c2047754c3
Compiler changes:
* Change map assignment to use mapassign and assign value directly.
* Change string iteration to use decoderune, faster for ASCII strings.
* Change makeslice to take int, and use makeslice64 for larger values.
* Add new noverflow field to hmap struct used for maps.
Unresolved problems, to be fixed later:
* Commented out test in go/types/sizes_test.go that doesn't compile.
* Commented out reflect.TestStructOf test for padding after zero-sized field.
Reviewed-on: https://go-review.googlesource.com/35231
gotools/:
Updates for Go 1.8rc1.
* Makefile.am (go_cmd_go_files): Add bug.go.
(s-zdefaultcc): Write defaultPkgConfig.
* Makefile.in: Rebuild.
From-SVN: r244456
534 lines
12 KiB
Go
534 lines
12 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package png
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import (
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"bufio"
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"compress/zlib"
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"hash/crc32"
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"image"
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"image/color"
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"io"
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"strconv"
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)
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// Encoder configures encoding PNG images.
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type Encoder struct {
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CompressionLevel CompressionLevel
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}
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type encoder struct {
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enc *Encoder
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w io.Writer
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m image.Image
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cb int
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err error
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header [8]byte
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footer [4]byte
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tmp [4 * 256]byte
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}
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type CompressionLevel int
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const (
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DefaultCompression CompressionLevel = 0
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NoCompression CompressionLevel = -1
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BestSpeed CompressionLevel = -2
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BestCompression CompressionLevel = -3
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// Positive CompressionLevel values are reserved to mean a numeric zlib
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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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// Returns whether or not the image is fully opaque.
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func opaque(m image.Image) bool {
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if o, ok := m.(opaquer); ok {
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return o.Opaque()
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}
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b := m.Bounds()
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for y := b.Min.Y; y < b.Max.Y; y++ {
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for x := b.Min.X; x < b.Max.X; x++ {
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_, _, _, a := m.At(x, y).RGBA()
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if a != 0xffff {
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return false
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}
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}
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}
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return true
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}
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// The absolute value of a byte interpreted as a signed int8.
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func abs8(d uint8) int {
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if d < 128 {
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return int(d)
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}
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return 256 - int(d)
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}
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func (e *encoder) writeChunk(b []byte, name string) {
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if e.err != nil {
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return
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}
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n := uint32(len(b))
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if int(n) != len(b) {
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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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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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e.header[7] = name[3]
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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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_, e.err = e.w.Write(e.header[:8])
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if e.err != nil {
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return
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}
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_, e.err = e.w.Write(b)
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if e.err != nil {
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return
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}
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_, e.err = e.w.Write(e.footer[:4])
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}
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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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// Set bit depth and color type.
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switch e.cb {
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case cbG8:
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e.tmp[8] = 8
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e.tmp[9] = ctGrayscale
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case cbTC8:
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e.tmp[8] = 8
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e.tmp[9] = ctTrueColor
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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 cbTCA8:
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e.tmp[8] = 8
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e.tmp[9] = ctTrueColorAlpha
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case cbG16:
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e.tmp[8] = 16
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e.tmp[9] = ctGrayscale
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case cbTC16:
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e.tmp[8] = 16
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e.tmp[9] = ctTrueColor
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case cbTCA16:
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e.tmp[8] = 16
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e.tmp[9] = ctTrueColorAlpha
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}
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e.tmp[10] = 0 // default compression method
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e.tmp[11] = 0 // default filter method
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e.tmp[12] = 0 // non-interlaced
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e.writeChunk(e.tmp[:13], "IHDR")
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}
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func (e *encoder) writePLTEAndTRNS(p color.Palette) {
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if len(p) < 1 || len(p) > 256 {
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e.err = FormatError("bad palette length: " + strconv.Itoa(len(p)))
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return
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}
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last := -1
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for i, c := range p {
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c1 := color.NRGBAModel.Convert(c).(color.NRGBA)
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e.tmp[3*i+0] = c1.R
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e.tmp[3*i+1] = c1.G
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e.tmp[3*i+2] = c1.B
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if c1.A != 0xff {
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last = i
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}
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e.tmp[3*256+i] = c1.A
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}
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e.writeChunk(e.tmp[:3*len(p)], "PLTE")
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if last != -1 {
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e.writeChunk(e.tmp[3*256:3*256+1+last], "tRNS")
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}
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}
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// An encoder is an io.Writer that satisfies writes by writing PNG IDAT chunks,
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// including an 8-byte header and 4-byte CRC checksum per Write call. Such calls
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// should be relatively infrequent, since writeIDATs uses a bufio.Writer.
