139 lines
3.6 KiB
RPMSpec
139 lines
3.6 KiB
RPMSpec
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Name
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MESA_pack_invert
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Name Strings
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GL_MESA_pack_invert
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Contact
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Brian Paul, Tungsten Graphics, Inc. (brian.paul 'at' tungstengraphics.com)
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Keith Whitwell, Tungsten Graphics, Inc. (keith 'at' tungstengraphics.com)
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Status
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Shipping (Mesa 4.0.4 and later)
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Version
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1.0
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Number
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TBD
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Dependencies
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OpenGL 1.0 or later is required
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This extensions is written against the OpenGL 1.4 Specification.
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Overview
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This extension adds a new pixel storage parameter to indicate that
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images are to be packed in top-to-bottom order instead of OpenGL's
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conventional bottom-to-top order. Only pixel packing can be
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inverted (i.e. for glReadPixels, glGetTexImage, glGetConvolutionFilter,
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etc).
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Almost all known image file formats store images in top-to-bottom
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order. As it is, OpenGL reads images from the frame buffer in
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bottom-to-top order. Thus, images usually have to be inverted before
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writing them to a file with image I/O libraries. This extension
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allows images to be read such that inverting isn't needed.
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IP Status
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None
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Issues
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1. Should we also defined UNPACK_INVERT_MESA for glDrawPixels, etc?
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Resolved: No, we're only concerned with pixel packing. There are other
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solutions for inverting images when using glDrawPixels (negative Y pixel
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zoom) or glTexImage (invert the vertex T coordinates). It would be easy
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enough to define a complementary extension for pixel packing in the
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future if needed.
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New Procedures and Functions
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None
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New Tokens
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Accepted by the <pname> parameter of PixelStorei and PixelStoref
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and the <pname> parameter of GetIntegerv, GetFloatv, GetDoublev
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and GetBooleanv:
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PACK_INVERT_MESA 0x8758
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Additions to Chapter 2 of the OpenGL 1.4 Specification (OpenGL Operation)
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None
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Additions to Chapter 3 of the OpenGL 1.4 Specification (Rasterization)
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None
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Additions to Chapter 4 of the OpenGL 1.4 Specification (Per-Fragment
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Operations and the Frame Buffer)
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Add the following entry to table 4.4 (PixelStore parameters) on page 182:
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Parameter Name Type Initial Value Valid Range
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---------------------------------------------------------
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PACK_INVERT_MESA boolean FALSE TRUE/FALSE
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In the section labeled "Placement in Client Memory" on page 184
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insert the following text into the paragraph before the sentence
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that starts with "If the format is RED, GREEN, BLUE...":
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"The parameter PACK_INVERT_MESA controls whether the image is packed
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in bottom-to-top order (the default) or top-to-bottom order. Equation
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3.8 is modified as follows:
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... the first element of the Nth row is indicated by
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p + Nk, if PACK_INVERT_MESA is false
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p + k * (H - 1) - Nk, if PACK_INVERT_MESA is true, where H is the
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image height
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"
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Additions to Chapter 5 of the OpenGL 1.4 Specification (Special Functions)
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None
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Additions to Chapter 6 of the OpenGL 1.4 Specification (State and
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State Requests)
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None
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Additions to Appendix A of the OpenGL 1.4 Specification (Invariance)
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None
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Additions to the AGL/GLX/WGL Specifications
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None
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GLX Protocol
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None
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Errors
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None
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New State
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Add the following entry to table 6.20 (Pixels) on page 235:
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Get Value Type Get Cmd Initial Value Description Sec Attribute
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--------------------------------------------------------------------------------------------------
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PACK_INVERT_MESA boolean GetBoolean FALSE Value of PACK_INVERT_MESA 4.3.2 pixel-store
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Revision History
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21 September 2002 - Initial draft
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