-gamut color specification into the
screen's color gamut by replacing it with TekHVC coordinates
that fall within the color gamut while maintaining the original Hue
and whose vector to the original coordinates is the shortest attainable.
No client data is necessary.
.NH 3
Prototype White Point Adjustment Procedure
.XS
\*(SN Prototype White Point Adjustment Procedure
.XE
.LP
The white point adjustment procedure interface must adhere to the following:
.IN "XcmsWhiteAdjustProc" "" "@DEF@"
.sM
.FD 0
typedef Status (*\^XcmsWhiteAdjustProc\^)\^(\^\fIccc\fP\^, \fIinitial_white_point\fP\^, \fItarget_white_point\fP\^, \fItarget_format\fP\^,
.br
                \fIcolors_in_out\fP\^, \fIncolors\fP\^, \fIcompression_flags_return\fP\^)
.br
       XcmsCCC \fIccc\fP\^;
.br
       XcmsColor *\fIinitial_white_point\fP\^;
.br
       XcmsColor *\fItarget_white_point\fP\^;
.br
       XcmsColorFormat \fItarget_format\fP\^;
.br
       XcmsColor \fIcolors_in_out[]\fP\^;
.br
       unsigned int \fIncolors\fP\^;
.br
       Bool \fIcompression_flags_return[]\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.IP \fIinitial_white_point\fP 1i
Specifies the initial white point.
.IP \fItarget_white_point\fP 1i
Specifies the target white point.
.IP \fItarget_format\fP 1i
Specifies the target color specification format.
.IP \fIcolors_in_out\fP 1i
Specifies an array of color specifications.
Pixel members should be ignored and must remain unchanged upon return.
.IP \fIncolors\fP 1i
Specifies the number of 
.PN XcmsColor
structures in the color-specification array.
.IP \fIcompression_flags_return\fP 1i
Returns an array of Boolean values for indicating compression status.
If a non-NULL pointer is supplied
and a color at a given index is compressed, then
.PN True
should be stored at the corresponding index in this array;
otherwise, the array should not be modified.
.LP
.eM
.NH 3
Supplied White Point Adjustment Procedures
.XS
\*(SN Supplied White Point Adjustment Procedures
.XE
.LP
White point adjustment procedures provided by Xlib are as follows:
.IP \(bu 5
.PN XcmsCIELabWhiteShiftColors
.IP
This uses the CIE L*a*b* color space for adjusting the chromatic character
of colors to compensate for the chromatic differences between the source
and destination white points.
This procedure simply converts the color specifications to 
.PN XcmsCIELab
using the source white point and then converts to the target specification
format using the destination's white point.
No client data is necessary.
.IP \(bu 5
.PN XcmsCIELuvWhiteShiftColors
.IP
This uses the CIE L*u*v* color space for adjusting the chromatic character
of colors to compensate for the chromatic differences between the source
and destination white points.
This procedure simply converts the color specifications to 
.PN XcmsCIELuv
using the source white point and then converts to the target specification
format using the destination's white point.
No client data is necessary.
.IP \(bu 5
.PN XcmsTekHVCWhiteShiftColors
.IP
This uses the TekHVC color space for adjusting the chromatic character
of colors to compensate for the chromatic differences between the source
and destination white points.
This procedure simply converts the color specifications to
.PN XcmsTekHVC
using the source white point and then converts to the target specification
format using the destination's white point.
An advantage of this procedure over those previously described
is an attempt to minimize hue shift.
No client data is necessary.
.LP
From an implementation point of view,
these white point adjustment procedures convert the color specifications
to a device-independent but white-point-dependent color space 
(for example, CIE L*u*v*, CIE L*a*b*, TekHVC) using one white point
and then converting those specifications to the target color space 
using another white point.
In other words,
the specification goes in the color space with one white point 
but comes out with another white point, 
resulting in a chromatic shift based on the chromatic displacement
between the initial white point and target white point.
The CIE color spaces that are assumed to be white-point-independent
are CIE u'v'Y, CIE XYZ, and CIE xyY.
When developing a custom white point adjustment procedure that uses a
device-independent color space not initially accessible for use in the
color management system, use
.PN XcmsAddColorSpace
to ensure that it is added.
.LP
As an example, 
if the CCC specifies a white point adjustment procedure
and if the Client White Point and Screen White Point differ, the
.PN XcmsAllocColor
function will use the white point adjustment
procedure twice: 
.IP \(bu 5
Once to convert to
.PN XcmsRGB
.IP \(bu  5
A second time to convert from
.PN XcmsRGB 
.LP
For example, assume the specification is in
.PN XcmsCIEuvY
and the adjustment procedure is
.PN XcmsCIELuvWhiteShiftColors .
During conversion to
.PN XcmsRGB ,
the call to 
.PN XcmsAllocColor 
results in the following series of color specification conversions:
.\" Do these need to be font coded?
.IP \(bu 5
From 
.PN XcmsCIEuvY
to
.PN XcmsCIELuv
using the Client White Point
.IP \(bu 5
From 
.PN XcmsCIELuv
to
.PN XcmsCIEuvY
using the Screen White Point
.IP \(bu 5
From
.PN XcmsCIEuvY
to
.PN XcmsCIEXYZ
(CIE u'v'Y and XYZ are white-point-independent color spaces)
.IP \(bu 5
From 
.PN XcmsCIEXYZ
to 
.PN XcmsRGBi
.IP \(bu 5
From 
.PN XcmsRGBi
to
.PN XcmsRGB
.LP
The resulting RGB specification is passed to
.PN XAllocColor ,
and the RGB
specification returned by
.PN XAllocColor
is converted back to 
.PN XcmsCIEuvY
by reversing the color conversion sequence.
.NH 2
Gamut Querying Functions
.XS
\*(SN Gamut Querying Functions
.XE
.LP
This section describes the gamut querying functions that Xlib provides.
These functions allow the client to query the boundary 
of the screen's color gamut in terms of the CIE L*a*b*, CIE L*u*v*, 
and TekHVC color spaces.