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//
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// This method should only be called from writeIDATs (via writeImage).
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// No other code should treat an encoder as an io.Writer.
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func (e *encoder) Write(b []byte) (int, error) {
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e.writeChunk(b, "IDAT")
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if e.err != nil {
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return 0, e.err
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}
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return len(b), nil
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}
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// Chooses the filter to use for encoding the current row, and applies it.
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// The return value is the index of the filter and also of the row in cr that has had it applied.
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func filter(cr *[nFilter][]byte, pr []byte, bpp int) int {
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// We try all five filter types, and pick the one that minimizes the sum of absolute differences.
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// This is the same heuristic that libpng uses, although the filters are attempted in order of
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// estimated most likely to be minimal (ftUp, ftPaeth, ftNone, ftSub, ftAverage), rather than
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// in their enumeration order (ftNone, ftSub, ftUp, ftAverage, ftPaeth).
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cdat0 := cr[0][1:]
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cdat1 := cr[1][1:]
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cdat2 := cr[2][1:]
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cdat3 := cr[3][1:]
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cdat4 := cr[4][1:]
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pdat := pr[1:]
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n := len(cdat0)
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// The up filter.
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sum := 0
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for i := 0; i < n; i++ {
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cdat2[i] = cdat0[i] - pdat[i]
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sum += abs8(cdat2[i])
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}
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best := sum
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filter := ftUp
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// The Paeth filter.
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sum = 0
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for i := 0; i < bpp; i++ {
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cdat4[i] = cdat0[i] - pdat[i]
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sum += abs8(cdat4[i])
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}
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for i := bpp; i < n; i++ {
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cdat4[i] = cdat0[i] - paeth(cdat0[i-bpp], pdat[i], pdat[i-bpp])
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sum += abs8(cdat4[i])
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if sum >= best {
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break
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}
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}
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if sum < best {
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best = sum
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filter = ftPaeth
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}
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// The none filter.
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sum = 0
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for i := 0; i < n; i++ {
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sum += abs8(cdat0[i])
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if sum >= best {
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break
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}
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}
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if sum < best {
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best = sum
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filter = ftNone
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}
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// The sub filter.
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sum = 0
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for i := 0; i < bpp; i++ {
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cdat1[i] = cdat0[i]
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sum += abs8(cdat1[i])
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}
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for i := bpp; i < n; i++ {
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cdat1[i] = cdat0[i] - cdat0[i-bpp]
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sum += abs8(cdat1[i])
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if sum >= best {
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break
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}
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}
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if sum < best {
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best = sum
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filter = ftSub
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}
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// The average filter.
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sum = 0
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for i := 0; i < bpp; i++ {
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cdat3[i] = cdat0[i] - pdat[i]/2
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sum += abs8(cdat3[i])
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}
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for i := bpp; i < n; i++ {
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cdat3[i] = cdat0[i] - uint8((int(cdat0[i-bpp])+int(pdat[i]))/2)
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sum += abs8(cdat3[i])
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if sum >= best {
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break
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}
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}
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if sum < best {
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best = sum
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filter = ftAverage
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}
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return filter
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}
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func writeImage(w io.Writer, m image.Image, cb int, level int) error {
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zw, err := zlib.NewWriterLevel(w, level)
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if err != nil {
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return err
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}
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defer zw.Close()
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bpp := 0 // Bytes per pixel.
