go.image/tiff: encoder support Gray/Gray16/Paletted format

Use these commands to generate testdata:

# TIFF Tools
tiff2bw    video-001.tiff video-001-gray.tiff
tiffmedian video-001.tiff video-001-paletted.tiff

# ImageMagick
convert -depth 16 video-001.tiff      video-001-16bit.tiff
convert -depth 16 video-001-gray.tiff video-001-gray-16bit.tiff

R=nigeltao, bsiegert
CC=golang-dev
https://golang.org/cl/13243047
This commit is contained in:
ChaiShushan 2013-09-13 17:42:53 +10:00 committed by Nigel Tao
parent 864256f267
commit e39b2394e5
6 changed files with 160 additions and 44 deletions

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testdata/video-001-16bit.tiff vendored Normal file

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testdata/video-001-gray-16bit.tiff vendored Normal file

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testdata/video-001-gray.tiff vendored Normal file

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testdata/video-001-paletted.tiff vendored Normal file

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@ -55,13 +55,85 @@ 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] }
// writeImgData writes the raw data of m into w, optionally using a
// differencing predictor.
func writeImgData(w io.Writer, m image.Image, predictor bool) error {
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 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++ {
i := 0
off := 0
if predictor {
var r0, g0, b0, a0 uint8
for x := bounds.Min.X; x < bounds.Max.X; x++ {
@ -70,21 +142,21 @@ func writeImgData(w io.Writer, m image.Image, predictor bool) error {
g1 := uint8(g >> 8)
b1 := uint8(b >> 8)
a1 := uint8(a >> 8)
buf[i+0] = r1 - r0
buf[i+1] = g1 - g0
buf[i+2] = b1 - b0
buf[i+3] = a1 - a0
i += 4
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[i+0] = uint8(r >> 8)
buf[i+1] = uint8(g >> 8)
buf[i+2] = uint8(b >> 8)
buf[i+3] = uint8(a >> 8)
i += 4
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 {
@ -95,7 +167,7 @@ func writeImgData(w io.Writer, m image.Image, predictor bool) error {
}
// writePix writes the internal byte array of an image to w. It is less general
// but much faster then writeImgData. writePix is used when pix directly
// 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 {
@ -180,6 +252,8 @@ type Options struct {
// 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()
predictor := false
compression := uint32(cNone)
if opt != nil {
@ -201,14 +275,21 @@ func Encode(w io.Writer, m image.Image, opt *Options) error {
// imageLen is the length of the pixel data in bytes.
// The offset of the IFD is imageLen + 8 header bytes.
var imageLen int
bounds := m.Bounds()
width, height := bounds.Dx(), bounds.Dy()
switch compression {
case cNone:
dst = w
// Write IFD offset before outputting pixel data.
imageLen = width * height * 4
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
default:
imageLen = d.X * d.Y * 4
}
err = binary.Write(w, enc, uint32(imageLen+8))
if err != nil {
return err
@ -217,23 +298,46 @@ func Encode(w io.Writer, m image.Image, opt *Options) error {
dst = zlib.NewWriter(&buf)
}
var pr uint32 = prNone
var extrasamples uint32 = 1 // Associated alpha (default).
pr := uint32(prNone)
photometricInterpretation := uint32(pRGB)
samplesPerPixel := uint32(4)
bitsPerSample := []uint32{8, 8, 8, 8}
extrasamples := uint32(1) // Associated alpha (default).
colorMap := []uint32{}
if predictor {
pr = prHorizontal
err = writeImgData(dst, m, predictor)
} else {
switch img := m.(type) {
case *image.NRGBA:
extrasamples = 2 // Unassociated alpha.
off := img.PixOffset(img.Rect.Min.X, img.Rect.Min.Y)
err = writePix(dst, img.Pix[off:], img.Rect.Dy(), 4*img.Rect.Dx(), img.Stride)
case *image.RGBA:
off := img.PixOffset(img.Rect.Min.X, img.Rect.Min.Y)
err = writePix(dst, img.Pix[off:], img.Rect.Dy(), 4*img.Rect.Dx(), img.Stride)
default:
err = writeImgData(dst, m, predictor)
}
switch m := m.(type) {
case *image.Paletted:
photometricInterpretation = pPaletted
samplesPerPixel = 3
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.RGBA:
err = encodeRGBA(dst, m.Pix, d.X, d.Y, m.Stride, predictor)
default:
err = encode(dst, m, predictor)
}
if err != nil {
return err
@ -252,15 +356,15 @@ func Encode(w io.Writer, m image.Image, opt *Options) error {
}
}
return writeIFD(w, imageLen+8, []ifdEntry{
{tImageWidth, dtShort, []uint32{uint32(width)}},
{tImageLength, dtShort, []uint32{uint32(height)}},
{tBitsPerSample, dtShort, []uint32{8, 8, 8, 8}},
ifd := []ifdEntry{
{tImageWidth, dtShort, []uint32{uint32(d.X)}},
{tImageLength, dtShort, []uint32{uint32(d.Y)}},
{tBitsPerSample, dtShort, bitsPerSample},
{tCompression, dtShort, []uint32{compression}},
{tPhotometricInterpretation, dtShort, []uint32{pRGB}},
{tPhotometricInterpretation, dtShort, []uint32{photometricInterpretation}},
{tStripOffsets, dtLong, []uint32{8}},
{tSamplesPerPixel, dtShort, []uint32{4}},
{tRowsPerStrip, dtShort, []uint32{uint32(height)}},
{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.
@ -269,5 +373,10 @@ func Encode(w io.Writer, m image.Image, opt *Options) error {
{tResolutionUnit, dtShort, []uint32{resPerInch}},
{tPredictor, dtShort, []uint32{pr}},
{tExtraSamples, dtShort, []uint32{extrasamples}},
})
}
if len(colorMap) != 0 {
ifd = append(ifd, ifdEntry{tColorMap, dtShort, colorMap})
}
return writeIFD(w, imageLen+8, ifd)
}

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@ -17,6 +17,9 @@ var roundtripTests = []struct {
opts *Options
}{
{"video-001.tiff", nil},
{"video-001-gray.tiff", nil},
{"video-001-gray-16bit.tiff", nil},
{"video-001-paletted.tiff", nil},
{"bw-packbits.tiff", nil},
{"video-001.tiff", &Options{Predictor: true}},
{"video-001.tiff", &Options{Compression: Deflate}},
@ -70,16 +73,20 @@ func TestRoundtrip2(t *testing.T) {
compare(t, m0, m1)
}
// BenchmarkEncode benchmarks the encoding of an image.
func BenchmarkEncode(b *testing.B) {
img, err := openImage("video-001.tiff")
func benchmarkEncode(b *testing.B, name string, pixelSize int) {
img, err := openImage(name)
if err != nil {
b.Fatal(err)
}
s := img.Bounds().Size()
b.SetBytes(int64(s.X * s.Y * 4))
b.SetBytes(int64(s.X * s.Y * pixelSize))
b.ResetTimer()
for i := 0; i < b.N; i++ {
Encode(ioutil.Discard, img, nil)
}
}
func BenchmarkEncode(b *testing.B) { benchmarkEncode(b, "video-001.tiff", 4) }
func BenchmarkEncodePaletted(b *testing.B) { benchmarkEncode(b, "video-001-paletted.tiff", 1) }
func BenchmarkEncodeGray(b *testing.B) { benchmarkEncode(b, "video-001-gray.tiff", 1) }
func BenchmarkEncodeGray16(b *testing.B) { benchmarkEncode(b, "video-001-gray-16bit.tiff", 2) }