.IN "Gamut querying"
Functions are also provided that allow you to query 
the color specification of:
.IP \(bu 5
White (full-intensity red, green, and blue)
.IP \(bu 5
Red (full-intensity red while green and blue are zero)
.IP \(bu 5
Green (full-intensity green while red and blue are zero)
.IP \(bu 5
Blue (full-intensity blue while red and green are zero)
.IP \(bu 5
Black (zero-intensity red, green, and blue)
.LP
The white point associated with color specifications passed to 
and returned from these gamut querying
functions is assumed to be the Screen White Point.
.IN "Screen White Point"
This is a reasonable assumption,
because the client is trying to query the screen's color gamut.
.LP
The following naming convention is used for the Max and Min functions:
.LP
.Ds 0
Xcms\fI<color_space>\fPQueryMax\fI<dimensions>\fP

Xcms\fI<color_space>\fPQueryMin\fI<dimensions>\fP
.De
.LP
The <dimensions> consists of a letter or letters 
that identify the dimensions of the color space 
that are not fixed.
For example, 
.PN XcmsTekHVCQueryMaxC
is given a fixed Hue and Value for which maximum Chroma is found.
.NH 3
Red, Green, and Blue Queries
.XS
\*(SN Red, Green, and Blue Queries
.XE
.LP
To obtain the color specification for black 
(zero-intensity red, green, and blue), use
.PN XcmsQueryBlack .
.IN "XcmsQueryBlack" "" "@DEF@"
.sM
.FD 0
Status XcmsQueryBlack\^(\^\fIccc\fP\^, \fItarget_format\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColorFormat \fItarget_format\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.IP \fItarget_format\fP 1i
Specifies the target color specification format.
.ds Cs zero-intensity red, green, and blue
.IP \fIcolor_return\fP 1i
Returns the color specification in the specified target format
for \*(Cs.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsQueryBlack
function returns the color specification in the specified target format
for zero-intensity red, green, and blue.
.sp
.LP
To obtain the color specification for blue 
(full-intensity blue while red and green are zero), use
.PN XcmsQueryBlue .
.IN "XcmsQueryBlue" "" "@DEF@"
.sM
.FD 0
Status XcmsQueryBlue\^(\^\fIccc\fP\^, \fItarget_format\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColorFormat \fItarget_format\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.IP \fItarget_format\fP 1i
Specifies the target color specification format.
.ds Cs full-intensity blue while red and green are zero
.IP \fIcolor_return\fP 1i
Returns the color specification in the specified target format
for \*(Cs.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsQueryBlue
function returns the color specification in the specified target format
for full-intensity blue while red and green are zero.
.sp
.LP
To obtain the color specification for green
(full-intensity green while red and blue are zero), use
.PN XcmsQueryGreen .
.IN "XcmsQueryGreen" "" "@DEF@"
.sM
.FD 0
Status XcmsQueryGreen\^(\^\fIccc\fP\^, \fItarget_format\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColorFormat \fItarget_format\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.IP \fItarget_format\fP 1i
Specifies the target color specification format.
.ds Cs full-intensity green while red and blue are zero
.IP \fIcolor_return\fP 1i
Returns the color specification in the specified target format
for \*(Cs.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsQueryGreen
function returns the color specification in the specified target format
for full-intensity green while red and blue are zero.
.sp
.LP
To obtain the color specification for red
(full-intensity red while green and blue are zero), use
.PN XcmsQueryRed .
.IN "XcmsQueryRed" "" "@DEF@"
.sM
.FD 0
Status XcmsQueryRed\^(\^\fIccc\fP\^, \fItarget_format\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColorFormat \fItarget_format\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.IP \fItarget_format\fP 1i
Specifies the target color specification format.
.ds Cs full-intensity red while green and blue are zero
.IP \fIcolor_return\fP 1i
Returns the color specification in the specified target format
for \*(Cs.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsQueryRed
function returns the color specification in the specified target format
for full-intensity red while green and blue are zero.
.LP
.sp
To obtain the color specification for white
(full-intensity red, green, and blue), use
.PN XcmsQueryWhite .
.IN "XcmsQueryWhite" "" "@DEF@"
.sM
.FD 0
Status XcmsQueryWhite\^(\^\fIccc\fP\^, \fItarget_format\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColorFormat \fItarget_format\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.IP \fItarget_format\fP 1i
Specifies the target color specification format.
.ds Cs full-intensity red, green, and blue
.IP \fIcolor_return\fP 1i
Returns the color specification in the specified target format
for \*(Cs.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsQueryWhite
function returns the color specification in the specified target format
for full-intensity red, green, and blue.
.NH 3
CIELab Queries
.XS
\*(SN CIELab Queries
.XE
.LP
The following equations are useful in describing the CIELab query functions:
.EQ
delim %%
.EN
.LP
.IN "Psychometric Hue Angle"
.IN "CIE metric lightness"
.IN "Psychometric Chroma"
.IN "Psychometric Chroma" "maximum"
.Ds 0
%CIELab~Psychometric~Chroma ~=~ sqrt(a_star sup 2 ~+~ b_star sup 2 )%

%CIELab~Psychometric~Hue ~=~ tan sup -1 left [ b_star over a_star right ]%
.De
.sp
To obtain the CIE L*a*b* coordinates of maximum Psychometric Chroma
for a given Psychometric Hue Angle and CIE metric lightness (L*), use
.PN XcmsCIELabQueryMaxC .
.IN "XcmsCIELabQueryMaxC" "" "@DEF@"
.sM
.FD 0
Status XcmsCIELabQueryMaxC\^(\^\fIccc\fP\^, \fIhue_angle\fP\^, \fIL_star\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue_angle\fP\^;
.br
      XcmsFloat \fIL_star\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Ha maximum chroma
.IP \fIhue_angle\fP 1i
Specifies the hue angle (in degrees) at which to find \*(Ha.
.ds Ls maximum chroma
.IP \fIL_star\fP 1i
Specifies the lightness (L*) at which to find \*(Ls.
.ds Lc maximum chroma
.ds lC hue angle and lightness
.IP \fIcolor_return\fP 1i
Returns the CIE L*a*b* coordinates of \*(Lc
displayable by the screen for the given \*(lC.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsCIELabQueryMaxC
function, given a hue angle and lightness,
finds the point of maximum chroma displayable by the screen.
