zorldo

stdlibwriter.go (14797B)

---

 // Code generated by gen.go. DO NOT EDIT.
 
 // 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 {
 				// 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
 }