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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
commit | 43a123c1ae6613b3efeed291fa552ecd909d3acf (patch) | |
tree | fd92518b7024bc74031f78a1cf9e454b65e73665 /src/image/png/writer.go | |
parent | Initial commit. (diff) | |
download | golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip |
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/image/png/writer.go')
-rw-r--r-- | src/image/png/writer.go | 666 |
1 files changed, 666 insertions, 0 deletions
diff --git a/src/image/png/writer.go b/src/image/png/writer.go new file mode 100644 index 0000000..0d747da --- /dev/null +++ b/src/image/png/writer.go @@ -0,0 +1,666 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package png + +import ( + "bufio" + "compress/zlib" + "encoding/binary" + "hash/crc32" + "image" + "image/color" + "io" + "strconv" +) + +// Encoder configures encoding PNG images. +type Encoder struct { + CompressionLevel CompressionLevel + + // BufferPool optionally specifies a buffer pool to get temporary + // EncoderBuffers when encoding an image. + BufferPool EncoderBufferPool +} + +// EncoderBufferPool is an interface for getting and returning temporary +// instances of the EncoderBuffer struct. This can be used to reuse buffers +// when encoding multiple images. +type EncoderBufferPool interface { + Get() *EncoderBuffer + Put(*EncoderBuffer) +} + +// EncoderBuffer holds the buffers used for encoding PNG images. +type EncoderBuffer encoder + +type encoder struct { + enc *Encoder + w io.Writer + m image.Image + cb int + err error + header [8]byte + footer [4]byte + tmp [4 * 256]byte + cr [nFilter][]uint8 + pr []uint8 + zw *zlib.Writer + zwLevel int + bw *bufio.Writer +} + +// CompressionLevel indicates the compression level. +type CompressionLevel int + +const ( + DefaultCompression CompressionLevel = 0 + NoCompression CompressionLevel = -1 + BestSpeed CompressionLevel = -2 + BestCompression CompressionLevel = -3 + + // Positive CompressionLevel values are reserved to mean a numeric zlib + // compression level, although that is not implemented yet. +) + +type opaquer interface { + Opaque() bool +} + +// Returns whether or not the image is fully opaque. +func opaque(m image.Image) bool { + if o, ok := m.(opaquer); ok { + return o.Opaque() + } + b := m.Bounds() + for y := b.Min.Y; y < b.Max.Y; y++ { + for x := b.Min.X; x < b.Max.X; x++ { + _, _, _, a := m.At(x, y).RGBA() + if a != 0xffff { + return false + } + } + } + return true +} + +// The absolute value of a byte interpreted as a signed int8. +func abs8(d uint8) int { + if d < 128 { + return int(d) + } + return 256 - int(d) +} + +func (e *encoder) writeChunk(b []byte, name string) { + if e.err != nil { + return + } + n := uint32(len(b)) + if int(n) != len(b) { + e.err = UnsupportedError(name + " chunk is too large: " + strconv.Itoa(len(b))) + return + } + binary.BigEndian.PutUint32(e.header[:4], n) + e.header[4] = name[0] + e.header[5] = name[1] + e.header[6] = name[2] + e.header[7] = name[3] + crc := crc32.NewIEEE() + crc.Write(e.header[4:8]) + crc.Write(b) + binary.BigEndian.PutUint32(e.footer[:4], crc.Sum32()) + + _, e.err = e.w.Write(e.header[:8]) + if e.err != nil { + return + } + _, e.err = e.w.Write(b) + if e.err != nil { + return + } + _, e.err = e.w.Write(e.footer[:4]) +} + +func (e *encoder) writeIHDR() { + b := e.m.Bounds() + binary.BigEndian.PutUint32(e.tmp[0:4], uint32(b.Dx())) + binary.BigEndian.PutUint32(e.tmp[4:8], uint32(b.Dy())) + // Set bit depth and color