It returns this point in CIE L*a*b* coordinates.
.LP
.sp
To obtain the CIE L*a*b* coordinates of maximum CIE metric lightness (L*)
for a given Psychometric Hue Angle and Psychometric Chroma, use
.PN XcmsCIELabQueryMaxL .
.IN "Psychometric Hue Angle"
.IN "CIE metric lightness"
.IN "CIE metric lightness" "maximum"
.IN "XcmsCIELabQueryMaxL" "" "@DEF@"
.sM
.FD 0
Status XcmsCIELabQueryMaxL\^(\^\fIccc\fP\^, \fIhue_angle\fP\^, \fIchroma\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue_angle\fP\^;
.br
      XcmsFloat \fIchroma\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Ha maximum lightness
.IP \fIhue_angle\fP 1i
Specifies the hue angle (in degrees) at which to find \*(Ha.
.ds Ch maximum lightness
.IP \fIchroma\fP 1i
Specifies the chroma at which to find \*(Ch.
.ds Lc maximum lightness
.ds lC hue angle and chroma
.IP \fIcolor_return\fP 1i
Returns the CIE L*a*b* coordinates of \*(Lc
displayable by the screen for the given \*(lC.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsCIELabQueryMaxL
function, given a hue angle and chroma,
finds the point in CIE L*a*b* color space of maximum 
lightness (L*) displayable by the screen.
It returns this point in CIE L*a*b* coordinates.
An 
.PN XcmsFailure
return value usually indicates that the given chroma
is beyond maximum for the given hue angle.
.sp
.LP
To obtain the CIE L*a*b* coordinates of maximum Psychometric Chroma
for a given Psychometric Hue Angle, use
.PN XcmsCIELabQueryMaxLC .
.IN "Psychometric Hue Angle"
.IN "Psychometric Chroma"
.IN "CIE metric lightness"
.IN "Psychometric Chroma" "maximum"
.IN "CIE metric lightness" "maximum"
.IN "XcmsCIELabQueryMaxLC" "" "@DEF@"
.sM
.FD 0
Status XcmsCIELabQueryMaxLC\^(\^\fIccc\fP\^, \fIhue_angle\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue_angle\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Ha maximum chroma
.IP \fIhue_angle\fP 1i
Specifies the hue angle (in degrees) at which to find \*(Ha.
.ds Lc maximum chroma
.ds lC hue angle
.IP \fIcolor_return\fP 1i
Returns the CIE L*a*b* coordinates of \*(Lc
displayable by the screen for the given \*(lC.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsCIELabQueryMaxLC
function, given a hue angle,
finds the point of maximum chroma displayable by the screen.
It returns this point in CIE L*a*b* coordinates.
.sp
.LP
To obtain the CIE L*a*b* coordinates of minimum CIE metric lightness (L*)
for a given Psychometric Hue Angle and Psychometric Chroma, use
.PN XcmsCIELabQueryMinL .
.IN "Psychometric Hue Angle"
.IN "CIE metric lightness"
.IN "CIE metric lightness" "minimum"
.IN "XcmsCIELabQueryMinL" "" "@DEF@"
.sM
.FD 0
Status XcmsCIELabQueryMinL\^(\^\fIccc\fP\^, \fIhue_angle\fP\^, \fIchroma\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue_angle\fP\^;
.br
      XcmsFloat \fIchroma\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Ha minimum lightness
.IP \fIhue_angle\fP 1i
Specifies the hue angle (in degrees) at which to find \*(Ha.
.ds Ch minimum lightness
.IP \fIchroma\fP 1i
Specifies the chroma at which to find \*(Ch.
.ds Lc minimum lightness
.ds lC hue angle and chroma
.IP \fIcolor_return\fP 1i
Returns the CIE L*a*b* coordinates of \*(Lc
displayable by the screen for the given \*(lC.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsCIELabQueryMinL
function, given a hue angle and chroma,
finds the point of minimum lightness (L*) displayable by the screen.
It returns this point in CIE L*a*b* coordinates.
An 
.PN XcmsFailure
return value usually indicates that the given chroma
is beyond maximum for the given hue angle.
.NH 3
CIELuv Queries
.XS
\*(SN CIELuv Queries
.XE
.LP
The following equations are useful in describing the CIELuv query functions:
.EQ
delim %%
.EN
.LP
.IN "Psychometric Hue Angle"
.IN "CIE metric lightness"
.IN "Psychometric Chroma"
.IN "Psychometric Chroma" "maximum"
.Ds 0
%CIELuv~Psychometric~Chroma ~=~ sqrt(u_star sup 2 ~+~ v_star sup 2 )%

%CIELuv~Psychometric~Hue ~=~ tan sup -1 left [ v_star over u_star right ]%
.De
.sp
.LP
To obtain the CIE L*u*v* coordinates of maximum Psychometric Chroma
for a given Psychometric Hue Angle and CIE metric lightness (L*), use
.PN XcmsCIELuvQueryMaxC .
.IN "XcmsCIELuvQueryMaxC" "" "@DEF@"
.sM
.FD 0
Status XcmsCIELuvQueryMaxC\^(\^\fIccc\fP\^, \fIhue_angle\fP\^, \fIL_star\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue_angle\fP\^;
.br
      XcmsFloat \fIL_star\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Ha maximum chroma
.IP \fIhue_angle\fP 1i
Specifies the hue angle (in degrees) at which to find \*(Ha.
.ds Ls maximum chroma
.IP \fIL_star\fP 1i
Specifies the lightness (L*) at which to find \*(Ls.
.ds Lc maximum chroma
.ds lC hue angle and lightness
.IP \fIcolor_return\fP 1i
Returns the CIE L*u*v* coordinates of \*(Lc
displayable by the screen for the given \*(lC.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsCIELuvQueryMaxC
function, given a hue angle and lightness,
finds the point of maximum chroma displayable by the screen.
It returns this point in CIE L*u*v* coordinates.
