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png: Update for Go 1.12
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Hajime Hoshi
parent
c5a8c88e2d
commit
e5b1aa8742
@ -9,6 +9,7 @@ package png
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import (
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"bufio"
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"compress/zlib"
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"encoding/binary"
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"hash/crc32"
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"image"
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"image/color"
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@ -64,14 +65,6 @@ const (
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// compression level, although that is not implemented yet.
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)
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// Big-endian.
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func writeUint32(b []uint8, u uint32) {
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b[0] = uint8(u >> 24)
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b[1] = uint8(u >> 16)
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b[2] = uint8(u >> 8)
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b[3] = uint8(u >> 0)
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}
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type opaquer interface {
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Opaque() bool
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}
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@ -110,7 +103,7 @@ func (e *encoder) writeChunk(b []byte, name string) {
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e.err = UnsupportedError(name + " chunk is too large: " + strconv.Itoa(len(b)))
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return
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}
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writeUint32(e.header[:4], n)
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binary.BigEndian.PutUint32(e.header[:4], n)
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e.header[4] = name[0]
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e.header[5] = name[1]
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e.header[6] = name[2]
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@ -118,7 +111,7 @@ func (e *encoder) writeChunk(b []byte, name string) {
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crc := crc32.NewIEEE()
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crc.Write(e.header[4:8])
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crc.Write(b)
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writeUint32(e.footer[:4], crc.Sum32())
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binary.BigEndian.PutUint32(e.footer[:4], crc.Sum32())
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_, e.err = e.w.Write(e.header[:8])
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if e.err != nil {
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@ -133,8 +126,8 @@ func (e *encoder) writeChunk(b []byte, name string) {
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func (e *encoder) writeIHDR() {
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b := e.m.Bounds()
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writeUint32(e.tmp[0:4], uint32(b.Dx()))
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writeUint32(e.tmp[4:8], uint32(b.Dy()))
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binary.BigEndian.PutUint32(e.tmp[0:4], uint32(b.Dx()))
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binary.BigEndian.PutUint32(e.tmp[4:8], uint32(b.Dy()))
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// Set bit depth and color type.
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switch e.cb {
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case cbG8:
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@ -146,6 +139,15 @@ func (e *encoder) writeIHDR() {
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case cbP8:
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e.tmp[8] = 8
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e.tmp[9] = ctPaletted
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case cbP4:
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e.tmp[8] = 4
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e.tmp[9] = ctPaletted
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case cbP2:
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e.tmp[8] = 2
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e.tmp[9] = ctPaletted
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case cbP1:
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e.tmp[8] = 1
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e.tmp[9] = ctPaletted
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case cbTCA8:
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e.tmp[8] = 8
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e.tmp[9] = ctTrueColorAlpha
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@ -314,31 +316,38 @@ func (e *encoder) writeImage(w io.Writer, m image.Image, cb int, level int) erro
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}
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defer e.zw.Close()
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bpp := 0 // Bytes per pixel.
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bitsPerPixel := 0
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switch cb {
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case cbG8:
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bpp = 1
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bitsPerPixel = 8
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case cbTC8:
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bpp = 3
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bitsPerPixel = 24
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case cbP8:
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bpp = 1
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bitsPerPixel = 8
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case cbP4:
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bitsPerPixel = 4
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case cbP2:
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bitsPerPixel = 2
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case cbP1:
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bitsPerPixel = 1
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case cbTCA8:
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bpp = 4
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bitsPerPixel = 32
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case cbTC16:
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bpp = 6
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bitsPerPixel = 48
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case cbTCA16:
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bpp = 8
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bitsPerPixel = 64
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case cbG16:
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bpp = 2
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bitsPerPixel = 16
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}
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// cr[*] and pr are the bytes for the current and previous row.
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// cr[0] is unfiltered (or equivalently, filtered with the ftNone filter).
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// cr[ft], for non-zero filter types ft, are buffers for transforming cr[0] under the
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// other PNG filter types. These buffers are allocated once and re-used for each row.
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// The +1 is for the per-row filter type, which is at cr[*][0].
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b := m.Bounds()
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sz := 1 + bpp*b.Dx()
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sz := 1 + (bitsPerPixel*b.Dx()+7)/8
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for i := range e.cr {
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if cap(e.cr[i]) < sz {
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e.cr[i] = make([]uint8, sz)
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@ -414,6 +423,30 @@ func (e *encoder) writeImage(w io.Writer, m image.Image, cb int, level int) erro
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i += 1
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}
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}
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case cbP4, cbP2, cbP1:
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pi := m.(image.PalettedImage)
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var a uint8
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var c int
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for x := b.Min.X; x < b.Max.X; x++ {
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a = a<<uint(bitsPerPixel) | pi.ColorIndexAt(x, y)
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c++
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if c == 8/bitsPerPixel {
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cr[0][i] = a
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i += 1
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a = 0
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c = 0
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}
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}
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if c != 0 {
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for c != 8/bitsPerPixel {
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a = a << uint(bitsPerPixel)
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c++
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}
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cr[0][i] = a
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}
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case cbTCA8:
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if nrgba != nil {
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offset := (y - b.Min.Y) * nrgba.Stride
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@ -469,7 +502,10 @@ func (e *encoder) writeImage(w io.Writer, m image.Image, cb int, level int) erro
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// "filters are rarely useful on palette images" and will result
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// in larger files (see http://www.libpng.org/pub/png/book/chapter09.html).
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f := ftNone
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if level != zlib.NoCompression && cb != cbP8 {
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if level != zlib.NoCompression && cb != cbP8 && cb != cbP4 && cb != cbP2 && cb != cbP1 {
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// Since we skip paletted images we don't have to worry about
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// bitsPerPixel not being a multiple of 8
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bpp := bitsPerPixel / 8
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f = filter(&cr, pr, bpp)
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}
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@ -560,7 +596,15 @@ func (enc *Encoder) Encode(w io.Writer, m image.Image) error {
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pal, _ = m.ColorModel().(color.Palette)
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}
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if pal != nil {
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e.cb = cbP8
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if len(pal) <= 2 {
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e.cb = cbP1
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} else if len(pal) <= 4 {
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e.cb = cbP2
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} else if len(pal) <= 16 {
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e.cb = cbP4
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} else {
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e.cb = cbP8
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}
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} else {
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switch m.ColorModel() {
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case color.GrayModel:
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