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PNG decoder now handles transparent paletted images.

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Fixes #439.

R=r
CC=golang-dev
https://golang.org/cl/181087
This commit is contained in:
Nigel Tao 2009-12-29 15:23:55 +11:00
parent 50d3447a36
commit 5042a4e9f9
1 changed files with 32 additions and 0 deletions
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32
src/pkg/image/png/reader.go
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@ -164,6 +164,33 @@ func (d *decoder) parsePLTE(r io.Reader, crc hash.Hash32, length uint32) os.Erro
return nil
}
func (d *decoder) parsetRNS(r io.Reader, crc hash.Hash32, length uint32) os.Error {
if length > 256 {
return FormatError("bad tRNS length")
}
n, err := io.ReadFull(r, d.tmp[0:length])
if err != nil {
return err
}
crc.Write(d.tmp[0:n])
switch d.colorType {
case ctTrueColor:
return UnsupportedError("TrueColor transparency")
case ctPaletted:
p := d.image.(*image.Paletted).Palette
if n > len(p) {
return FormatError("bad tRNS length")
}
for i := 0; i < n; i++ {
rgba := p[i].(image.RGBAColor)
p[i] = image.RGBAColor{rgba.R, rgba.G, rgba.B, d.tmp[i]}
}
case ctTrueColorAlpha:
return FormatError("tRNS, color type mismatch")
}
return nil
}
// The Paeth filter function, as per the PNG specification.
func paeth(a, b, c uint8) uint8 {
p := int(a) + int(b) - int(c)
@ -353,6 +380,11 @@ func (d *decoder) parseChunk(r io.Reader) os.Error {
}
d.stage = dsSeenPLTE
err = d.parsePLTE(r, crc, length)
case "tRNS":
if d.stage != dsSeenPLTE {
return chunkOrderError
}
err = d.parsetRNS(r, crc, length)
case "IDAT":
if d.stage < dsSeenIHDR || d.stage > dsSeenIDAT || (d.colorType == ctPaletted && d.stage == dsSeenIHDR) {
return chunkOrderError