.sp
.LP
To obtain the CIE L*u*v* coordinates of maximum CIE metric lightness (L*)
for a given Psychometric Hue Angle and Psychometric Chroma, use
.PN XcmsCIELuvQueryMaxL .
.IN "Psychometric Hue Angle"
.IN "CIE metric lightness"
.IN "CIE metric lightness" "maximum"
.IN "XcmsCIELuvQueryMaxL" "" "@DEF@"
.sM
.FD 0
Status XcmsCIELuvQueryMaxL\^(\^\fIccc\fP\^, \fIhue_angle\fP\^, \fIchroma\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue_angle\fP\^;
.br
      XcmsFloat \fIchroma\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Ha maximum lightness
.IP \fIhue_angle\fP 1i
Specifies the hue angle (in degrees) at which to find \*(Ha.
.ds Ls maximum lightness
.IP \fIL_star\fP 1i
Specifies the lightness (L*) at which to find \*(Ls.
.ds Lc maximum lightness
.ds lC hue angle and chroma
.IP \fIcolor_return\fP 1i
Returns the CIE L*u*v* coordinates of \*(Lc
displayable by the screen for the given \*(lC.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsCIELuvQueryMaxL
function, given a hue angle and chroma,
finds the point in CIE L*u*v* color space of maximum 
lightness (L*) displayable by the screen.
It returns this point in CIE L*u*v* coordinates.
An 
.PN XcmsFailure
return value usually indicates that the given chroma
is beyond maximum for the given hue angle.
.sp
.LP
To obtain the CIE L*u*v* coordinates of maximum Psychometric Chroma
for a given Psychometric Hue Angle, use
.PN XcmsCIELuvQueryMaxLC .
.IN "Psychometric Hue Angle"
.IN "Psychometric Chroma"
.IN "CIE metric lightness"
.IN "Psychometric Chroma" "maximum"
.IN "CIE metric lightness" "maximum"
.IN "XcmsCIELuvQueryMaxLC" "" "@DEF@"
.sM
.FD 0
Status XcmsCIELuvQueryMaxLC\^(\^\fIccc\fP\^, \fIhue_angle\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue_angle\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Ha maximum chroma
.IP \fIhue_angle\fP 1i
Specifies the hue angle (in degrees) at which to find \*(Ha.
.ds Lc maximum chroma
.ds lC hue angle
.IP \fIcolor_return\fP 1i
Returns the CIE L*u*v* coordinates of \*(Lc
displayable by the screen for the given \*(lC.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsCIELuvQueryMaxLC
function, given a hue angle,
finds the point of maximum chroma displayable by the screen.
It returns this point in CIE L*u*v* coordinates.
.sp
.LP
To obtain the CIE L*u*v* coordinates of minimum CIE metric lightness (L*)
for a given Psychometric Hue Angle and Psychometric Chroma, use
.PN XcmsCIELuvQueryMinL .
.IN "Psychometric Hue Angle"
.IN "CIE metric lightness"
.IN "CIE metric lightness" "minimum"
.IN "XcmsCIELuvQueryMinL" "" "@DEF@"
.sM
.FD 0
Status XcmsCIELuvQueryMinL\^(\^\fIccc\fP\^, \fIhue_angle\fP\^, \fIchroma\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue_angle\fP\^;
.br
      XcmsFloat \fIchroma\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Ha minimum lightness
.IP \fIhue_angle\fP 1i
Specifies the hue angle (in degrees) at which to find \*(Ha.
.ds Ch minimum lightness
.IP \fIchroma\fP 1i
Specifies the chroma at which to find \*(Ch.
.ds Lc minimum lightness
.ds lC hue angle and chroma
.IP \fIcolor_return\fP 1i
Returns the CIE L*u*v* coordinates of \*(Lc
displayable by the screen for the given \*(lC.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM
The
.PN XcmsCIELuvQueryMinL
function, given a hue angle and chroma,
finds the point of minimum lightness (L*) displayable by the screen.
It returns this point in CIE L*u*v* coordinates.
An 
.PN XcmsFailure
return value usually indicates that the given chroma
is beyond maximum for the given hue angle.
.NH 3
TekHVC Queries
.XS
\*(SN TekHVC Queries
.XE
.LP
To obtain the maximum Chroma for a given Hue and Value, use
.PN XcmsTekHVCQueryMaxC .
.IN "Chroma"
.IN "Chroma" "maximum"
.IN "XcmsTekHVCQueryMaxC" "" "@DEF@"
.sM
.FD 0
Status XcmsTekHVCQueryMaxC\^(\^\fIccc\fP\^, \fIhue\fP\^, \fIvalue\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue\fP\^;
.br
      XcmsFloat \fIvalue\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Hu in which to find the maximum Chroma
.IP \fIhue\fP 1i
Specifies the Hue \*(Hu.
.ds Va maximum Chroma
.IP \fIvalue\fP 1i
Specifies the Value in which to find the \*(Va.
.ds Lc maximum Chroma along with the actual Hue and Value 
.ds lC maximum Chroma
.IP \fIcolor_return\fP 1i
Returns the \*(Lc at which the \*(lC was found.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsTekHVCQueryMaxC
function, given a Hue and Value,
determines the maximum Chroma in TekHVC color space
displayable by the screen.
It returns the maximum Chroma along with the actual Hue
and Value at which the maximum Chroma was found.
.sp
.LP
To obtain the maximum Value for a given Hue and Chroma, use
.PN XcmsTekHVCQueryMaxV .
.IN "Value"
.IN "Value" "maximum"
.IN "XcmsTekHVCQueryMaxV" "" "@DEF@"
.sM
.FD 0
Status XcmsTekHVCQueryMaxV\^(\^\fIccc\fP\^, \fIhue\fP\^, \fIchroma\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue\fP\^;
.br
      XcmsFloat \fIchroma\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Hu in which to find the maximum Value
.IP \fIhue\fP 1i
Specifies the Hue \*(Hu.
.ds Ch maximum Value
.IP \fIchroma\fP 1i
Specifies the chroma at which to find \*(Ch.
