summaryrefslogtreecommitdiff
path: root/src/pkg/image/png/writer.go
diff options
context:
space:
mode:
Diffstat (limited to 'src/pkg/image/png/writer.go')
-rw-r--r--src/pkg/image/png/writer.go98
1 files changed, 58 insertions, 40 deletions
diff --git a/src/pkg/image/png/writer.go b/src/pkg/image/png/writer.go
index 2d593f6a7..d770cfad5 100644
--- a/src/pkg/image/png/writer.go
+++ b/src/pkg/image/png/writer.go
@@ -130,12 +130,8 @@ func (e *encoder) writePLTE(p image.PalettedColorModel) {
e.err = FormatError("bad palette length: " + strconv.Itoa(len(p)))
return
}
- for i := 0; i < len(p); i++ {
- r, g, b, a := p[i].RGBA()
- if a != 0xffff {
- e.err = UnsupportedError("non-opaque palette color")
- return
- }
+ for i, c := range p {
+ r, g, b, _ := c.RGBA()
e.tmp[3*i+0] = uint8(r >> 8)
e.tmp[3*i+1] = uint8(g >> 8)
e.tmp[3*i+2] = uint8(b >> 8)
@@ -143,6 +139,21 @@ func (e *encoder) writePLTE(p image.PalettedColorModel) {
e.writeChunk(e.tmp[0:3*len(p)], "PLTE")
}
+func (e *encoder) maybeWritetRNS(p image.PalettedColorModel) {
+ last := -1
+ for i, c := range p {
+ _, _, _, a := c.RGBA()
+ if a != 0xffff {
+ last = i
+ }
+ e.tmp[i] = uint8(a >> 8)
+ }
+ if last == -1 {
+ return
+ }
+ e.writeChunk(e.tmp[:last+1], "tRNS")
+}
+
// An encoder is an io.Writer that satisfies writes by writing PNG IDAT chunks,
// including an 8-byte header and 4-byte CRC checksum per Write call. Such calls
// should be relatively infrequent, since writeIDATs uses a bufio.Writer.
@@ -163,7 +174,7 @@ func (e *encoder) Write(b []byte) (int, os.Error) {
// Chooses the filter to use for encoding the current row, and applies it.
// The return value is the index of the filter and also of the row in cr that has had it applied.
-func filter(cr [][]byte, pr []byte, bpp int) int {
+func filter(cr *[nFilter][]byte, pr []byte, bpp int) int {
// We try all five filter types, and pick the one that minimizes the sum of absolute differences.
// This is the same heuristic that libpng uses, although the filters are attempted in order of
// estimated most likely to be minimal (ftUp, ftPaeth, ftNone, ftSub, ftAverage), rather than
@@ -293,7 +304,7 @@ func writeImage(w io.Writer, m image.Image, cb int) os.Error {
// The +1 is for the per-row filter type, which is at cr[*][0].
b := m.Bounds()
var cr [nFilter][]uint8
- for i := 0; i < len(cr); i++ {
+ for i := range cr {
cr[i] = make([]uint8, 1+bpp*b.Dx())
cr[i][0] = uint8(i)
}
@@ -301,78 +312,84 @@ func writeImage(w io.Writer, m image.Image, cb int) os.Error {
for y := b.Min.Y; y < b.Max.Y; y++ {
// Convert from colors to bytes.
+ i := 1
switch cb {
case cbG8:
for x := b.Min.X; x < b.Max.X; x++ {
c := image.GrayColorModel.Convert(m.At(x, y)).(image.GrayColor)
- cr[0][x+1] = c.Y
+ cr[0][i] = c.Y
+ i++
}
case cbTC8:
// We have previously verified that the alpha value is fully opaque.
cr0 := cr[0]
if rgba != nil {
yoff := y * rgba.Stride
- xoff := 3*b.Min.X + 1
for _, color := range rgba.Pix[yoff+b.Min.X : yoff+b.Max.X] {
- cr0[xoff] = color.R
- cr0[xoff+1] = color.G
- cr0[xoff+2] = color.B
- xoff += 3
+ cr0[i+0] = color.R
+ cr0[i+1] = color.G
+ cr0[i+2] = color.B
+ i += 3
}
} else {
for x := b.Min.X; x < b.Max.X; x++ {
r, g, b, _ := m.At(x, y).RGBA()
- cr0[3*x+1] = uint8(r >> 8)
- cr0[3*x+2] = uint8(g >> 8)
- cr0[3*x+3] = uint8(b >> 8)
+ cr0[i+0] = uint8(r >> 8)
+ cr0[i+1] = uint8(g >> 8)
+ cr0[i+2] = uint8(b >> 8)
+ i += 3
}
}
case cbP8:
rowOffset := y * paletted.Stride
- copy(cr[0][b.Min.X+1:], paletted.Pix[rowOffset+b.Min.X:rowOffset+b.Max.X])
+ copy(cr[0][1:], paletted.Pix[rowOffset+b.Min.X:rowOffset+b.Max.X])
case cbTCA8:
// Convert from image.Image (which is alpha-premultiplied) to PNG's non-alpha-premultiplied.
