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Diffstat (limited to 'vendor/golang.org/x/image/tiff/writer.go')
| -rw-r--r-- | vendor/golang.org/x/image/tiff/writer.go | 438 |
1 files changed, 438 insertions, 0 deletions
diff --git a/vendor/golang.org/x/image/tiff/writer.go b/vendor/golang.org/x/image/tiff/writer.go new file mode 100644 index 00000000..c8a01cea --- /dev/null +++ b/vendor/golang.org/x/image/tiff/writer.go @@ -0,0 +1,438 @@ +// Copyright 2012 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 tiff + +import ( + "bytes" + "compress/zlib" + "encoding/binary" + "image" + "io" + "sort" +) + +// The TIFF format allows to choose the order of the different elements freely. +// The basic structure of a TIFF file written by this package is: +// +// 1. Header (8 bytes). +// 2. Image data. +// 3. Image File Directory (IFD). +// 4. "Pointer area" for larger entries in the IFD. + +// We only write little-endian TIFF files. +var enc = binary.LittleEndian + +// An ifdEntry is a single entry in an Image File Directory. +// A value of type dtRational is composed of two 32-bit values, +// thus data contains two uints (numerator and denominator) for a single number. +type ifdEntry struct { + tag int + datatype int + data []uint32 +} + +func (e ifdEntry) putData(p []byte) { + for _, d := range e.data { + switch e.datatype { + case dtByte, dtASCII: + p[0] = byte(d) + p = p[1:] + case dtShort: + enc.PutUint16(p, uint16(d)) + p = p[2:] + case dtLong, dtRational: + enc.PutUint32(p, uint32(d)) + p = p[4:] + } + } +} + +type byTag []ifdEntry + +func (d byTag) Len() int { return len(d) } +func (d byTag) Less(i, j int) bool { return d[i].tag < d[j].tag } +func (d byTag) Swap(i, j int) { d[i], d[j] = d[j], d[i] } + +func encodeGray(w io.Writer, pix []uint8, dx, dy, stride int, predictor bool) error { + if !predictor { + return writePix(w, pix, dy, dx, stride) + } + buf := make([]byte, dx) + for y := 0; y < dy; y++ { + min := y*stride + 0 + max := y*stride + dx + off := 0 + var v0 uint8 + for i := min; i < max; i++ { + v1 := pix[i] + buf[off] = v1 - v0 + v0 = v1 + off++ + } + if _, err := w.Write(buf); err != nil { + return err + } + } + return nil +} + +func encodeGray16(w io.Writer, pix []uint8, dx, dy, stride int, predictor bool) error { + buf := make([]byte, dx*2) + for y := 0; y < dy; y++ { + min := y*stride + 0 + max := y*stride + dx*2 + off := 0 + var v0 uint16 + for i := min; i < max; i += 2 { + // An image.Gray16's Pix is in big-endian order. + v1 := uint16(pix[i])<<8 | uint16(pix[i+1]) + if predictor { + v0, v1 = v1, v1-v0 + } + // We only write little-endian TIFF files. + buf[off+0] = byte(v1) + buf[off+1] = byte(v1 >> 8) + off += 2 + } + if _, err := w.Write(buf); err != nil { + return err + } + } + return nil +} + +func encodeRGBA(w io.Writer, pix []uint8, dx, dy, stride int, predictor bool) error { + if !predictor { + return writePix(w, pix, dy, dx*4, stride) + } + buf := make([]byte, dx*4) + for y := 0; y < dy; y++ { + min := y*stride + 0 + max := y*stride + dx*4 + off := 0 + var r0, g0, b0, a0 uint8 + for i := min; i < max; i += 4 { + r1, g1, b1, a1 := pix[i+0], pix[i+1], pix[i+2], pix[i+3] + buf[off+0] = r1 - r0 + buf[off+1] = g1 - g0 + buf[off+2] = b1 - b0 + buf[off+3] = a1 - a0 + off += 4 + r0, g0, b0, a0 = r1, g1, b1, a1 + } + if _, err := w.Write(buf); err != nil { + return err + } + } + return nil +} + +func encodeRGBA64(w io.Writer, pix []uint8, dx, dy, stride int, predictor bool) error { + buf := make([]byte, dx*8) + for y := 0; y < dy; y++ { + min := y*stride + 0 + max := y*stride + dx*8 + off := 0 + var r0, g0, b0, a0 uint16 + for i := min; i < max; i += 8 { + // An image.RGBA64's Pix is in big-endian order. + r1 := uint16(pix[i+0])<<8 | uint16(pix[i+1]) + g1 := uint16(pix[i+2])<<8 | uint16(pix[i+3]) + b1 := uint16(pix[i+4])<<8 | uint16(pix[i+5]) + a1 := uint16(pix[i+6])<<8 | uint16(pix[i+7]) + if predictor { + r0, r1 = r1, r1-r0 + g0, g1 = g1, g1-g0 + b0, b1 = b1, b1-b0 + a0, a1 = a1, a1-a0 + } + // We only write little-endian TIFF files. + buf[off+0] = byte(r1) + buf[off+1] = byte(r1 >> 8) + buf[off+2] = byte(g1) + buf[off+3] = byte(g1 >> 8) + buf[off+4] = byte(b1) + buf[off+5] = byte(b1 >> 8) + buf[off+6] = byte(a1) + buf[off+7] = byte(a1 >> 8) + off += 8 + } + if _, err := w.Write(buf); err != nil { + return err + } + } + return nil +} + +func encode(w io.Writer, m image.Image, predictor bool) error { + bounds := m.Bounds() + buf := make([]byte, 4*bounds.Dx()) + for y := bounds.Min.Y; y < bounds.Max.Y; y++ { + off := 0 + if predictor { + var r0, g0, b0, a0 uint8 + for x := bounds.Min.X; x < bounds.Max.X; x++ { + r, g, b, a := m.At(x, y).RGBA() + r1 := uint8(r >> 8) + g1 := uint8(g >> 8) + b1 := uint8(b >> 8) + a1 := uint8(a >> 8) + buf[off+0] = r1 - r0 + buf[off+1] = g1 - g0 + buf[off+2] = b1 - b0 + buf[off+3] = a1 - a0 + off += 4 + r0, g0, b0, a0 = r1, g1, b1, a1 + } + } else { + for x := bounds.Min.X; x < bounds.Max.X; x++ { + r, g, b, a := m.At(x, y).RGBA() + buf[off+0] = uint8(r >> 8) + buf[off+1] = uint8(g >> 8) + buf[off+2] = uint8(b >> 8) + buf[off+3] = uint8(a >> 8) + off += 4 + } + } + if _, err := w.Write(buf); err != nil { + return err + } + } + return nil +} + +// writePix writes the internal byte array of an image to w. It is less general +// but much faster then encode. writePix is used when pix directly +// corresponds to one of the TIFF image types. +func writePix(w io.Writer, pix []byte, nrows, length, stride int) error { + if length == stride { + _, err := w.Write(pix[:nrows*length]) + return err + } + for ; nrows > 0; nrows-- { + if _, err := w.Write(pix[:length]); err != nil { + return err + } + pix = pix[stride:] + } + return nil +} + +func writeIFD(w io.Writer, ifdOffset int, d []ifdEntry) error { + var buf [ifdLen]byte + // Make space for "pointer area" containing IFD entry data + // longer than 4 bytes. + parea := make([]byte, 1024) + pstart := ifdOffset + ifdLen*len(d) + 6 + var o int // Current offset in parea. + + // The IFD has to be written with the tags in ascending order. + sort.Sort(byTag(d)) + + // Write the number of entries in this IFD. + if err := binary.Write(w, enc, uint16(len(d))); err != nil { + return err + } + for _, ent := range d { + enc.PutUint16(buf[0:2], uint16(ent.tag)) + enc.PutUint16(buf[2:4], uint16(ent.datatype)) + count := uint32(len(ent.data)) + if ent.datatype == dtRational { + count /= 2 + } + enc.PutUint32(buf[4:8], count) + datalen := int(count * lengths[ent.datatype]) + if datalen <= 4 { + ent.putData(buf[8:12]) + } else { + if (o + datalen) > len(parea) { + newlen := len(parea) + 1024 + for (o + datalen) > newlen { + newlen += 1024 + } + newarea := make([]byte, newlen) + copy(newarea, parea) + parea = newarea + } + ent.putData(parea[o : o+datalen]) + enc.PutUint32(buf[8:12], uint32(pstart+o)) + o += datalen + } + if _, err := w.Write(buf[:]); err != nil { + return err + } + } + // The IFD ends with the offset of the next IFD in the file, + // or zero if it is the last one (page 14). + if err := binary.Write(w, enc, uint32(0)); err != nil { + return err + } + _, err := w.Write(parea[:o]) + return err +} + +// Options are the encoding parameters. +type Options struct { + // Compression is the type of compression used. + Compression CompressionType + // Predictor determines whether a differencing predictor is used; + // if true, instead of each pixel's color, the color difference to the + // preceding one is saved. This improves the compression for certain + // types of images and compressors. For example, it works well for + // photos with Deflate compression. + Predictor bool +} + +// Encode writes the image m to w. opt determines the options used for +// encoding, such as the compression type. If opt is nil, an uncompressed +// image is written. +func Encode(w io.Writer, m image.Image, opt *Options) error { + d := m.Bounds().Size() + + compression := uint32(cNone) + predictor := false + if opt != nil { + compression = opt.Compression.specValue() + // The predictor field is only used with LZW. See page 64 of the spec. + predictor = opt.Predictor && compression == cLZW + } + + _, err := io.WriteString(w, leHeader) + if err != nil { + return err + } + + // Compressed data is written into a buffer first, so that we + // know the compressed size. + var buf bytes.Buffer + // dst holds the destination for the pixel data of the image -- + // either w or a writer to buf. + var dst io.Writer + // imageLen is the length of the pixel data in bytes. + // The offset of the IFD is imageLen + 8 header bytes. + var imageLen int + + switch compression { + case cNone: + dst = w + // Write IFD offset before outputting pixel data. + switch m.