go.image/vp8, go.image/webp: new packages, copied from
code.google.com/p/vp8-go
This is a straight copy, followed by import path updates.
LGTM=r
R=r, mirtchovski, oleku.konko
CC=golang-codereviews
https://golang.org/cl/79320043
diff --git a/vp8/decode.go b/vp8/decode.go
new file mode 100644
index 0000000..9cb2a71
--- /dev/null
+++ b/vp8/decode.go
@@ -0,0 +1,356 @@
+// Copyright 2011 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 vp8 implements a vp8 image and video decoder.
+//
+// The VP8 specification is at:
+// http://datatracker.ietf.org/doc/rfc6386/
+package vp8
+
+// This file implements the top-level decoding algorithm.
+
+import (
+ "errors"
+ "image"
+ "io"
+)
+
+// limitReader wraps an io.Reader to read at most n bytes from it.
+type limitReader struct {
+ r io.Reader
+ n int
+}
+
+// ReadFull reads exactly len(p) bytes into p.
+func (r *limitReader) ReadFull(p []byte) error {
+ if len(p) > r.n {
+ return io.ErrUnexpectedEOF
+ }
+ n, err := io.ReadFull(r.r, p)
+ r.n -= n
+ return err
+}
+
+// FrameHeader is a frame header, as specified in section 9.1.
+type FrameHeader struct {
+ KeyFrame bool
+ VersionNumber uint8
+ ShowFrame bool
+ FirstPartitionLen uint32
+ Width int
+ Height int
+ XScale uint8
+ YScale uint8
+}
+
+const (
+ nSegment = 4
+ nSegmentProb = 3
+)
+
+// segmentHeader holds segment-related header information.
+type segmentHeader struct {
+ useSegment bool
+ updateMap bool
+ relativeDelta bool
+ quantizer [nSegment]int8
+ filterStrength [nSegment]int8
+ prob [nSegmentProb]uint8
+}
+
+const (
+ nRefLFDelta = 4
+ nModeLFDelta = 4
+)
+
+// filterHeader holds filter-related header information.
+type filterHeader struct {
+ simple bool
+ level int8
+ sharpness uint8
+ useLFDelta bool
+ refLFDelta [nRefLFDelta]int8
+ modeLFDelta [nModeLFDelta]int8
+ perSegmentLevel [nSegment]int8
+}
+
+// mb is the per-macroblock decode state. A decoder maintains mbw+1 of these
+// as it is decoding macroblocks left-to-right and top-to-bottom: mbw for the
+// macroblocks in the row above, and one for the macroblock to the left.
+type mb struct {
+ // pred is the predictor mode for the 4 bottom or right 4x4 luma regions.
+ pred [4]uint8
+ // nzMask is a mask of 8 bits: 4 for the bottom or right 4x4 luma regions,
+ // and 2 + 2 for the bottom or right 4x4 chroma regions. A 1 bit indicates
+ // that that region has non-zero coefficients.
+ nzMask uint8
+ // nzY16 is a 0/1 value that is 1 if the macroblock used Y16 prediction and
+ // had non-zero coefficients.
+ nzY16 uint8
+}
+
+// Decoder decodes VP8 bitstreams into frames. Decoding one frame consists of
+// calling Init, DecodeFrameHeader and then DecodeFrame in that order.
+// A Decoder can be re-used to decode multiple frames.
+type Decoder struct {
+ // r is the input bitsream.
+ r limitReader
+ // scratch is a scratch buffer.
+ scratch [8]byte
+ // img is the YCbCr image to decode into.
+ img *image.YCbCr
+ // mbw and mbh are the number of 16x16 macroblocks wide and high the image is.
+ mbw, mbh int
+ // frameHeader is the frame header. When decoding multiple frames,
+ // frames that aren't key frames will inherit the Width, Height,
+ // XScale and YScale of the most recent key frame.
+ frameHeader FrameHeader
+ // Other headers.
+ segmentHeader segmentHeader
+ filterHeader filterHeader
+ // The image data is divided into a number of independent partitions.
+ // There is 1 "first partition" and between 1 and 8 "other partitions"
+ // for coefficient data.
+ fp partition
+ op [8]partition
+ nOP int
+ // Quantization factors.
+ quant [nSegment]quant
+ // DCT/WHT coefficient decoding probabilities.
+ tokenProb [nPlane][nBand][nContext][nProb]uint8
+ useSkipProb bool
+ skipProb uint8
+
+ // The eight fields below relate to the current macroblock being decoded.
+ //
+ // Segment-based adjustments.
+ segment int
+ // Per-macroblock state for the macroblock immediately left of and those
+ // macroblocks immediately above the current macroblock.
+ leftMB mb
+ upMB []mb
+ // Bitmasks for which 4x4 regions of coeff contain non-zero coefficients.
+ nzDCMask, nzACMask uint32
+ // Predictor modes.
+ usePredY16 bool
+ predY16 uint8
+ predC8 uint8
+ predY4 [4][4]uint8
+
+ // The two fields below form a workspace for reconstructing a macroblock.
+ // Their specific sizes are documented in reconstruct.go.
+ coeff [1*16*16 + 2*8*8 + 1*4*4]int16
+ ybr [1 + 16 + 1 + 8][32]uint8
+}
+
+// NewDecoder returns a new Decoder.
+func NewDecoder() *Decoder {
+ return &Decoder{}
+}
+
+// Init initializes the decoder to read at most n bytes from r.
+func (d *Decoder) Init(r io.Reader, n int) {
+ d.r = limitReader{r, n}
+}
+
+// DecodeFrameHeader decodes the frame header.
+func (d *Decoder) DecodeFrameHeader() (fh FrameHeader, err error) {
+ // All frame headers are at least 3 bytes long.
+ b := d.scratch[:3]
+ if err = d.r.ReadFull(b); err != nil {
+ return
+ }
+ d.frameHeader.KeyFrame = (b[0] & 1) == 0
+ d.frameHeader.VersionNumber = (b[0] >> 1) & 7
+ d.frameHeader.ShowFrame = (b[0]>>4)&1 == 1
+ d.frameHeader.FirstPartitionLen = uint32(b[0])>>5 | uint32(b[1])<<3 | uint32(b[2])<<11
+ if !d.frameHeader.KeyFrame {
+ return d.frameHeader, nil
+ }
+ // Frame headers for key frames are an additional 7 bytes long.