.ds Lc maximum Value along with the Hue and Chroma
.ds lC maximum Value
.IP \fIcolor_return\fP 1i
Returns the \*(Lc at which the \*(lC was found.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsTekHVCQueryMaxV
function, given a Hue and Chroma,
determines the maximum Value in TekHVC color space
displayable by the screen.
It returns the maximum Value and the actual Hue and Chroma
at which the maximum Value was found.
.sp
.LP
To obtain the maximum Chroma and Value at which it is reached
for a specified Hue, use
.PN XcmsTekHVCQueryMaxVC .
.IN "Chroma"
.IN "Value"
.IN "Chroma"  "maximum"
.IN "Value" "maximum"
.IN "XcmsTekHVCQueryMaxVC" "" "@DEF@"
.sM
.FD 0
Status XcmsTekHVCQueryMaxVC\^(\^\fIccc\fP\^, \fIhue\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Hu in which to find the maximum Chroma
.IP \fIhue\fP 1i
Specifies the Hue \*(Hu.
.ds Lc color specification in \
XcmsTekHVC for the maximum Chroma, the Value at which \
that maximum Chroma is reached, and the actual Hue
.ds lC maximum Chroma
.IP \fIcolor_return\fP 1i
Returns the \*(Lc at which the \*(lC was found.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsTekHVCQueryMaxVC
function, given a Hue,
determines the maximum Chroma in TekHVC color space displayable by the screen
and the Value at which that maximum Chroma is reached.
It returns the maximum Chroma,
the Value at which that maximum Chroma is reached,
and the actual Hue for which the maximum Chroma was found.
.sp
.LP
To obtain a specified number of TekHVC specifications such that they
contain maximum Values for a specified Hue and the
Chroma at which the maximum Values are reached, use
.PN XcmsTekHVCQueryMaxVSamples .
.IN "Chroma"
.IN "Value"
.IN "Chroma"  "maximum"
.IN "Value" "maximum"
.IN "XcmsTekHVCQueryMaxVSamples" "" "@DEF@"
.sM
.FD 0
Status XcmsTekHVCQueryMaxVSamples\^(\^\fIccc\fP\^, \fIhue\fP\^, \fIcolors_return\fP\^, \fInsamples\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue\fP\^;
.br
      XcmsColor \fIcolors_return[]\fP\^;
.br
      unsigned int \fInsamples\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Hu for maximum Chroma/Value samples
.IP \fIhue\fP 1i
Specifies the Hue \*(Hu.
.IP \fInsamples\fP 1i
Specifies the number of samples.
.IP \fIcolors_return\fP 1i
Returns nsamples of color specifications in XcmsTekHVC
such that the Chroma is the maximum attainable for the Value and Hue.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsTekHVCQueryMaxVSamples
returns nsamples of maximum Value, the Chroma at which that maximum Value
is reached, and the actual Hue for which the maximum Chroma was found.
These sample points may then be used to plot the maximum Value/Chroma
boundary of the screen's color gamut for the specified Hue in TekHVC color
space.
.sp
.LP
To obtain the minimum Value for a given Hue and Chroma, use
.PN XcmsTekHVCQueryMinV .
.IN "Value"
.IN "Value" "minimum"
.IN "XcmsTekHVCQueryMinV" "" "@DEF@"
.sM
.FD 0
Status XcmsTekHVCQueryMinV\^(\^\fIccc\fP\^, \fIhue\fP\^, \fIchroma\fP\^, \fIcolor_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsFloat \fIhue\fP\^;
.br
      XcmsFloat \fIchroma\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
The CCC's Client White Point and white point adjustment procedures
are ignored.
.ds Hu in which to find the minimum Value
.IP \fIhue\fP 1i
Specifies the Hue \*(Hu.
.ds Va minimum Value
.IP \fIvalue\fP 1i
Specifies the Value in which to find the \*(Va.
.ds Lc minimum Value and the actual Hue and Chroma
.ds lC minimum Value
.IP \fIcolor_return\fP 1i
Returns the \*(Lc at which the \*(lC was found.
The white point associated with the returned
color specification is the Screen White Point.
The value returned in the pixel member is undefined.
.LP
.eM 
The
.PN XcmsTekHVCQueryMinV
function, given a Hue and Chroma,
determines the minimum Value in TekHVC color space displayable by the screen.
It returns the minimum Value and the actual Hue and Chroma at which
the minimum Value was found.
.NH 2
Color Management Extensions
.XS
\*(SN Color Management Extensions
.XE
.LP
The Xlib color management facilities can be extended in two ways:
.IP \(bu 5
Device-Independent Color Spaces
.IP
Device-independent color spaces that are derivable to CIE XYZ
space can be added using the
.PN XcmsAddColorSpace
function.
.IP \(bu 5
Color Characterization Function Set
.IP
A Color Characterization Function Set consists of
device-dependent color spaces and their functions that
convert between these color spaces and the CIE XYZ
color space, bundled together for a specific class of output devices.
A function set can be added using the
.PN XcmsAddFunctionSet
function.
.NH 3
Color Spaces
.XS
\*(SN Color Spaces
.XE
.LP
The CIE XYZ color space serves as the hub for all
conversions between device-independent and device-dependent color spaces.
Therefore, the knowledge to convert an 
.PN XcmsColor
structure to and from CIE XYZ format is associated with each color space.
For example, conversion from CIE L*u*v* to RGB requires the knowledge
to convert from CIE L*u*v* to CIE XYZ and from CIE XYZ to RGB.
This knowledge is stored as an array of functions that,
when applied in series, will convert the 
.PN XcmsColor
structure to or from CIE XYZ format.
This color specification conversion mechanism facilitates
the addition of color spaces.
.LP
Of course, when converting between only device-independent color spaces
or only device-dependent color spaces,
shortcuts are taken whenever possible.
For example, conversion from TekHVC to CIE L*u*v* is performed 
by intermediate conversion to CIE u*v*Y and then to CIE L*u*v*, 
thus bypassing conversion between CIE u*v*Y and CIE XYZ.
.NH 3
Adding Device-Independent Color Spaces
.XS
\*(SN Adding Device-Independent Color Spaces
.XE
.LP
To add a device-independent color space, use
.PN XcmsAddColorSpace .
