diff options
Diffstat (limited to 'src/pkg/image/jpeg/writer.go')
| -rw-r--r-- | src/pkg/image/jpeg/writer.go | 30 |
1 files changed, 13 insertions, 17 deletions
diff --git a/src/pkg/image/jpeg/writer.go b/src/pkg/image/jpeg/writer.go index 52b3dc4e2..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. |