for x := b.Min.X; x < b.Max.X; x++ {
c := image.NRGBAColorModel.Convert(m.At(x, y)).(image.NRGBAColor)
- cr[0][4*x+1] = c.R
- cr[0][4*x+2] = c.G
- cr[0][4*x+3] = c.B
- cr[0][4*x+4] = c.A
+ cr[0][i+0] = c.R
+ cr[0][i+1] = c.G
+ cr[0][i+2] = c.B
+ cr[0][i+3] = c.A
+ i += 4
}
case cbG16:
for x := b.Min.X; x < b.Max.X; x++ {
c := image.Gray16ColorModel.Convert(m.At(x, y)).(image.Gray16Color)
- cr[0][2*x+1] = uint8(c.Y >> 8)
- cr[0][2*x+2] = uint8(c.Y)
+ cr[0][i+0] = uint8(c.Y >> 8)
+ cr[0][i+1] = uint8(c.Y)
+ i += 2
}
case cbTC16:
+ // We have previously verified that the alpha value is fully opaque.
for x := b.Min.X; x < b.Max.X; x++ {
- // We have previously verified that the alpha value is fully opaque.
r, g, b, _ := m.At(x, y).RGBA()
- cr[0][6*x+1] = uint8(r >> 8)
- cr[0][6*x+2] = uint8(r)
- cr[0][6*x+3] = uint8(g >> 8)
- cr[0][6*x+4] = uint8(g)
- cr[0][6*x+5] = uint8(b >> 8)
- cr[0][6*x+6] = uint8(b)
+ cr[0][i+0] = uint8(r >> 8)
+ cr[0][i+1] = uint8(r)
+ cr[0][i+2] = uint8(g >> 8)
+ cr[0][i+3] = uint8(g)
+ cr[0][i+4] = uint8(b >> 8)
+ cr[0][i+5] = uint8(b)
+ i += 6
}
case cbTCA16:
// Convert from image.Image (which is alpha-premultiplied) to PNG's non-alpha-premultiplied.
for x := b.Min.X; x < b.Max.X; x++ {
c := image.NRGBA64ColorModel.Convert(m.At(x, y)).(image.NRGBA64Color)
- cr[0][8*x+1] = uint8(c.R >> 8)
- cr[0][8*x+2] = uint8(c.R)
- cr[0][8*x+3] = uint8(c.G >> 8)
- cr[0][8*x+4] = uint8(c.G)
- cr[0][8*x+5] = uint8(c.B >> 8)
- cr[0][8*x+6] = uint8(c.B)
- cr[0][8*x+7] = uint8(c.A >> 8)
- cr[0][8*x+8] = uint8(c.A)
+ cr[0][i+0] = uint8(c.R >> 8)
+ cr[0][i+1] = uint8(c.R)
+ cr[0][i+2] = uint8(c.G >> 8)
+ cr[0][i+3] = uint8(c.G)
+ cr[0][i+4] = uint8(c.B >> 8)
+ cr[0][i+5] = uint8(c.B)
+ cr[0][i+6] = uint8(c.A >> 8)
+ cr[0][i+7] = uint8(c.A)
+ i += 8
}
}
// Apply the filter.
- f := filter(cr[0:nFilter], pr, bpp)
+ f := filter(&cr, pr, bpp)
// Write the compressed bytes.
_, err = zw.Write(cr[f])
@@ -447,6 +464,7 @@ func Encode(w io.Writer, m image.Image) os.Error {
e.writeIHDR()
if pal != nil {
e.writePLTE(pal.Palette)
+ e.maybeWritetRNS(pal.Palette)
}
e.writeIDATs()
e.writeIEND()
generated by cgit v1.2.3 (git 2.39.1) at 2025-04-28 05:47:39 +0000