+ b = d.scratch[:7]
+ if err = d.r.ReadFull(b); err != nil {
+ return
+ }
+ // Check the magic sync code.
+ if b[0] != 0x9d || b[1] != 0x01 || b[2] != 0x2a {
+ err = errors.New("vp8: invalid format")
+ return
+ }
+ d.frameHeader.Width = int(b[4]&0x3f)<<8 | int(b[3])
+ d.frameHeader.Height = int(b[6]&0x3f)<<8 | int(b[5])
+ d.frameHeader.XScale = b[4] >> 6
+ d.frameHeader.YScale = b[6] >> 6
+ d.mbw = (d.frameHeader.Width + 0x0f) >> 4
+ d.mbh = (d.frameHeader.Height + 0x0f) >> 4
+ d.segmentHeader = segmentHeader{
+ prob: [3]uint8{0xff, 0xff, 0xff},
+ }
+ d.tokenProb = defaultTokenProb
+ d.segment = 0
+ return d.frameHeader, nil
+}
+
+// ensureImg ensures that d.img is large enough to hold the decoded frame.
+func (d *Decoder) ensureImg() {
+ if d.img != nil {
+ p0, p1 := d.img.Rect.Min, d.img.Rect.Max
+ if p0.X == 0 && p0.Y == 0 && p1.X >= 16*d.mbw && p1.Y >= 16*d.mbh {
+ return
+ }
+ }
+ m := image.NewYCbCr(image.Rect(0, 0, 16*d.mbw, 16*d.mbh), image.YCbCrSubsampleRatio420)
+ d.img = m.SubImage(image.Rect(0, 0, d.frameHeader.Width, d.frameHeader.Height)).(*image.YCbCr)
+ d.upMB = make([]mb, d.mbw)
+}
+
+// parseSegmentHeader parses the segment header, as specified in section 9.3.
+func (d *Decoder) parseSegmentHeader() {
+ d.segmentHeader.useSegment = d.fp.readBit(uniformProb)
+ if !d.segmentHeader.useSegment {
+ d.segmentHeader.updateMap = false
+ return
+ }
+ d.segmentHeader.updateMap = d.fp.readBit(uniformProb)
+ if d.fp.readBit(uniformProb) {
+ d.segmentHeader.relativeDelta = !d.fp.readBit(uniformProb)
+ for i := range d.segmentHeader.quantizer {
+ d.segmentHeader.quantizer[i] = int8(d.fp.readOptionalInt(uniformProb, 7))
+ }
+ for i := range d.segmentHeader.filterStrength {
+ d.segmentHeader.filterStrength[i] = int8(d.fp.readOptionalInt(uniformProb, 6))
+ }
+ }
+ if !d.segmentHeader.updateMap {
+ return
+ }
+ for i := range d.segmentHeader.prob {
+ if d.fp.readBit(uniformProb) {
+ d.segmentHeader.prob[i] = uint8(d.fp.readUint(uniformProb, 8))
+ } else {
+ d.segmentHeader.prob[i] = 0xff
+ }
+ }
+}
+
+// parseFilterHeader parses the filter header, as specified in section 9.4.
+func (d *Decoder) parseFilterHeader() {
+ d.filterHeader.simple = d.fp.readBit(uniformProb)
+ d.filterHeader.level = int8(d.fp.readUint(uniformProb, 6))
+ d.filterHeader.sharpness = uint8(d.fp.readUint(uniformProb, 3))
+ d.filterHeader.useLFDelta = d.fp.readBit(uniformProb)
+ if d.filterHeader.useLFDelta && d.fp.readBit(uniformProb) {
+ for i := range d.filterHeader.refLFDelta {
+ d.filterHeader.refLFDelta[i] = int8(d.fp.readOptionalInt(uniformProb, 6))
+ }
+ for i := range d.filterHeader.modeLFDelta {
+ d.filterHeader.modeLFDelta[i] = int8(d.fp.readOptionalInt(uniformProb, 6))
+ }
+ }
+ if d.filterHeader.level == 0 {
+ return
+ }
+ if d.segmentHeader.useSegment {
+ for i := range d.filterHeader.perSegmentLevel {
+ strength := d.segmentHeader.filterStrength[i]
+ if d.segmentHeader.relativeDelta {
+ strength += d.filterHeader.level
+ }
+ d.filterHeader.perSegmentLevel[i] = strength
+ }
+ } else {
+ d.filterHeader.perSegmentLevel[0] = d.filterHeader.level
+ }
+}
+
+// parseOtherPartitions parses the other partitions, as specified in section 9.5.
+func (d *Decoder) parseOtherPartitions() error {
+ buf := make([]byte, d.r.n)
+ if err := d.r.ReadFull(buf); err != nil {
+ return err
+ }
+ d.nOP = 1 << d.fp.readUint(uniformProb, 2)
+ n := 3 * (d.nOP - 1)
+ if n > len(buf) {
+ return io.ErrUnexpectedEOF
+ }
+ partLen, buf := buf[:n], buf[n:]
+ for i := 0; i < d.nOP-1; i++ {
+ m := int(partLen[3*i+0]) | int(partLen[3*i+1])<<8 | int(partLen[3*i+2])<<16
+ if m > len(buf) {
+ return io.ErrUnexpectedEOF
+ }
+ d.op[i].init(buf[:m])
+ buf = buf[m:]
+ }
+ d.op[d.nOP-1].init(buf)
+ return nil
+}
+
+// parseOtherHeaders parses header information other than the frame header.
+func (d *Decoder) parseOtherHeaders() error {
+ // Initialize and parse the first partition.
+ firstPartition := make([]byte, d.frameHeader.FirstPartitionLen)
+ if err := d.r.ReadFull(firstPartition); err != nil {
+ return err
+ }
+ d.fp.init(firstPartition)
+ if d.frameHeader.KeyFrame {
+ // Read and ignore the color space and pixel clamp values. They are
+ // specified in section 9.2, but are unimplemented.
+ d.fp.readBit(uniformProb)
+ d.fp.readBit(uniformProb)
+ }
+ d.parseSegmentHeader()
+ d.parseFilterHeader()
+ if err := d.parseOtherPartitions(); err != nil {
+ return err
+ }
+ d.parseQuant()
+ if !d.frameHeader.KeyFrame {
+ // Golden and AltRef frames are specified in section 9.7.
