diff options
Diffstat (limited to 'src/pkg/image/jpeg/writer.go')
| -rw-r--r-- | src/pkg/image/jpeg/writer.go | 62 |
1 files changed, 44 insertions, 18 deletions
diff --git a/src/pkg/image/jpeg/writer.go b/src/pkg/image/jpeg/writer.go index 505cce04f..eddaaefb6 100644 --- a/src/pkg/image/jpeg/writer.go +++ b/src/pkg/image/jpeg/writer.go @@ -221,8 +221,7 @@ type encoder struct { // buf is a scratch buffer. buf [16]byte // bits and nBits are accumulated bits to write to w. - bits uint32 - nBits uint8 + bits, nBits uint32 // quant is the scaled quantization tables. quant [nQuantIndex][blockSize]byte } @@ -250,7 +249,7 @@ func (e *encoder) writeByte(b byte) { // emit emits the least significant nBits bits of bits to the bitstream. // The precondition is bits < 1<<nBits && nBits <= 16. -func (e *encoder) emit(bits uint32, nBits uint8) { +func (e *encoder) emit(bits, nBits uint32) { nBits += e.nBits bits <<= 32 - nBits bits |= e.bits @@ -269,7 +268,7 @@ func (e *encoder) emit(bits uint32, nBits uint8) { // emitHuff emits the given value with the given Huffman encoder. func (e *encoder) emitHuff(h huffIndex, value int) { x := theHuffmanLUT[h][value] - e.emit(x&(1<<24-1), uint8(x>>24)) + e.emit(x&(1<<24-1), x>>24) } // emitHuffRLE emits a run of runLength copies of value encoded with the given @@ -279,11 +278,11 @@ func (e *encoder) emitHuffRLE(h huffIndex, runLength, value int) { if a < 0 { a, b = -value, value-1 } - var nBits uint8 + var nBits uint32 if a < 0x100 { - nBits = bitCount[a] + nBits = uint32(bitCount[a]) } else { - nBits = 8 + bitCount[a>>8] + nBits = 8 + uint32(bitCount[a>>8]) } e.emitHuff(h, runLength<<4|int(nBits)) if nBits > 0 { @@ -302,34 +301,31 @@ func (e *encoder) writeMarkerHeader(marker uint8, markerlen int) { // writeDQT writes the Define Quantization Table marker. func (e *encoder) writeDQT() { - markerlen := 2 - for _, q := range e.quant { - markerlen += 1 + len(q) - } + markerlen := 2 + int(nQuantIndex)*(1+blockSize) e.writeMarkerHeader(dqtMarker, markerlen) - for i, q := range e.quant { + for i := range e.quant { e.writeByte(uint8(i)) - e.write(q[:]) + e.write(e.quant[i][:]) } } // writeSOF0 writes the Start Of Frame (Baseline) marker. func (e *encoder) writeSOF0(size image.Point) { - markerlen := 8 + 3*nComponent + markerlen := 8 + 3*nColorComponent e.writeMarkerHeader(sof0Marker, markerlen) e.buf[0] = 8 // 8-bit color. e.buf[1] = uint8(size.Y >> 8) e.buf[2] = uint8(size.Y & 0xff) e.buf[3] = uint8(size.X >> 8) e.buf[4] = uint8(size.X & 0xff) - e.buf[5] = nComponent - for i := 0; i < nComponent; i++ { + e.buf[5] = nColorComponent + for i := 0; i < nColorComponent; i++ { e.buf[3*i+6] = uint8(i + 1) // We use 4:2:0 chroma subsampling. e.buf[3*i+7] = "\x22\x11\x11"[i] e.buf[3*i+8] = "\x00\x01\x01"[i] } - e.write(e.buf[:3*(nComponent-1)+9]) + e.write(e.buf[:3*(nColorComponent-1)+9]) } // writeDHT writes the Define Huffman Table marker. @@ -391,6 +387,31 @@ func toYCbCr(m image.Image, p image.Point, yBlock, cbBlock, crBlock *block) { } } +// rgbaToYCbCr is a specialized version of toYCbCr for image.RGBA images. +func rgbaToYCbCr(m *image.RGBA, p image.Point, yBlock, cbBlock, crBlock *block) { + b := m.Bounds() + xmax := b.Max.X - 1 + ymax := b.Max.Y - 1 + for j := 0; j < 8; j++ { + sj := p.Y + j + if sj > ymax { + sj = ymax + } + yoff := sj * m.Stride + for i := 0; i < 8; i++ { + sx := p.X + i + if sx > xmax { + sx = xmax + } + col := &m.Pix[yoff+sx] + yy, cb, cr := ycbcr.RGBToYCbCr(col.R, col.G, col.B) + yBlock[8*j+i] = int(yy) + cbBlock[8*j+i] = int(cb) + crBlock[8*j+i] = int(cr) + } + } +} + // scale scales the 16x16 region represented by the 4 src blocks to the 8x8 // dst block. func scale(dst *block, src *[4]block) { @@ -431,13 +452,18 @@ func (e *encoder) writeSOS(m image.Image) { prevDCY, prevDCCb, prevDCCr int ) bounds := m.Bounds() + rgba, _ := m.(*image.RGBA) for y := bounds.Min.Y; y < bounds.Max.Y; y += 16 { for x := bounds.Min.X; x < bounds.Max.X; x += 16 { for i := 0; i < 4; i++ { xOff := (i & 1) * 8 yOff := (i & 2) * 4 p := image.Point{x + xOff, y + yOff} - toYCbCr(m, p, &yBlock, &cbBlock[i], &crBlock[i]) + if rgba != nil { + rgbaToYCbCr(rgba, p, &yBlock, &cbBlock[i], &crBlock[i]) + } else { + toYCbCr(m, p, &yBlock, &cbBlock[i], &crBlock[i]) + } prevDCY = e.writeBlock(&yBlock, 0, prevDCY) } scale(&cBlock, &cbBlock) |