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image/gif: respect local color table transparency.

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Fixes #6441.

R=r
CC=andybons, golang-dev
https://golang.org/cl/13829043
This commit is contained in:
Nigel Tao 2013-12-18 15:10:40 -05:00 committed by Russ Cox
parent 9607255760
commit ff6b922361
1 changed files with 11 additions and 11 deletions
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22
src/pkg/image/gif/reader.go
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@ -79,7 +79,8 @@ type decoder struct {
imageFields byte
// From graphics control.
transparentIndex byte
transparentIndex byte
hasTransparentIndex bool
// Computed.
pixelSize uint
@ -175,11 +176,12 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error {
if err != nil {
return err
}
// TODO: do we set transparency in this map too? That would be
// d.setTransparency(m.Palette)
} else {
m.Palette = d.globalColorMap
}
if d.hasTransparentIndex && int(d.transparentIndex) < len(m.Palette) {
m.Palette[d.transparentIndex] = color.RGBA{}
}
litWidth, err := d.r.ReadByte()
if err != nil {
return err
@ -228,7 +230,11 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error {
d.image = append(d.image, m)
d.delay = append(d.delay, d.delayTime)
d.delayTime = 0 // TODO: is this correct, or should we hold on to the value?
// The GIF89a spec, Section 23 (Graphic Control Extension) says:
// "The scope of this extension is the first graphic rendering block
// to follow." We therefore reset the GCE fields to zero.
d.delayTime = 0
d.hasTransparentIndex = false
case sTrailer:
if len(d.image) == 0 {
@ -339,17 +345,11 @@ func (d *decoder) readGraphicControl() error {
d.delayTime = int(d.tmp[2]) | int(d.tmp[3])<<8
if d.flags&gcTransparentColorSet != 0 {
d.transparentIndex = d.tmp[4]
d.setTransparency(d.globalColorMap)
d.hasTransparentIndex = true
}
return nil
}
func (d *decoder) setTransparency(colorMap color.Palette) {
if int(d.transparentIndex) < len(colorMap) {
colorMap[d.transparentIndex] = color.RGBA{}
}
}
func (d *decoder) newImageFromDescriptor() (*image.Paletted, error) {
if _, err := io.ReadFull(d.r, d.tmp[0:9]); err != nil {
return nil, fmt.Errorf("gif: can't read image descriptor: %s", err)