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switch cb {
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case cbG8:
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bpp = 1
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case cbTC8:
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bpp = 3
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case cbP8:
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bpp = 1
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case cbTCA8:
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bpp = 4
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case cbTC16:
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bpp = 6
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case cbTCA16:
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bpp = 8
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case cbG16:
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bpp = 2
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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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var cr [nFilter][]uint8
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for i := range cr {
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cr[i] = make([]uint8, 1+bpp*b.Dx())
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cr[i][0] = uint8(i)
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}
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pr := make([]uint8, 1+bpp*b.Dx())
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gray, _ := m.(*image.Gray)
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rgba, _ := m.(*image.RGBA)
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paletted, _ := m.(*image.Paletted)
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nrgba, _ := m.(*image.NRGBA)
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for y := b.Min.Y; y < b.Max.Y; y++ {
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// Convert from colors to bytes.
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i := 1
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switch cb {
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case cbG8:
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if gray != nil {
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offset := (y - b.Min.Y) * gray.Stride
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copy(cr[0][1:], gray.Pix[offset:offset+b.Dx()])
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} else {
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for x := b.Min.X; x < b.Max.X; x++ {
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c := color.GrayModel.Convert(m.At(x, y)).(color.Gray)
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cr[0][i] = c.Y
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i++
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}
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}
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case cbTC8:
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// We have previously verified that the alpha value is fully opaque.
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cr0 := cr[0]
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stride, pix := 0, []byte(nil)
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if rgba != nil {
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stride, pix = rgba.Stride, rgba.Pix
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} else if nrgba != nil {
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stride, pix = nrgba.Stride, nrgba.Pix
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}
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if stride != 0 {
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j0 := (y - b.Min.Y) * stride
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j1 := j0 + b.Dx()*4
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for j := j0; j < j1; j += 4 {
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cr0[i+0] = pix[j+0]
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cr0[i+1] = pix[j+1]
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cr0[i+2] = pix[j+2]
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i += 3
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}
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} else {
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for x := b.Min.X; x < b.Max.X; x++ {
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r, g, b, _ := m.At(x, y).RGBA()
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cr0[i+0] = uint8(r >> 8)
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cr0[i+1] = uint8(g >> 8)
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cr0[i+2] = uint8(b >> 8)
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i += 3
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}
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}
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case cbP8:
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if paletted != nil {
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offset := (y - b.Min.Y) * paletted.Stride
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copy(cr[0][1:], paletted.Pix[offset:offset+b.Dx()])
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} else {
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pi := m.(image.PalettedImage)
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for x := b.Min.X; x < b.Max.X; x++ {
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cr[0][i] = pi.ColorIndexAt(x, y)
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i += 1
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}
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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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copy(cr[0][1:], nrgba.Pix[offset:offset+b.Dx()*4])
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} else {
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// Convert from image.Image (which is alpha-premultiplied) to PNG's non-alpha-premultiplied.
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for x := b.Min.X; x < b.Max.X; x++ {
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c := color.NRGBAModel.Convert(m.At(x, y)).(color.NRGBA)
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cr[0][i+0] = c.R
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cr[0][i+1] = c.G
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cr[0][i+2] = c.B
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cr[0][i+3] = c.A
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i += 4
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}
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}
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case cbG16:
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for x := b.Min.X; x < b.Max.X; x++ {
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c := color.Gray16Model.Convert(m.At(x, y)).(color.Gray16)
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cr[0][i+0] = uint8(c.Y >> 8)
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cr[0][i+1] = uint8(c.Y)
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i += 2
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}
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case cbTC16:
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// We have previously verified that the alpha value is fully opaque.
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for x := b.Min.X; x < b.Max.X; x++ {
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r, g, b, _ := m.At(x, y).RGBA()
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cr[0][i+0] = uint8(r >> 8)
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cr[0][i+1] = uint8(r)
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cr[0][i+2] = uint8(g >> 8)
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cr[0][i+3] = uint8(g)
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cr[0][i+4] = uint8(b >> 8)
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cr[0][i+5] = uint8(b)
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i += 6
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}
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case cbTCA16:
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// Convert from image.Image (which is alpha-premultiplied) to PNG's non-alpha-premultiplied.