+ // TODO(nigeltao): implement. Note that they are only used for video, not still images.
+ return errors.New("vp8: Golden / AltRef frames are not implemented")
+ }
+ // Read and ignore the refreshLastFrameBuffer bit, specified in section 9.8.
+ // It applies only to video, and not still images.
+ d.fp.readBit(uniformProb)
+ d.parseTokenProb()
+ d.useSkipProb = d.fp.readBit(uniformProb)
+ if d.useSkipProb {
+ d.skipProb = uint8(d.fp.readUint(uniformProb, 8))
+ }
+ if d.fp.unexpectedEOF {
+ return io.ErrUnexpectedEOF
+ }
+ return nil
+}
+
+// DecodeFrame decodes the frame and returns it as an YCbCr image.
+// The image's contents are valid up until the next call to Decoder.Init.
+func (d *Decoder) DecodeFrame() (*image.YCbCr, error) {
+ d.ensureImg()
+ if err := d.parseOtherHeaders(); err != nil {
+ return nil, err
+ }
+ for mbx := 0; mbx < d.mbw; mbx++ {
+ d.upMB[mbx] = mb{}
+ }
+ for mby := 0; mby < d.mbh; mby++ {
+ d.leftMB = mb{}
+ for mbx := 0; mbx < d.mbw; mbx++ {
+ d.reconstruct(mbx, mby)
+ }
+ // TODO(nigeltao): filter, as specified in chapter 15.
+ }
+ if d.fp.unexpectedEOF {
+ return nil, io.ErrUnexpectedEOF
+ }
+ for i := 0; i < d.nOP; i++ {
+ if d.op[i].unexpectedEOF {
+ return nil, io.ErrUnexpectedEOF
+ }
+ }
+ return d.img, nil
+}
diff --git a/vp8/idct.go b/vp8/idct.go
new file mode 100644
index 0000000..929af2c
--- /dev/null
+++ b/vp8/idct.go
@@ -0,0 +1,98 @@
+// Copyright 2011 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 vp8
+
+// This file implements the inverse Discrete Cosine Transform and the inverse
+// Walsh Hadamard Transform (WHT), as specified in sections 14.3 and 14.4.
+
+func clip8(i int32) uint8 {
+ if i < 0 {
+ return 0
+ }
+ if i > 255 {
+ return 255
+ }
+ return uint8(i)
+}
+
+func (z *Decoder) inverseDCT4(y, x, coeffBase int) {
+ const (
+ c1 = 85627 // 65536 * cos(pi/8) * sqrt(2).
+ c2 = 35468 // 65536 * sin(pi/8) * sqrt(2).
+ )
+ var m [4][4]int32
+ for i := 0; i < 4; i++ {
+ a := int32(z.coeff[coeffBase+0]) + int32(z.coeff[coeffBase+8])
+ b := int32(z.coeff[coeffBase+0]) - int32(z.coeff[coeffBase+8])
+ c := (int32(z.coeff[coeffBase+4])*c2)>>16 - (int32(z.coeff[coeffBase+12])*c1)>>16
+ d := (int32(z.coeff[coeffBase+4])*c1)>>16 + (int32(z.coeff[coeffBase+12])*c2)>>16
+ m[i][0] = a + d
+ m[i][1] = b + c
+ m[i][2] = b - c
+ m[i][3] = a - d
+ coeffBase++
+ }
+ for j := 0; j < 4; j++ {
+ dc := m[0][j] + 4
+ a := dc + m[2][j]
+ b := dc - m[2][j]
+ c := (m[1][j]*c2)>>16 - (m[3][j]*c1)>>16
+ d := (m[1][j]*c1)>>16 + (m[3][j]*c2)>>16
+ z.ybr[y+j][x+0] = clip8(int32(z.ybr[y+j][x+0]) + (a+d)>>3)
+ z.ybr[y+j][x+1] = clip8(int32(z.ybr[y+j][x+1]) + (b+c)>>3)
+ z.ybr[y+j][x+2] = clip8(int32(z.ybr[y+j][x+2]) + (b-c)>>3)
+ z.ybr[y+j][x+3] = clip8(int32(z.ybr[y+j][x+3]) + (a-d)>>3)
+ }
+}
+
+func (z *Decoder) inverseDCT4DCOnly(y, x, coeffBase int) {
+ dc := (int32(z.coeff[coeffBase+0]) + 4) >> 3
+ for j := 0; j < 4; j++ {
+ for i := 0; i < 4; i++ {
+ z.ybr[y+j][x+i] = clip8(int32(z.ybr[y+j][x+i]) + dc)
+ }
+ }
+}
+
+func (z *Decoder) inverseDCT8(y, x, coeffBase int) {
+ z.inverseDCT4(y+0, x+0, coeffBase+0*16)
+ z.inverseDCT4(y+0, x+4, coeffBase+1*16)
+ z.inverseDCT4(y+4, x+0, coeffBase+2*16)
+ z.inverseDCT4(y+4, x+4, coeffBase+3*16)
+}
+
+func (z *Decoder) inverseDCT8DCOnly(y, x, coeffBase int) {
+ z.inverseDCT4DCOnly(y+0, x+0, coeffBase+0*16)
+ z.inverseDCT4DCOnly(y+0, x+4, coeffBase+1*16)
+ z.inverseDCT4DCOnly(y+4, x+0, coeffBase+2*16)
+ z.inverseDCT4DCOnly(y+4, x+4, coeffBase+3*16)
+}
+
+func (d *Decoder) inverseWHT16() {
+ var m [16]int32
+ for i := 0; i < 4; i++ {
+ a0 := int32(d.coeff[384+0+i]) + int32(d.coeff[384+12+i])
+ a1 := int32(d.coeff[384+4+i]) + int32(d.coeff[384+8+i])
+ a2 := int32(d.coeff[384+4+i]) - int32(d.coeff[384+8+i])
+ a3 := int32(d.coeff[384+0+i]) - int32(d.coeff[384+12+i])
+ m[0+i] = a0 + a1
+ m[8+i] = a0 - a1
+ m[4+i] = a3 + a2
+ m[12+i] = a3 - a2
+ }
+ out := 0
+ for i := 0; i < 4; i++ {
+ dc := m[0+i*4] + 3
+ a0 := dc + m[3+i*4]
+ a1 := m[1+i*4] + m[2+i*4]
+ a2 := m[1+i*4] - m[2+i*4]
+ a3 := dc - m[3+i*4]
+ d.coeff[out+0] = int16((a0 + a1) >> 3)
+ d.coeff[out+16] = int16((a3 + a2) >> 3)
+ d.coeff[out+32] = int16((a0 - a1) >> 3)
+ d.coeff[out+48] = int16((a3 - a2) >> 3)
+ out += 64
+ }
+}
diff --git a/vp8/partition.go b/vp8/partition.go
new file mode 100644
index 0000000..a69bd65
--- /dev/null
+++ b/vp8/partition.go
@@ -0,0 +1,127 @@
+// Copyright 2011 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 vp8
+
+// Each VP8 frame consists of between 2 and 9 bitstream partitions.