type. + switch e.cb { + case cbG8: + e.tmp[8] = 8 + e.tmp[9] = ctGrayscale + case cbTC8: + e.tmp[8] = 8 + e.tmp[9] = ctTrueColor + case cbP8: + e.tmp[8] = 8 + e.tmp[9] = ctPaletted + case cbP4: + e.tmp[8] = 4 + e.tmp[9] = ctPaletted + case cbP2: + e.tmp[8] = 2 + e.tmp[9] = ctPaletted + case cbP1: + e.tmp[8] = 1 + e.tmp[9] = ctPaletted + case cbTCA8: + e.tmp[8] = 8 + e.tmp[9] = ctTrueColorAlpha + case cbG16: + e.tmp[8] = 16 + e.tmp[9] = ctGrayscale + case cbTC16: + e.tmp[8] = 16 + e.tmp[9] = ctTrueColor + case cbTCA16: + e.tmp[8] = 16 + e.tmp[9] = ctTrueColorAlpha + } + e.tmp[10] = 0 // default compression method + e.tmp[11] = 0 // default filter method + e.tmp[12] = 0 // non-interlaced + e.writeChunk(e.tmp[:13], "IHDR") +} + +func (e *encoder) writePLTEAndTRNS(p color.Palette) { + if len(p) < 1 || len(p) > 256 { + e.err = FormatError("bad palette length: " + strconv.Itoa(len(p))) + return + } + last := -1 + for i, c := range p { + c1 := color.NRGBAModel.Convert(c).(color.NRGBA) + e.tmp[3*i+0] = c1.R + e.tmp[3*i+1] = c1.G + e.tmp[3*i+2] = c1.B + if c1.A != 0xff { + last = i + } + e.tmp[3*256+i] = c1.A + } + e.writeChunk(e.tmp[:3*len(p)], "PLTE") + if last != -1 { + e.writeChunk(e.tmp[3*256:3*256+1+last], "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. +// +// This method should only be called from writeIDATs (via writeImage). +// No other code should treat an encoder as an io.Writer. +func (e *encoder) Write(b []byte) (int, error) { + e.writeChunk(b, "IDAT") + if e.err != nil { + return 0, e.err + } + return len(b), nil +} + +// 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 *[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 + // in their enumeration order (ftNone, ftSub, ftUp, ftAverage, ftPaeth). + cdat0 := cr[0][1:] + cdat1 := cr[1][1:] + cdat2 := cr[2][1:] + cdat3 := cr[3][1:] + cdat4 := cr[4][1:] + pdat := pr[1:] + n := len(cdat0) + + // The up filter. + sum := 0 + for i := 0; i < n; i++ { + cdat2[i] = cdat0[i] - pdat[i] + sum += abs8(cdat2[i]) + } + best := sum + filter := ftUp + + // The Paeth filter. + sum = 0 + for i := 0; i < bpp; i++ { + cdat4[i] = cdat0[i] - pdat[i] + sum += abs8(cdat4[i]) + } + for i := bpp; i < n; i++ { + cdat4[i] = cdat0[i] - paeth(cdat0[i-bpp], pdat[i], pdat[i-bpp]) + sum += abs8(cdat4[i]) + if sum >= best { + break + } + } + if sum < best { + best = sum + filter = ftPaeth + } + + // The none filter. + sum = 0 + for i := 0; i < n; i++ { + sum += abs8(cdat0[i]) + if sum >= best { + break + } + } + if sum < best { + best = sum + filter = ftNone + } + + // The sub filter. + sum = 0 + for i := 0; i < bpp; i++ { + cdat1[i] = cdat0[i] + sum += abs8(cdat1[i]) + } + for i := bpp; i < n; i++ { + cdat1[i] = cdat0[i] - cdat0[i-bpp] + sum += abs8(cdat1[i]) + if sum >= best { + break + } + } + if sum < best { + best = sum + filter = ftSub + } + + // The average filter. + sum = 0 + for i := 0; i < bpp; i++ { + cdat3[i] = cdat0[i] - pdat[i]/2 + sum += abs8(cdat3[i]) + } + for i := bpp; i < n; i++ { + cdat3[i] = cdat0[i] - uint8((int(cdat0[i-bpp])+int(pdat[i]))/2) + sum += abs8(cdat3[i]) + if sum >= best { + break + } + } + if sum < best { + filter = ftAverage + } + + return filter +} + +func zeroMemory(v []uint8) { + for i := range v { + v[i] = 0 + } +} + +func (e *encoder) writeImage(w io.Writer, m image.Image, cb int, level int) error { + if e.zw == nil || e.zwLevel != level { + zw, err := zlib.NewWriterLevel(w, level) + if err != nil { + return err + } + e.zw = zw + e.zwLevel = level + } else { + e.zw.Reset(w) + } + defer