// div returns a/b rounded to the nearest integer, instead of rounded to zero. func div(a, b int32) int32 { … } var bitCount … type quantIndex … const quantIndexLuminance … const quantIndexChrominance … const nQuantIndex … var unscaledQuant … type huffIndex … const huffIndexLuminanceDC … const huffIndexLuminanceAC … const huffIndexChrominanceDC … const huffIndexChrominanceAC … const nHuffIndex … type huffmanSpec … var theHuffmanSpec … type huffmanLUT … func (h *huffmanLUT) init(s huffmanSpec) { … } var theHuffmanLUT … func init() { … } type writer … type encoder … func (e *encoder) flush() { … } func (e *encoder) write(p []byte) { … } func (e *encoder) writeByte(b byte) { … } // emit emits the least significant nBits bits of bits to the bit-stream. // The precondition is bits < 1<<nBits && nBits <= 16. func (e *encoder) emit(bits, nBits uint32) { … } // emitHuff emits the given value with the given Huffman encoder. func (e *encoder) emitHuff(h huffIndex, value int32) { … } // emitHuffRLE emits a run of runLength copies of value encoded with the given // Huffman encoder. func (e *encoder) emitHuffRLE(h huffIndex, runLength, value int32) { … } // writeMarkerHeader writes the header for a marker with the given length. func (e *encoder) writeMarkerHeader(marker uint8, markerlen int) { … } // writeDQT writes the Define Quantization Table marker. func (e *encoder) writeDQT() { … } // writeSOF0 writes the Start Of Frame (Baseline Sequential) marker. func (e *encoder) writeSOF0(size image.Point, nComponent int) { … } // writeDHT writes the Define Huffman Table marker. func (e *encoder) writeDHT(nComponent int) { … } // writeBlock writes a block of pixel data using the given quantization table, // returning the post-quantized DC value of the DCT-transformed block. b is in // natural (not zig-zag) order. func (e *encoder) writeBlock(b *block, q quantIndex, prevDC int32) int32 { … } // toYCbCr converts the 8x8 region of m whose top-left corner is p to its // YCbCr values. func toYCbCr(m image.Image, p image.Point, yBlock, cbBlock, crBlock *block) { … } // grayToY stores the 8x8 region of m whose top-left corner is p in yBlock. func grayToY(m *image.Gray, p image.Point, yBlock *block) { … } // rgbaToYCbCr is a specialized version of toYCbCr for image.RGBA images. func rgbaToYCbCr(m *image.RGBA, p image.Point, yBlock, cbBlock, crBlock *block) { … } // yCbCrToYCbCr is a specialized version of toYCbCr for image.YCbCr images. func yCbCrToYCbCr(m *image.YCbCr, p image.Point, yBlock, cbBlock, crBlock *block) { … } // scale scales the 16x16 region represented by the 4 src blocks to the 8x8 // dst block. func scale(dst *block, src *[4]block) { … } var sosHeaderY … var sosHeaderYCbCr … // writeSOS writes the StartOfScan marker. func (e *encoder) writeSOS(m image.Image) { … } const DefaultQuality … type Options … // Encode writes the Image m to w in JPEG 4:2:0 baseline format with the given // options. Default parameters are used if a nil *[Options] is passed. func Encode(w io.Writer, m image.Image, o *Options) error { … }
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