(type) { + case *image.Paletted: + imageLen = d.X * d.Y * 1 + case *image.Gray: + imageLen = d.X * d.Y * 1 + case *image.Gray16: + imageLen = d.X * d.Y * 2 + case *image.RGBA64: + imageLen = d.X * d.Y * 8 + case *image.NRGBA64: + imageLen = d.X * d.Y * 8 + default: + imageLen = d.X * d.Y * 4 + } + err = binary.Write(w, enc, uint32(imageLen+8)) + if err != nil { + return err + } + case cDeflate: + dst = zlib.NewWriter(&buf) + } + + pr := uint32(prNone) + photometricInterpretation := uint32(pRGB) + samplesPerPixel := uint32(4) + bitsPerSample := []uint32{8, 8, 8, 8} + extraSamples := uint32(0) + colorMap := []uint32{} + + if predictor { + pr = prHorizontal + } + switch m := m.(type) { + case *image.Paletted: + photometricInterpretation = pPaletted + samplesPerPixel = 1 + bitsPerSample = []uint32{8} + colorMap = make([]uint32, 256*3) + for i := 0; i < 256 && i < len(m.Palette); i++ { + r, g, b, _ := m.Palette[i].RGBA() + colorMap[i+0*256] = uint32(r) + colorMap[i+1*256] = uint32(g) + colorMap[i+2*256] = uint32(b) + } + err = encodeGray(dst, m.Pix, d.X, d.Y, m.Stride, predictor) + case *image.Gray: + photometricInterpretation = pBlackIsZero + samplesPerPixel = 1 + bitsPerSample = []uint32{8} + err = encodeGray(dst, m.Pix, d.X, d.Y, m.Stride, predictor) + case *image.Gray16: + photometricInterpretation = pBlackIsZero + samplesPerPixel = 1 + bitsPerSample = []uint32{16} + err = encodeGray16(dst, m.Pix, d.X, d.Y, m.Stride, predictor) + case *image.NRGBA: + extraSamples = 2 // Unassociated alpha. + err = encodeRGBA(dst, m.Pix, d.X, d.Y, m.Stride, predictor) + case *image.NRGBA64: + extraSamples = 2 // Unassociated alpha. + bitsPerSample = []uint32{16, 16, 16, 16} + err = encodeRGBA64(dst, m.Pix, d.X, d.Y, m.Stride, predictor) + case *image.RGBA: + extraSamples = 1 // Associated alpha. + err = encodeRGBA(dst, m.Pix, d.X, d.Y, m.Stride, predictor) + case *image.RGBA64: + extraSamples = 1 // Associated alpha. + bitsPerSample = []uint32{16, 16, 16, 16} + err = encodeRGBA64(dst, m.Pix, d.X, d.Y, m.Stride, predictor) + default: + extraSamples = 1 // Associated alpha. + err = encode(dst, m, predictor) + } + if err != nil { + return err + } + + if compression != cNone { + if err = dst.(io.Closer).Close(); err != nil { + return err + } + imageLen = buf.Len() + if err = binary.Write(w, enc, uint32(imageLen+8)); err != nil { + return err + } + if _, err = buf.WriteTo(w); err != nil { + return err + } + } + + ifd := []ifdEntry{ + {tImageWidth, dtShort, []uint32{uint32(d.X)}}, + {tImageLength, dtShort, []uint32{uint32(d.Y)}}, + {tBitsPerSample, dtShort, bitsPerSample}, + {tCompression, dtShort, []uint32{compression}}, + {tPhotometricInterpretation, dtShort, []uint32{photometricInterpretation}}, + {tStripOffsets, dtLong, []uint32{8}}, + {tSamplesPerPixel, dtShort, []uint32{samplesPerPixel}}, + {tRowsPerStrip, dtShort, []uint32{uint32(d.Y)}}, + {tStripByteCounts, dtLong, []uint32{uint32(imageLen)}}, + // There is currently no support for storing the image + // resolution, so give a bogus value of 72x72 dpi. + {tXResolution, dtRational, []uint32{72, 1}}, + {tYResolution, dtRational, []uint32{72, 1}}, + {tResolutionUnit, dtShort, []uint32{resPerInch}}, + } + if pr != prNone { + ifd = append(ifd, ifdEntry{tPredictor, dtShort, []uint32{pr}}) + } + if len(colorMap) != 0 { + ifd = append(ifd, ifdEntry{tColorMap, dtShort, colorMap}) + } + if extraSamples > 0 { + ifd = append(ifd, ifdEntry{tExtraSamples, dtShort, []uint32{extraSamples}}) + } + + return writeIFD(w, imageLen+8, ifd) +} |