.IN  "XcmsAddColorSpace" "" "@DEF@"
.sM
.FD 0
Status XcmsAddColorSpace\^(\^\fIcolor_space\fP\^)
.br
      XcmsColorSpace *\fIcolor_space\fP\^;
.FN
.IP \fIcolor_space\fP 1i
Specifies the device-independent color space to add.
.LP
.eM
The
.PN XcmsAddColorSpace
function makes a device-independent color space (actually an
.PN XcmsColorSpace
structure) accessible by the color management system.
Because format values for unregistered color spaces are assigned at run time,
they should be treated as private to the client.
If references to an unregistered color space must be made
outside the client (for example, storing color specifications 
in a file using the unregistered color space), 
then reference should be made by color space prefix
(see
.PN XcmsFormatOfPrefix
and
.PN XcmsPrefixOfFormat ).
.LP
If the 
.PN XcmsColorSpace
structure is already accessible in the color management system, 
.PN XcmsAddColorSpace
returns 
.PN XcmsSuccess .
.LP
Note that added 
.PN XcmsColorSpaces
must be retained for reference by Xlib.
.NH 3
Querying Color Space Format and Prefix
.XS
\*(SN Querying Color Space Format and Prefix
.XE
.LP
To obtain the format associated with the color space
associated with a specified color string prefix, use
.PN XcmsFormatOfPrefix .
.IN  "XcmsFormatOfPrefix" "" "@DEF@"
.sM
.FD 0
XcmsColorFormat XcmsFormatOfPrefix\^(\^\fIprefix\fP\^)
.br
      char *\fIprefix\fP\^;
.FN
.IP \fIprefix\fP 1i
Specifies the string that contains the color space prefix.
.LP
.eM
The
.PN XcmsFormatOfPrefix
function returns the format for the specified color space prefix
(for example, the string ``CIEXYZ'').
The prefix is case-insensitive.
If the color space is not accessible in the color management system,
.PN XcmsFormatOfPrefix
returns 
.PN XcmsUndefinedFormat .
.LP
.sp
To obtain the color string prefix associated with the color space
specified by a color format, use
.PN XcmsPrefixOfFormat .
.IN  "XcmsPrefixOfFormat" "" "@DEF@"
.sM
.FD 0
char *XcmsPrefixOfFormat\^(\^\fIformat\fP\^)
.br
      XcmsColorFormat \fIformat\fP\^;
.FN
.IP \fIformat\fP 1i
Specifies the color specification format.
.LP
.eM
The
.PN XcmsPrefixOfFormat
function returns the string prefix associated with the color specification
encoding specified by the format argument.
Otherwise, if no encoding is found, it returns NULL.
The returned string must be treated as read-only.
.NH 3
Creating Additional Color Spaces
.XS
\*(SN Creating Additional Color Spaces
.XE
.LP
Color space specific information necessary 
for color space conversion and color string parsing is stored in an
.PN XcmsColorSpace
structure.
Therefore, a new structure containing this information is required
for each additional color space.
In the case of device-independent color spaces,
a handle to this new structure (that is, by means of a global variable)
is usually made accessible to the client program for use with the
.PN XcmsAddColorSpace
function.
.LP
If a new 
.PN XcmsColorSpace
structure specifies a color space not registered with the X Consortium,
they should be treated as private to the client
because format values for unregistered color spaces are assigned at run time.
If references to an unregistered color space must be made outside the
client (for example, storing color specifications in a file using the
unregistered color space), then reference should be made by color space prefix
(see
.PN XcmsFormatOfPrefix
and
.PN XcmsPrefixOfFormat ).
.sM
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef (*XcmsConversionProc)();
typedef XcmsConversionProc *XcmsFuncListPtr;
		/* A NULL terminated list of function pointers*/

typedef struct _XcmsColorSpace {
	char *prefix;
	XcmsColorFormat format;
	XcmsParseStringProc parseString;
	XcmsFuncListPtr to_CIEXYZ;
	XcmsFuncListPtr from_CIEXYZ;
	int inverse_flag;
} XcmsColorSpace;
.De
.LP
.eM
The prefix member specifies the prefix that indicates a color string 
is in this color space's string format.
For example, the strings ``ciexyz'' or ``CIEXYZ'' for CIE XYZ,
and ``rgb'' or ``RGB'' for RGB.
The prefix is case insensitive.
The format member specifies the color specification format.
Formats for unregistered color spaces are assigned at run time.
The parseString member contains a pointer to the function 
that can parse a color string into an 
.PN XcmsColor
structure.
This function returns an integer (int): nonzero if it succeeded
and zero otherwise.
The to_CIEXYZ and from_CIEXYZ members contain pointers,
each to a NULL terminated list of function pointers.
When the list of functions is executed in series,
it will convert the color specified in an 
.PN XcmsColor
structure from/to the current color space format to/from the CIE XYZ format.
Each function returns an integer (int): nonzero if it succeeded
and zero otherwise.
The white point to be associated with the colors is specified
explicitly, even though white points can be found in the CCC.
The inverse_flag member, if nonzero, specifies that for each function listed 
in to_CIEXYZ,
its inverse function can be found in from_CIEXYZ such that:
.LP
.Ds 0
Given:  n = number of functions in each list

for each i, such that 0 <= i < n
    from_CIEXYZ[n - i - 1] is the inverse of to_CIEXYZ[i].
.De
.LP
This allows Xlib to use the shortest conversion path,
thus bypassing CIE XYZ if possible (for example, TekHVC to CIE L*u*v*).
.NH 3
Parse String Callback
.XS
\*(SN Parse String Callback
.XE
.LP
The callback in the
.PN XcmsColorSpace
structure for parsing a color string for the particular color space must
adhere to the following software interface specification:
.IN  "XcmsParseStringProc" "" "@DEF@"
.sM
.FD 0
typedef int (*XcmsParseStringProc)\^(\^\fIcolor_string\fP, \fIcolor_return\fP\^)
.br
      char *\fIcolor_string\fP\^;
.br
      XcmsColor *\fIcolor_return\fP\^;
.FN
.IP \fIcolor_string\fP 1i
Specifies the color string to parse.