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for x := b.Min.X; x < b.Max.X; x++ {
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c := color.NRGBA64Model.Convert(m.At(x, y)).(color.NRGBA64)
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cr[0][i+0] = uint8(c.R >> 8)
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cr[0][i+1] = uint8(c.R)
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cr[0][i+2] = uint8(c.G >> 8)
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cr[0][i+3] = uint8(c.G)
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cr[0][i+4] = uint8(c.B >> 8)
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cr[0][i+5] = uint8(c.B)
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cr[0][i+6] = uint8(c.A >> 8)
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cr[0][i+7] = uint8(c.A)
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i += 8
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}
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}
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// Apply the filter.
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// Skip filter for NoCompression and paletted images (cbP8) as
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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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f = filter(&cr, pr, bpp)
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}
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// Write the compressed bytes.
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if _, err := zw.Write(cr[f]); err != nil {
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return err
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}
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// The current row for y is the previous row for y+1.
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pr, cr[0] = cr[0], pr
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}
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return nil
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}
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// Write the actual image data to one or more IDAT chunks.
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func (e *encoder) writeIDATs() {
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if e.err != nil {
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return
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}
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var bw *bufio.Writer
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bw = bufio.NewWriterSize(e, 1<<15)
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e.err = writeImage(bw, e.m, e.cb, levelToZlib(e.enc.CompressionLevel))
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if e.err != nil {
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return
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}
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e.err = bw.Flush()
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}
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// This function is required because we want the zero value of
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// Encoder.CompressionLevel to map to zlib.DefaultCompression.
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func levelToZlib(l CompressionLevel) int {
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switch l {
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case DefaultCompression:
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return zlib.DefaultCompression
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case NoCompression:
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return zlib.NoCompression
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case BestSpeed:
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return zlib.BestSpeed
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case BestCompression:
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return zlib.BestCompression
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default:
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return zlib.DefaultCompression
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}
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}
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func (e *encoder) writeIEND() { e.writeChunk(nil, "IEND") }
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|
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// Encode writes the Image m to w in PNG format. Any Image may be
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// encoded, but images that are not image.NRGBA might be encoded lossily.
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func Encode(w io.Writer, m image.Image) error {
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var e Encoder
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return e.Encode(w, m)
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}
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// Encode writes the Image m to w in PNG format.
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func (enc *Encoder) Encode(w io.Writer, m image.Image) error {
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// Obviously, negative widths and heights are invalid. Furthermore, the PNG
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// spec section 11.2.2 says that zero is invalid. Excessively large images are
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// also rejected.
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mw, mh := int64(m.Bounds().Dx()), int64(m.Bounds().Dy())
|
|
if mw <= 0 || mh <= 0 || mw >= 1<<32 || mh >= 1<<32 {
|
|
return FormatError("invalid image size: " + strconv.FormatInt(mw, 10) + "x" + strconv.FormatInt(mh, 10))
|
|
}
|
|
|
|
var e encoder
|
|
e.enc = enc
|
|
e.w = w
|
|
e.m = m
|
|
|
|
var pal color.Palette
|
|
// cbP8 encoding needs PalettedImage's ColorIndexAt method.
|
|
if _, ok := m.(image.PalettedImage); ok {
|
|
pal, _ = m.ColorModel().(color.Palette)
|
|
}
|
|
if pal != nil {
|
|
e.cb = cbP8
|
|
} else {
|
|
switch m.ColorModel() {
|
|
case color.GrayModel:
|
|
e.cb = cbG8
|
|
case color.Gray16Model:
|
|
e.cb = cbG16
|
|
case color.RGBAModel, color.NRGBAModel, color.AlphaModel:
|
|
if opaque(m) {
|
|
e.cb = cbTC8
|
|
} else {
|
|
e.cb = cbTCA8
|
|
}
|
|
default:
|
|
if opaque(m) {
|
|
e.cb = cbTC16
|
|
} else {
|
|
e.cb = cbTCA16
|
|
}
|
|
}
|
|
}
|
|
|
|
_, e.err = io.WriteString(w, pngHeader)
|
|
e.writeIHDR()
|
|
if pal != nil {
|
|
e.writePLTEAndTRNS(pal)
|
|
}
|
|
e.writeIDATs()
|
|
e.writeIEND()
|
|
return e.err
|
|
}
|