e.zw.Close() + + bitsPerPixel := 0 + + switch cb { + case cbG8: + bitsPerPixel = 8 + case cbTC8: + bitsPerPixel = 24 + case cbP8: + bitsPerPixel = 8 + case cbP4: + bitsPerPixel = 4 + case cbP2: + bitsPerPixel = 2 + case cbP1: + bitsPerPixel = 1 + case cbTCA8: + bitsPerPixel = 32 + case cbTC16: + bitsPerPixel = 48 + case cbTCA16: + bitsPerPixel = 64 + case cbG16: + bitsPerPixel = 16 + } + + // cr[*] and pr are the bytes for the current and previous row. + // cr[0] is unfiltered (or equivalently, filtered with the ftNone filter). + // cr[ft], for non-zero filter types ft, are buffers for transforming cr[0] under the + // other PNG filter types. These buffers are allocated once and re-used for each row. + // The +1 is for the per-row filter type, which is at cr[*][0]. + b := m.Bounds() + sz := 1 + (bitsPerPixel*b.Dx()+7)/8 + for i := range e.cr { + if cap(e.cr[i]) < sz { + e.cr[i] = make([]uint8, sz) + } else { + e.cr[i] = e.cr[i][:sz] + } + e.cr[i][0] = uint8(i) + } + cr := e.cr + if cap(e.pr) < sz { + e.pr = make([]uint8, sz) + } else { + e.pr = e.pr[:sz] + zeroMemory(e.pr) + } + pr := e.pr + + gray, _ := m.(*image.Gray) + rgba, _ := m.(*image.RGBA) + paletted, _ := m.(*image.Paletted) + nrgba, _ := m.(*image.NRGBA) + + for y := b.Min.Y; y < b.Max.Y; y++ { + // Convert from colors to bytes. + i := 1 + switch cb { + case cbG8: + if gray != nil { + offset := (y - b.Min.Y) * gray.Stride + copy(cr[0][1:], gray.Pix[offset:offset+b.Dx()]) + } else { + for x := b.Min.X; x < b.Max.X; x++ { + c := color.GrayModel.Convert(m.At(x, y)).(color.Gray) + cr[0][i] = c.Y + i++ + } + } + case cbTC8: + // We have previously verified that the alpha value is fully opaque. + cr0 := cr[0] + stride, pix := 0, []byte(nil) + if rgba != nil { + stride, pix = rgba.Stride, rgba.Pix + } else if nrgba != nil { + stride, pix = nrgba.Stride, nrgba.Pix + } + if stride != 0 { + j0 := (y - b.Min.Y) * stride + j1 := j0 + b.Dx()*4 + for j := j0; j < j1; j += 4 { + cr0[i+0] = pix[j+0] + cr0[i+1] = pix[j+1] + cr0[i+2] = pix[j+2] + i += 3 + } + } else { + for x := b.Min.X; x < b.Max.X; x++ { + r, g, b, _ := m.At(x, y).RGBA() + cr0[i+0] = uint8(r >> 8) + cr0[i+1] = uint8(g >> 8) + cr0[i+2] = uint8(b >> 8) + i += 3 + } + } + case cbP8: + if paletted != nil { + offset := (y - b.Min.Y) * paletted.Stride + copy(cr[0][1:], paletted.Pix[offset:offset+b.Dx()]) + } else { + pi := m.(image.PalettedImage) + for x := b.Min.X; x < b.Max.X; x++ { + cr[0][i] = pi.ColorIndexAt(x, y) + i += 1 + } + } + + case cbP4, cbP2, cbP1: + pi := m.(image.PalettedImage) + + var a uint8 + var c int + pixelsPerByte := 8 / bitsPerPixel + for x := b.Min.X; x < b.Max.X; x++ { + a = a<<uint(bitsPerPixel) | pi.ColorIndexAt(x, y) + c++ + if c == pixelsPerByte { + cr[0][i] = a + i += 1 + a = 0 + c = 0 + } + } + if c != 0 { + for c != pixelsPerByte { + a = a << uint(bitsPerPixel) + c++ + } + cr[0][i] = a + } + + case cbTCA8: + if nrgba != nil { + offset := (y - b.Min.Y) * nrgba.Stride + copy(cr[0][1:], nrgba.Pix[offset:offset+b.Dx()*4]) + } else if rgba != nil { + dst := cr[0][1:] + src := rgba.Pix[rgba.PixOffset(b.Min.X, y):rgba.PixOffset(b.Max.X, y)] + for ; len(src) >= 4; dst, src = dst[4:], src[4:] { + d := (*[4]byte)(dst) + s := (*[4]byte)(src) + if s[3] == 0x00 { + d[0] = 0 + d[1] = 0 + d[2] = 0 + d[3] = 0 + } else if s[3] == 0xff { + copy(d[:], s[:]) + } else { + // This code does the same as color.NRGBAModel.Convert( + // rgba.At(x, y)).