.IP \fIcolor_return\fP 1i
Returns the color specification in the color space's format.
.LP
.eM
.NH 3
Color Specification Conversion Callback
.XS
\*(SN Color Specification Conversion Callback
.XE
.LP
Callback functions in the
.PN XcmsColorSpace
structure for converting a color specification between device-independent
spaces must adhere to the
following software interface specification:
.sM
.FD 0
Status ConversionProc\^(\^\fIccc\fP, \fIwhite_point\fP, \fIcolors_in_out\fP, \fIncolors\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColor *\fIwhite_point\fP\^;
.br
      XcmsColor *\fIcolors_in_out\fP\^;
.br
      unsigned int \fIncolors\fP\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.IP \fIwhite_point\fP 1i
Specifies the white point associated with color specifications.
The pixel member should be ignored,
and the entire structure remain unchanged upon return.
.IP \fIcolors_in_out\fP 1i
Specifies an array of color specifications.
Pixel members should be ignored and must remain unchanged upon return.
.IP \fIncolors\fP 1i
Specifies the number of 
.PN XcmsColor
structures in the color-specification array.
.LP
.eM
.sp
Callback functions in the
.PN XcmsColorSpace
structure for converting a color specification to or from a device-dependent
space must adhere to the
following software interface specification:
.sM
.FD 0
Status ConversionProc\^(\^\fIccc\fP, \fIcolors_in_out\fP, \fIncolors\fP, \fIcompression_flags_return\fP\^)
.br
      XcmsCCC \fIccc\fP\^;
.br
      XcmsColor *\fIcolors_in_out\fP\^;
.br
      unsigned int \fIncolors\fP\^;
.br
      Bool \fIcompression_flags_return\fP\^[\^]\^;
.FN
.IP \fIccc\fP 1i
Specifies the CCC.
.IP \fIcolors_in_out\fP 1i
Specifies an array of color specifications.
Pixel members should be ignored and must remain unchanged upon return.
.IP \fIncolors\fP 1i
Specifies the number of 
.PN XcmsColor
structures in the color-specification array.
.IP \fIcompression_flags_return\fP 1i
Returns an array of Boolean values for indicating compression status.
If a non-NULL pointer is supplied
and a color at a given index is compressed, then
.PN True
should be stored at the corresponding index in this array;
otherwise, the array should not be modified.
.LP
.eM
Conversion functions are available globally for use by other color
spaces.
The conversion functions provided by Xlib are:
.TS H
lw(1.8i) lw(1.8i) lw(1.8i).
_
.sp 6p
.B
Function	Converts from	Converts to
.sp 6p
_
.sp 6p
.TH
.R
T{
.PN XcmsCIELabToCIEXYZ
T}	T{
.PN XcmsCIELabFormat
T}	T{
.PN XcmsCIEXYZFormat
T}
T{
.PN XcmsCIELuvToCIEuvY
T}	T{
.PN XcmsCIELuvFormat
T}	T{
.PN XcmsCIEuvYFormat
T}
T{
.PN XcmsCIEXYZToCIELab
T}	T{
.PN XcmsCIEXYZFormat
T}	T{
.PN XcmsCIELabFormat
T}
T{
.PN XcmsCIEXYZToCIEuvY
T}	T{
.PN XcmsCIEXYZFormat
T}	T{
.PN XcmsCIEuvYFormat
T}
T{
.PN XcmsCIEXYZToCIExyY
T}	T{
.PN XcmsCIEXYZFormat
T}	T{
.PN XcmsCIExyYFormat
T}
T{
.PN XcmsCIEXYZToRGBi
T}	T{
.PN XcmsCIEXYZFormat
T}	T{
.PN XcmsRGBiFormat
T}
T{
.PN XcmsCIEuvYToCIELuv
T}	T{
.PN XcmsCIEuvYFormat
T}	T{
.PN XcmsCIELabFormat
T}
T{
.PN XcmsCIEuvYToCIEXYZ
T}	T{
.PN XcmsCIEuvYFormat
T}	T{
.PN XcmsCIEXYZFormat
T}
T{
.PN XcmsCIEuvYToTekHVC
T}	T{
.PN XcmsCIEuvYFormat
T}	T{
.PN XcmsTekHVCFormat
T}
T{
.PN XcmsCIExyYToCIEXYZ
T}	T{
.PN XcmsCIExyYFormat
T}	T{
.PN XcmsCIEXYZFormat
T}
T{
.PN XcmsRGBToRGBi
T}	T{
.PN XcmsRGBFormat
T}	T{
.PN XcmsRGBiFormat
T}
T{
.PN XcmsRGBiToCIEXYZ
T}	T{
.PN XcmsRGBiFormat
T}	T{
.PN XcmsCIEXYZFormat
T}
T{
.PN XcmsRGBiToRGB
T}	T{
.PN XcmsRGBiFormat
T}	T{
.PN XcmsRGBFormat
T}
T{
.PN XcmsTekHVCToCIEuvY
T}	T{
.PN XcmsTekHVCFormat
T}	T{
.PN XcmsCIEuvYFormat
T}
.sp 6p
_
.TE
.NH 3
Function Sets
.XS
\*(SN Function Sets
.XE
.IN "Function set"
.IN "Function set" "LINEAR_RGB"
.LP
Functions to convert between device-dependent color spaces
and CIE XYZ may differ for different classes of output devices
(for example, color versus gray monitors).
Therefore, the notion of a Color Characterization Function Set
has been developed.
A function set consists of device-dependent color spaces
and the functions that convert color specifications 
between these device-dependent color spaces and the CIE XYZ color space
appropriate for a particular class of output devices.
The function set also contains a function that reads
color characterization data off root window properties.
It is this characterization data that will differ between devices within
a class of output devices.
.IN "Device Color Characterization"
For details about how color characterization data is
stored in root window properties,
see the section on Device Color Characterization in the
\fIInter-Client Communication Conventions Manual\fP.
The LINEAR_RGB function set is provided by Xlib
and will support most color monitors.