+// Each partition is byte-aligned and is independently arithmetic-encoded.
+//
+// This file implements decoding a partition's bitstream, as specified in
+// chapter 7. The implementation follows libwebp's approach instead of the
+// specification's reference C implementation. For example, we use a look-up
+// table instead of a for loop to recalibrate the encoded range.
+
+var (
+ lutShift = [127]uint8{
+ 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
+ 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+ 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+ 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+ }
+ lutRangeM1 = [127]uint8{
+ 127,
+ 127, 191,
+ 127, 159, 191, 223,
+ 127, 143, 159, 175, 191, 207, 223, 239,
+ 127, 135, 143, 151, 159, 167, 175, 183, 191, 199, 207, 215, 223, 231, 239, 247,
+ 127, 131, 135, 139, 143, 147, 151, 155, 159, 163, 167, 171, 175, 179, 183, 187,
+ 191, 195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239, 243, 247, 251,
+ 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157,
+ 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179, 181, 183, 185, 187, 189,
+ 191, 193, 195, 197, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217, 219, 221,
+ 223, 225, 227, 229, 231, 233, 235, 237, 239, 241, 243, 245, 247, 249, 251, 253,
+ }
+)
+
+// uniformProb represents a 50% probability that the next bit is 0.
+const uniformProb = 128
+
+// partition holds arithmetic-coded bits.
+type partition struct {
+ // buf is the input bytes.
+ buf []byte
+ // r is how many of buf's bytes have been consumed.
+ r int
+ // rangeM1 is range minus 1, where range is in the arithmetic coding sense,
+ // not the Go language sense.
+ rangeM1 uint32
+ // bits and nBits hold those bits shifted out of buf but not yet consumed.
+ bits uint32
+ nBits uint8
+ // unexpectedEOF tells whether we tried to read past buf.
+ unexpectedEOF bool
+}
+
+// init initializes the partition.
+func (p *partition) init(buf []byte) {
+ p.buf = buf
+ p.r = 0
+ p.rangeM1 = 254
+ p.bits = 0
+ p.nBits = 0
+ p.unexpectedEOF = false
+}
+
+// readBit returns the next bit.
+func (p *partition) readBit(prob uint8) bool {
+ if p.nBits < 8 {
+ if p.r >= len(p.buf) {
+ p.unexpectedEOF = true
+ return false
+ }
+ p.bits |= uint32(p.buf[p.r]) << (8 - p.nBits)
+ p.r++
+ p.nBits += 8
+ }
+ split := (p.rangeM1*uint32(prob))>>8 + 1
+ bit := p.bits >= split<<8
+ if bit {
+ p.rangeM1 -= split
+ p.bits -= split << 8
+ } else {
+ p.rangeM1 = split - 1
+ }
+ if p.rangeM1 < 127 {
+ shift := lutShift[p.rangeM1]
+ p.rangeM1 = uint32(lutRangeM1[p.rangeM1])
+ p.bits <<= shift
+ p.nBits -= shift
+ }
+ return bit
+}
+
+// readUint returns the next n-bit unsigned integer.
+func (p *partition) readUint(prob, n uint8) uint32 {
+ var u uint32
+ for n > 0 {
+ n--
+ if p.readBit(prob) {
+ u |= 1 << n
+ }
+ }
+ return u
+}
+
+// readInt returns the next n-bit signed integer.
+func (p *partition) readInt(prob, n uint8) int32 {
+ u := p.readUint(prob, n)
+ b := p.readBit(prob)
+ if b {
+ return -int32(u)
+ }
+ return int32(u)
+}
+
+// readOptionalInt returns the next n-bit signed integer in an encoding
+// where the likely result is zero.
+func (p *partition) readOptionalInt(prob, n uint8) int32 {
+ if !p.readBit(prob) {
+ return 0
+ }
+ return p.readInt(prob, n)
+}
diff --git a/vp8/pred.go b/vp8/pred.go
new file mode 100644
index 0000000..58c2689
--- /dev/null
+++ b/vp8/pred.go
@@ -0,0 +1,201 @@
+// Copyright 2011 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 vp8
+
+// This file implements parsing the predictor modes, as specified in chapter
+// 11.
+
+func (d *Decoder) parsePredModeY16(mbx int) {
+ var p uint8
+ if !d.fp.readBit(156) {
+ if !d.fp.readBit(163) {
+ p = predDC
+ } else {
+ p = predVE
+ }
+ } else if !d.fp.readBit(128) {
+ p = predHE
+ } else {
+ p = predTM
+ }
+ for i := 0; i < 4; i++ {
+ d.upMB[mbx].pred[i] = p
+ d.leftMB.pred[i] = p
+ }
+ d.predY16 = p
+}
+
+func (d *Decoder) parsePredModeC8() {
+ if !d.fp.readBit(142) {
+ d.predC8 = predDC
+ } else if !d.fp.readBit(114) {
+ d.predC8 = predVE
+ } else if !d.fp.readBit(183) {
+ d.predC8 = predHE
+ } else {
+ d.predC8 = predTM
+ }
+}
+
+func (d *Decoder) parsePredModeY4(mbx int) {
+ for j := 0; j < 4; j++ {
+ p := d.leftMB.pred[j]
+ for i := 0; i < 4; i++ {
+ prob := &predProb[d.upMB[mbx].pred[i]][p]
+ if !d.fp.readBit(prob[0]) {
+ p = predDC
+ } else if !d.fp.readBit(prob[1]) {
+ p = predTM
+ } else if !d.fp.readBit(prob[2]) {
+ p = predVE
+ } else if !d.fp.readBit(prob[3]) {
+ if !d.fp.readBit(prob[4]) {
+ p = predHE
+ } else if !d.fp.readBit(prob[5]) {
+ p = predRD
+ } else {
+ p = predVR
+ }
+ } else if !d.fp.readBit(prob[6]) {
+ p = predLD
+ } else if !d.fp.readBit(prob[7]) {
+ p = predVL
+ } else if !d.fp.readBit(prob[8]) {
+ p = predHD
+ } else {
+ p = predHU
+ }
+ d.predY4[j][i] = p
+ d.upMB[mbx].pred[i] = p
+ }
+ d.leftMB.pred[j] = p
+ }
+}
+
+// predProb are the probabilities to decode a 4x4 region's predictor mode given
+// the predictor modes of the regions above and left of it.