(color.NRGBA) but with no extra memory + // allocations or interface/function call overhead. + // + // The multiplier m combines 0x101 (which converts + // 8-bit color to 16-bit color) and 0xffff (which, when + // combined with the division-by-a, converts from + // alpha-premultiplied to non-alpha-premultiplied). + const m = 0x101 * 0xffff + a := uint32(s[3]) * 0x101 + d[0] = uint8((uint32(s[0]) * m / a) >> 8) + d[1] = uint8((uint32(s[1]) * m / a) >> 8) + d[2] = uint8((uint32(s[2]) * m / a) >> 8) + d[3] = s[3] + } + } + } else { + // 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 := color.NRGBAModel.Convert(m.At(x, y)).(color.NRGBA) + 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 := color.Gray16Model.Convert(m.At(x, y)).(color.Gray16) + 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++ { + r, g, b, _ := m.At(x, y).RGBA() + 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 := color.NRGBA64Model.Convert(m.At(x, y)).(color.NRGBA64) + 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. + // Skip filter for NoCompression and paletted images (cbP8) as + // "filters are rarely useful on palette images" and will result + // in larger files (see http://www.libpng.org/pub/png/book/chapter09.html). + f := ftNone + if level != zlib.NoCompression && cb != cbP8 && cb != cbP4 && cb != cbP2 && cb != cbP1 { + // Since we skip paletted images we don't have to worry about + // bitsPerPixel not being a multiple of 8 + bpp := bitsPerPixel / 8 + f = filter(&cr, pr, bpp) + } + + // Write the compressed bytes. + if _, err := e.zw.Write(cr[f]); err != nil { + return err + } + + // The current row for y is the previous row for y+1. + pr, cr[0] = cr[0], pr + } + return nil +} + +// Write the actual image data to one or more IDAT chunks. +func (e *encoder) writeIDATs() { + if e.err != nil { + return + } + if e.bw == nil { + e.bw = bufio.NewWriterSize(e, 1<<15) + } else { + e.bw.Reset(e) + } + e.err = e.writeImage(e.bw, e.m, e.cb, levelToZlib(e.enc.CompressionLevel)) + if e.err != nil { + return + } + e.err = e.bw.Flush() +} + +// This function is required because we want the zero value of +// Encoder.CompressionLevel to map to zlib.DefaultCompression. +func levelToZlib(l CompressionLevel) int { + switch l { + case DefaultCompression: + return zlib.DefaultCompression + case NoCompression: + return zlib.NoCompression + case BestSpeed: + return zlib.BestSpeed + case BestCompression: + return zlib.BestCompression + default: + return zlib.DefaultCompression + } +} + +func (e *encoder) writeIEND() { e.writeChunk(nil, "IEND") } + +// Encode writes the Image m to w in PNG format. Any Image may be +// encoded, but images that are not image.NRGBA might be encoded lossily. +func Encode(w io.Writer, m image.Image) error { + var e Encoder + return e.Encode(w, m) +} + +// Encode writes the Image m to w in PNG format. +func (enc *Encoder) Encode(w io.Writer, m image.Image) error { + // Obviously, negative widths and heights are invalid. Furthermore, the PNG + // spec section 11.2.2 says that zero is invalid. Excessively large images are + // also rejected. + 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 + if enc.BufferPool != nil { + buffer := enc.BufferPool.Get() + e = (*encoder)(buffer) + + } + if e == nil { + e = &encoder{} + } + if enc.BufferPool != nil { + defer enc.BufferPool.Put((*EncoderBuffer)(e)) + } + + 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 { + if len(pal) <= 2 { + e.cb = cbP1 + } else if len(pal) <= 4 { + e.cb = cbP2 + } else if len(pal) <= 16 { + e.cb = cbP4 + } else { + 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 +} |