Function sets may require data that differs
from those needed for the LINEAR_RGB function set.
In that case, 
its corresponding data may be stored on different root window properties.
.NH 3
Adding Function Sets
.XS
\*(SN Adding Function Sets
.XE
.LP
To add a function set, use
.PN XcmsAddFunctionSet .
.IN  "XcmsAddFunctionSet" "" "@DEF@"
.sM
.FD 0
Status XcmsAddFunctionSet\^(\^\fIfunction_set\fP\^)
.br
      XcmsFunctionSet *\fIfunction_set\fP\^;
.FN
.IP \fIfunction_set\fP 1i
Specifies the function set to add.
.LP
.eM
The
.PN XcmsAddFunctionSet
function adds a function set to the color management system.
If the function set uses device-dependent 
.PN XcmsColorSpace
structures not accessible in the color management system,
.PN XcmsAddFunctionSet
adds them.
If an added
.PN XcmsColorSpace
structure is for a device-dependent color space not registered
with the X Consortium,
they should be treated as private to the client
because format values for unregistered color spaces are assigned at run time.
If references to an unregistered color space must be made outside the
client (for example, storing color specifications in a file
using the unregistered color space),
then reference should be made by color space prefix
(see 
.PN XcmsFormatOfPrefix
and
.PN XcmsPrefixOfFormat ).
.LP
Additional function sets should be added before any calls to other
Xlib routines are made.
If not, the 
.PN XcmsPerScrnInfo
member of a previously created 
.PN XcmsCCC
does not have the opportunity to initialize
with the added function set.
.NH 3
Creating Additional Function Sets
.XS
\*(SN Creating Additional Function Sets
.XE
.LP
The creation of additional function sets should be
required only when an output device does not conform to existing 
function sets or when additional device-dependent color spaces are necessary.
A function set consists primarily of a collection of device-dependent
.PN XcmsColorSpace
structures and a means to read and store a 
screen's color characterization data.
This data is stored in an
.PN XcmsFunctionSet
structure.
A handle to this structure (that is, by means of global variable)
is usually made accessible to the client program for use with
.PN XcmsAddFunctionSet .
.LP
If a function set uses new device-dependent 
.PN XcmsColorSpace
structures,
they will be transparently processed into the color management system.
Function sets can share an 
.PN XcmsColorSpace
structure for a device-dependent color space.
In addition, multiple 
.PN XcmsColorSpace
structures are allowed for a device-dependent color space;
however, a function set can reference only one of them.
These 
.PN XcmsColorSpace
structures will differ in the functions to convert to and from CIE XYZ,
thus tailored for the specific function set.
.sM
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct _XcmsFunctionSet {
	XcmsColorSpace **DDColorSpaces;
	XcmsScreenInitProc screenInitProc;
	XcmsScreenFreeProc screenFreeProc;
} XcmsFunctionSet;
.De
.LP
.eM
The DDColorSpaces member is a pointer to a NULL terminated list
of pointers to 
.PN XcmsColorSpace
structures for the device-dependent color spaces that are supported
by the function set.
The screenInitProc member is set to the callback procedure (see the following
interface specification) that initializes the 
.PN XcmsPerScrnInfo
structure for a particular screen.
.LP
The screen initialization callback must adhere to the following software
interface specification:
.IN  "XcmsScreenInitProc" "" "@DEF@"
.sM
.FD 0
typedef Status (*XcmsScreenInitProc)\^(\^\fIdisplay\fP, \fIscreen_number\fP, \fIscreen_info\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      int \fIscreen_number\fP\^;
.br
      XcmsPerScrnInfo *\fIscreen_info\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIscreen_number\fP 1i
Specifies the appropriate screen number on the host server.
.IP \fIscreen_info\fP 1i
Specifies the 
.PN XcmsPerScrnInfo 
structure, which contains the per screen information.
.LP
.eM
The screen initialization callback in the
.PN XcmsFunctionSet
structure fetches the color characterization data (device profile) for
the specified screen,
typically off properties on the 
screen's root window.
It then initializes the specified
.PN XcmsPerScrnInfo
structure.
.IN "Device profile"
.IN "Color Characterization Data"
If successful, the procedure fills in the 
.PN XcmsPerScrnInfo
structure as follows:
.IP \(bu 5
It sets the screenData member to the address 
of the created device profile data structure 
(contents known only by the function set).
.IP \(bu 5
It next sets the screenWhitePoint member.
.IP \(bu 5
It next sets the functionSet member to the address of the
.PN XcmsFunctionSet
structure.
.IP \(bu 5
It then sets the state member to 
.PN XcmsInitSuccess 
and finally returns
.PN XcmsSuccess .
.LP
If unsuccessful, the procedure sets the state member to 
.PN XcmsInitFailure
and returns
.PN XcmsFailure .
.LP
The
.PN XcmsPerScrnInfo
structure contains:
.sM
.LP
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
typedef struct _XcmsPerScrnInfo {
	XcmsColor screenWhitePoint;
	XPointer functionSet;
	XPointer screenData;
	unsigned char state;
	char pad[3];
} XcmsPerScrnInfo;
.De
.LP
.eM
The screenWhitePoint member specifies the white point inherent to
the screen.
The functionSet member specifies the appropriate function set.
The screenData member specifies the device profile.
The state member is set to one of the following:
.IP \(bu 5
.PN XcmsInitNone
indicates initialization has not been previously attempted.
.IP \(bu 5
.PN XcmsInitFailure
indicates initialization has been previously attempted but failed.
.IP \(bu 5
.PN XcmsInitSuccess
indicates initialization has been previously attempted and succeeded.
.LP
The screen free callback must adhere to the following software
interface specification:
.IN  "XcmsScreenFreeProc" "" "@DEF@"
.sM
.FD 0
typedef void (*XcmsScreenFreeProc)\^(\^\fIscreenData\fP\^)
.br
      XPointer \fIscreenData\fP\^;
.FN
.IP \fIscreenData\fP 1i
Specifies the data to be freed.
.LP
.eM
This function is called to free the screenData stored in an
.PN XcmsPerScrnInfo
structure.
.bp