+// These values are specified in section 11.5.
+var predProb = [nPred][nPred][9]uint8{
+ {
+ {231, 120, 48, 89, 115, 113, 120, 152, 112},
+ {152, 179, 64, 126, 170, 118, 46, 70, 95},
+ {175, 69, 143, 80, 85, 82, 72, 155, 103},
+ {56, 58, 10, 171, 218, 189, 17, 13, 152},
+ {114, 26, 17, 163, 44, 195, 21, 10, 173},
+ {121, 24, 80, 195, 26, 62, 44, 64, 85},
+ {144, 71, 10, 38, 171, 213, 144, 34, 26},
+ {170, 46, 55, 19, 136, 160, 33, 206, 71},
+ {63, 20, 8, 114, 114, 208, 12, 9, 226},
+ {81, 40, 11, 96, 182, 84, 29, 16, 36},
+ },
+ {
+ {134, 183, 89, 137, 98, 101, 106, 165, 148},
+ {72, 187, 100, 130, 157, 111, 32, 75, 80},
+ {66, 102, 167, 99, 74, 62, 40, 234, 128},
+ {41, 53, 9, 178, 241, 141, 26, 8, 107},
+ {74, 43, 26, 146, 73, 166, 49, 23, 157},
+ {65, 38, 105, 160, 51, 52, 31, 115, 128},
+ {104, 79, 12, 27, 217, 255, 87, 17, 7},
+ {87, 68, 71, 44, 114, 51, 15, 186, 23},
+ {47, 41, 14, 110, 182, 183, 21, 17, 194},
+ {66, 45, 25, 102, 197, 189, 23, 18, 22},
+ },
+ {
+ {88, 88, 147, 150, 42, 46, 45, 196, 205},
+ {43, 97, 183, 117, 85, 38, 35, 179, 61},
+ {39, 53, 200, 87, 26, 21, 43, 232, 171},
+ {56, 34, 51, 104, 114, 102, 29, 93, 77},
+ {39, 28, 85, 171, 58, 165, 90, 98, 64},
+ {34, 22, 116, 206, 23, 34, 43, 166, 73},
+ {107, 54, 32, 26, 51, 1, 81, 43, 31},
+ {68, 25, 106, 22, 64, 171, 36, 225, 114},
+ {34, 19, 21, 102, 132, 188, 16, 76, 124},
+ {62, 18, 78, 95, 85, 57, 50, 48, 51},
+ },
+ {
+ {193, 101, 35, 159, 215, 111, 89, 46, 111},
+ {60, 148, 31, 172, 219, 228, 21, 18, 111},
+ {112, 113, 77, 85, 179, 255, 38, 120, 114},
+ {40, 42, 1, 196, 245, 209, 10, 25, 109},
+ {88, 43, 29, 140, 166, 213, 37, 43, 154},
+ {61, 63, 30, 155, 67, 45, 68, 1, 209},
+ {100, 80, 8, 43, 154, 1, 51, 26, 71},
+ {142, 78, 78, 16, 255, 128, 34, 197, 171},
+ {41, 40, 5, 102, 211, 183, 4, 1, 221},
+ {51, 50, 17, 168, 209, 192, 23, 25, 82},
+ },
+ {
+ {138, 31, 36, 171, 27, 166, 38, 44, 229},
+ {67, 87, 58, 169, 82, 115, 26, 59, 179},
+ {63, 59, 90, 180, 59, 166, 93, 73, 154},
+ {40, 40, 21, 116, 143, 209, 34, 39, 175},
+ {47, 15, 16, 183, 34, 223, 49, 45, 183},
+ {46, 17, 33, 183, 6, 98, 15, 32, 183},
+ {57, 46, 22, 24, 128, 1, 54, 17, 37},
+ {65, 32, 73, 115, 28, 128, 23, 128, 205},
+ {40, 3, 9, 115, 51, 192, 18, 6, 223},
+ {87, 37, 9, 115, 59, 77, 64, 21, 47},
+ },
+ {
+ {104, 55, 44, 218, 9, 54, 53, 130, 226},
+ {64, 90, 70, 205, 40, 41, 23, 26, 57},
+ {54, 57, 112, 184, 5, 41, 38, 166, 213},
+ {30, 34, 26, 133, 152, 116, 10, 32, 134},
+ {39, 19, 53, 221, 26, 114, 32, 73, 255},
+ {31, 9, 65, 234, 2, 15, 1, 118, 73},
+ {75, 32, 12, 51, 192, 255, 160, 43, 51},
+ {88, 31, 35, 67, 102, 85, 55, 186, 85},
+ {56, 21, 23, 111, 59, 205, 45, 37, 192},
+ {55, 38, 70, 124, 73, 102, 1, 34, 98},
+ },
+ {
+ {125, 98, 42, 88, 104, 85, 117, 175, 82},
+ {95, 84, 53, 89, 128, 100, 113, 101, 45},
+ {75, 79, 123, 47, 51, 128, 81, 171, 1},
+ {57, 17, 5, 71, 102, 57, 53, 41, 49},
+ {38, 33, 13, 121, 57, 73, 26, 1, 85},
+ {41, 10, 67, 138, 77, 110, 90, 47, 114},
+ {115, 21, 2, 10, 102, 255, 166, 23, 6},
+ {101, 29, 16, 10, 85, 128, 101, 196, 26},
+ {57, 18, 10, 102, 102, 213, 34, 20, 43},
+ {117, 20, 15, 36, 163, 128, 68, 1, 26},
+ },
+ {
+ {102, 61, 71, 37, 34, 53, 31, 243, 192},
+ {69, 60, 71, 38, 73, 119, 28, 222, 37},
+ {68, 45, 128, 34, 1, 47, 11, 245, 171},
+ {62, 17, 19, 70, 146, 85, 55, 62, 70},
+ {37, 43, 37, 154, 100, 163, 85, 160, 1},
+ {63, 9, 92, 136, 28, 64, 32, 201, 85},
+ {75, 15, 9, 9, 64, 255, 184, 119, 16},
+ {86, 6, 28, 5, 64, 255, 25, 248, 1},
+ {56, 8, 17, 132, 137, 255, 55, 116, 128},
+ {58, 15, 20, 82, 135, 57, 26, 121, 40},
+ },
+ {
+ {164, 50, 31, 137, 154, 133, 25, 35, 218},
+ {51, 103, 44, 131, 131, 123, 31, 6, 158},
+ {86, 40, 64, 135, 148, 224, 45, 183, 128},
+ {22, 26, 17, 131, 240, 154, 14, 1, 209},
+ {45, 16, 21, 91, 64, 222, 7, 1, 197},
+ {56, 21, 39, 155, 60, 138, 23, 102, 213},
+ {83, 12, 13, 54, 192, 255, 68, 47, 28},
+ {85, 26, 85, 85, 128, 128, 32, 146, 171},
+ {18, 11, 7, 63, 144, 171, 4, 4, 246},
+ {35, 27, 10, 146, 174, 171, 12, 26, 128},
+ },
+ {
+ {190, 80, 35, 99, 180, 80, 126, 54, 45},
+ {85, 126, 47, 87, 176, 51, 41, 20, 32},
+ {101, 75, 128, 139, 118, 146, 116, 128, 85},
+ {56, 41, 15, 176, 236, 85, 37, 9, 62},
+ {71, 30, 17, 119, 118, 255, 17, 18, 138},
+ {101, 38, 60, 138, 55, 70, 43, 26, 142},
+ {146, 36, 19, 30, 171, 255, 97, 27, 20},
+ {138, 45, 61, 62, 219, 1, 81, 188, 64},
+ {32, 41, 20, 117, 151, 142, 20, 21, 163},
+ {112, 19, 12, 61, 195, 128, 48, 4, 24},
+ },
+}
diff --git a/vp8/predfunc.go b/vp8/predfunc.go
new file mode 100644
index 0000000..f899958
--- /dev/null
+++ b/vp8/predfunc.go
@@ -0,0 +1,553 @@
+// Copyright 2011 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 vp8
+
+// This file implements the predicition functions, as specified in chapter 12.
+//
+// For each macroblock (of 1x16x16 luma and 2x8x8 chroma coefficients), the
+// luma values are either predicted as one large 16x16 region or 16 separate
+// 4x4 regions. The chroma values are always predicted as one 8x8 region.
+//
+// For 4x4 regions, the target block's predicted values (Xs) are a function of
+// its previously-decoded top and left border values, as well as a number of
+// pixels from the top-right:
+//
+// a b c d e f g h
+// p X X X X
+// q X X X X
+// r X X X X
+// s X X X X
+//
+// The predictor modes are:
+// - DC: all Xs = (b + c + d + e + p + q + r + s + 4) / 8.
+// - TM: the first X = (b + p - a), the second X = (c + p - a), and so on.
+// - VE: each X = the weighted average of its column's top value and that
+// value's neighbors, i.e. averages of abc, bcd, cde or def.
+// - HE: similar to VE except rows instead of columns, and the final row is
+// an average of r, s and s.
+// - RD, VR, LD, VL, HD, HU: these diagonal modes ("Right Down", "Vertical
+// Right", etc) are more complicated and are described in section 12.3.
+// All Xs are clipped to the range [0, 255].
+//
+// For 8x8 and 16x16 regions, the target block's predicted values are a
+// function of the top and left border values without the top-right overhang,
+// i.e. without the 8x8 or 16x16 equivalent of f, g and h. Furthermore:
+// - There are no diagonal predictor modes, only DC, TM, VE and HE.
+// - The DC mode has variants for macroblocks in the top row and/or left
+// column, i.e. for macroblocks with mby == 0 || mbx == 0.
+// - The VE and HE modes take only the column top or row left values; they do
+// not smooth that top/left value with its neighbors.
+
+// nPred is the number of predictor modes, not including the Top/Left versions
+// of the DC predictor mode.
+const nPred = 10
+
+const (
+ predDC = iota
+ predTM
+ predVE
+ predHE
+ predRD
+ predVR
+ predLD
+ predVL
+ predHD
+ predHU
+ predDCTop
+ predDCLeft
+ predDCTopLeft
+)
+
+func checkTopLeftPred(mbx, mby int, p uint8) uint8 {
+ if p != predDC {
+ return p
+ }
+ if mbx == 0 {
+ if mby == 0 {
+ return predDCTopLeft
+ }
+ return predDCLeft
+ }
+ if mby == 0 {
+ return predDCTop
+ }
+ return predDC
+}
+
+var predFunc4 = [...]func(*Decoder, int, int){
+ predFunc4DC,
+ predFunc4TM,
+ predFunc4VE,
+ predFunc4HE,
+ predFunc4RD,
+ predFunc4VR,
+ predFunc4LD,
+ predFunc4VL,
+ predFunc4HD,
+ predFunc4HU,
+ nil,
+ nil,
+ nil,
+}
+
+var predFunc8 = [...]func(*Decoder, int, int){
+ predFunc8DC,
+ predFunc8TM,
+ predFunc8VE,
+ predFunc8HE,
+ nil,
+ nil,
+ nil,
+ nil,
+ nil,
+ nil,
+ predFunc8DCTop,
+ predFunc8DCLeft,
+ predFunc8DCTopLeft,
+}
+
+var predFunc16 = [...]func(*Decoder, int, int){
+ predFunc16DC,
+ predFunc16TM,
+ predFunc16VE,
+ predFunc16HE,
+ nil,
+ nil,
+ nil,
+ nil,
+ nil,
+ nil,
+ predFunc16DCTop,
+ predFunc16DCLeft,
+ predFunc16DCTopLeft,
+}
+
+func predFunc4DC(z *Decoder, y, x int) {
+ sum := uint32(4)
+ for i := 0; i < 4; i++ {
+ sum += uint32(z.ybr[y-1][x+i])
+ }
+ for j := 0; j < 4; j++ {
+ sum += uint32(z.ybr[y+j][x-1])
+ }
+ avg := uint8(sum / 8)
+ for j := 0; j < 4; j++ {
+ for i := 0; i < 4; i++ {
+ z.ybr[y+j][x+i] = avg
+ }
+ }
+}
+
+func predFunc4TM(z *Decoder, y, x int) {
+ delta0 := -int32(z.ybr[y-1][x-1])
+ for j := 0; j < 4; j++ {
+ delta1 := delta0 + int32(z.ybr[y+j][x-1])
+ for i := 0; i < 4; i++ {
+ delta2 := delta1 + int32(z.ybr[y-1][x+i])
+ z.ybr[y+j][x+i] = uint8(clip(delta2, 0, 255))
+ }
+ }
+}
+
+func predFunc4VE(z *Decoder, y, x int) {
+ a := int32(z.ybr[y-1][x-1])
+ b := int32(z.ybr[y-1][x+0])
+ c := int32(z.ybr[y-1][x+1])
+ d := int32(z.ybr[y-1][x+2])
+ e := int32(z.ybr[y-1][x+3])
+ f := int32(z.ybr[y-1][x+4])
+ abc := uint8((a + 2*b + c + 2) / 4)
+ bcd := uint8((b + 2*c + d + 2) / 4)
+ cde := uint8((c + 2*d + e + 2) / 4)
+ def := uint8((d + 2*e + f + 2) / 4)
+ for j := 0; j < 4; j++ {
+ z.ybr[y+j][x+0] = abc
+ z.ybr[y+j][x+1] = bcd
+ z.ybr[y+j][x+2] = cde
+ z.ybr[y+j][x+3] = def
+ }
+}
+
+func predFunc4HE(z *Decoder, y, x int) {
+ s := int32(z.ybr[y+3][x-1])
+ r := int32(z.ybr[y+2][x-1])
+ q := int32(z.ybr[y+1][x-1])
+ p := int32(z.ybr[y+0][x-1])
+ a := int32(z.ybr[y-1][x-1])
+ ssr := uint8((s + 2*s + r + 2) / 4)
+ srq := uint8((s + 2*r + q + 2) / 4)
+ rqp := uint8((r + 2*q + p + 2) / 4)
+ apq := uint8((a + 2*p + q + 2) / 4)
+ for i := 0; i < 4; i++ {
+ z.ybr[y+0][x+i] = apq
+ z.ybr[y+1][x+i] = rqp
+ z.ybr[y+2][x+i] = srq
+ z.ybr[y+3][x+i] = ssr
+ }
+}
+
+func predFunc4RD(z *Decoder, y, x int) {
+ s := int32(z.ybr[y+3][x-1])
+ r := int32(z.ybr[y+2][x-1])
+ q := int32(z.ybr[y+1][x-1])
+ p := int32(z.ybr[y+0][x-1])
+ a := int32(z.ybr[y-1][x-1])
+ b := int32(z.ybr[y-1][x+0])
+ c := int32(z.ybr[y-1][x+1])
+ d := int32(z.ybr[y-1][x+2])
+ e := int32(z.ybr[y-1][x+3])
+ srq := uint8((s + 2*r + q + 2) / 4)
+ rqp := uint8((r + 2*q + p + 2) / 4)
+ qpa := uint8((q + 2*p + a + 2) / 4)
+ pab := uint8((p + 2*a + b + 2) / 4)
+ abc := uint8((a + 2*b + c + 2) / 4)
+ bcd := uint8((b + 2*c + d + 2) / 4)
+ cde := uint8((c + 2*d + e + 2) / 4)
+ z.ybr[y+0][x+0] = pab
+ z.ybr[y+0][x+1] = abc
+ z.ybr[y+0][x+2] = bcd
+ z.ybr[y+0][x+3] = cde
+ z.ybr[y+1][x+0] = qpa
+ z.ybr[y+1][x+1] = pab
+ z.ybr[y+1][x+2] = abc
+ z.ybr[y+1][x+3] = bcd
+ z.ybr[y+2][x+0] = rqp
+ z.ybr[y+2][x+1] = qpa
+ z.ybr[y+2][x+2] = pab
+ z.ybr[y+2][x+3] = abc
+ z.ybr[y+3][x+0] = srq
+ z.ybr[y+3][x+1] = rqp
+ z.ybr[y+3][x+2] = qpa
+ z.ybr[y+3][x+3] = pab
+}
+
+func predFunc4VR(z *Decoder, y, x int) {
+ r := int32(z.ybr[y+2][x-1])
+ q := int32(z.ybr[y+1][x-1])
+ p := int32(z.ybr[y+0][x-1])
+ a := int32(z.ybr[y-1][x-1])
+ b := int32(z.ybr[y-1][x+0])
+ c := int32(z.ybr[y-1][x+1])
+ d := int32(z.ybr[y-1][x+2])
+ e := int32(z.ybr[y-1][x+3])
+ ab := uint8((a + b + 1) / 2)
+ bc := uint8((b + c + 1) / 2)
+ cd := uint8((c + d + 1) / 2)
+ de := uint8((d + e + 1) / 2)
+ rqp := uint8((r + 2*q + p + 2) / 4)
+ qpa := uint8((q + 2*p + a + 2) / 4)
+ pab := uint8((p + 2*a + b + 2) / 4)
+ abc := uint8((a + 2*b + c + 2) / 4)
+ bcd := uint8((b + 2*c + d + 2) / 4)
+ cde := uint8((c + 2*d + e + 2) / 4)
+ z.ybr[y+0][x+0] = ab
+ z.ybr[y+0][x+1] = bc
+ z.ybr[y+0][x+2] = cd
+ z.ybr[y+0][x+3] = de
+ z.ybr[y+1][x+0] = pab
+ z.ybr[y+1][x+1] = abc
+ z.ybr[y+1][x+2] = bcd
+ z.ybr[y+1][x+3] = cde
+ z.ybr[y+2][x+0] = qpa
+ z.ybr[y+2][x+1] = ab
+ z.ybr[y+2][x+2] = bc
+ z.ybr[y+2][x+3] = cd
+ z.ybr[y+3][x+0] = rqp
+ z.ybr[y+3][x+1] = pab
+ z.ybr[y+3][x+2] = abc
+ z.ybr[y+3][x+3] = bcd
+}
+
+func predFunc4LD(z *Decoder, y, x int) {
+ a := int32(z.ybr[y-1][x+0])
+ b := int32(z.ybr[y-1][x+1])
+ c := int32(z.ybr[y-1][x+2])
+ d := int32(z.ybr[y-1][x+3])
+ e := int32(z.ybr[y-1][x+4])
+ f := int32(z.ybr[y-1][x+5])
+ g := int32(z.ybr[y-1][x+6])
+ h := int32(z.ybr[y-1][x+7])
+ abc := uint8((a + 2*b + c + 2) / 4)
+ bcd := uint8((b + 2*c + d + 2) / 4)
+ cde := uint8((c + 2*d + e + 2) / 4)
+ def := uint8((d + 2*e + f + 2) / 4)
+ efg := uint8((e + 2*f + g + 2) / 4)
+ fgh := uint8((f + 2*g + h + 2) / 4)
+ ghh := uint8((g + 2*h + h + 2) / 4)
+ z.ybr[y+0][x+0] = abc
+ z.ybr[y+0][x+1] = bcd
+ z.ybr[y+0][x+2] = cde
+ z.ybr[y+0][x+3] = def
+ z.ybr[y+1][x+0] = bcd
+ z.ybr[y+1][x+1] = cde
+ z.ybr[y+1][x+2] = def
+ z.ybr[y+1][x+3] = efg
+ z.ybr[y+2][x+0] = cde
+ z.ybr[y+2][x+1] = def
+ z.ybr[y+2][x+2] = efg
+ z.ybr[y+2][x+3] = fgh
+ z.ybr[y+3][x+0] = def
+ z.ybr[y+3][x+1] = efg
+ z.ybr[y+3][x+2] = fgh
+ z.ybr[y+3][x+3] = ghh
+}
+
+func predFunc4VL(z *Decoder, y, x int) {
+ a := int32(z.ybr[y-1][x+0])
+ b := int32(z.ybr[y-1][x+1])
+ c := int32(z.ybr[y-1][x+2])
+ d := int32(z.ybr[y-1][x+3])
+ e := int32(z.ybr[y-1][x+4])
+ f := int32(z.ybr[y-1][x+5])
+ g := int32(z.ybr[y-1][x+6])
+ h := int32(z.ybr[y-1][x+7])
+ ab := uint8((a + b + 1) / 2)
+ bc := uint8((b + c + 1) / 2)
+ cd := uint8((c + d + 1) / 2)
+ de := uint8((d + e + 1) / 2)
+ abc := uint8((a + 2*b + c + 2) / 4)
+ bcd := uint8((b + 2*c + d + 2) / 4)
+ cde := uint8((c + 2*d + e + 2) / 4)
+ def := uint8((d + 2*e + f + 2) / 4)
+ efg := uint8((e + 2*f + g + 2) / 4)
+ fgh := uint8((f + 2*g + h + 2) / 4)
+ z.ybr[y+0][x+0] = ab
+ z.ybr[y+0][x+1] = bc
+ z.ybr[y+0][x+2] = cd
+ z.ybr[y+0][x+3] = de
+ z.ybr[y+1][x+0] = abc
+ z.ybr[y+1][x+1] = bcd
+ z.ybr[y+1][x+2] = cde
+ z.ybr[y+1][x+3] = def
+ z.ybr[y+2][x+0] = bc
+ z.ybr[y+2][x+1] = cd
+ z.ybr[y+2][x+2] = de
+ z.ybr[y+2][x+3] = efg
+ z.ybr[y+3][x+0] = bcd
+ z.ybr[y+3][x+1] = cde
+ z.ybr[y+3][x+2] = def
+ z.ybr[y+3][x+3] = fgh
+}
+
+func predFunc4HD(z *Decoder, y, x int) {
+ s := int32(z.ybr[y+3][x-1])
+ r := int32(z.ybr[y+2][x-1])
+ q := int32(z.ybr[y+1][x-1])
+ p := int32(z.ybr[y+0][x-1])
+ a := int32(z.ybr[y-1][x-1])
+ b := int32(z.ybr[y-1][x+0])
+ c := int32(z.ybr[y-1][x+1])
+ d := int32(z.ybr[y-1][x+2])
+ sr := uint8((s + r + 1) / 2)
+ rq := uint8((r + q + 1) / 2)
+ qp := uint8((q + p + 1) / 2)
+ pa := uint8((p + a + 1) / 2)
+ srq := uint8((s + 2*r + q + 2) / 4)
+ rqp := uint8((r + 2*q + p + 2) / 4)
+ qpa := uint8((q + 2*p + a + 2) / 4)
+ pab := uint8((p + 2*a + b + 2) / 4)
+ abc := uint8((a + 2*b + c + 2) / 4)
+ bcd := uint8((b + 2*c + d + 2) / 4)
+ z.ybr[y+0][x+0] = pa
+ z.ybr[y+0][x+1] = pab
+ z.ybr[y+0][x+2] = abc
+ z.ybr[y+0][x+3] = bcd
+ z.ybr[y+1][x+0] = qp
+ z.ybr[y+1][x+1] = qpa
+ z.ybr[y+1][x+2] = pa
+ z.ybr[y+1][x+3] = pab
+ z.ybr[y+2][x+0] = rq
+ z.ybr[y+2][x+1] = rqp
+ z.ybr[y+2][x+2] = qp
+ z.ybr[y+2][x+3] = qpa
+ z.ybr[y+3][x+0] = sr
+ z.ybr[y+3][x+1] = srq
+ z.ybr[y+3][x+2] = rq
+ z.ybr[y+3][x+3] = rqp
+}
+
+func predFunc4HU(z *Decoder, y, x int) {
+ s := int32(z.ybr[y+3][x-1])
+ r := int32(z.ybr[y+2][x-1])
+ q := int32(z.ybr[y+1][x-1])
+ p := int32(z.ybr[y+0][x-1])
+ pq := uint8((p + q + 1) / 2)
+ qr := uint8((q + r + 1) / 2)
+ rs := uint8((r + s + 1) / 2)
+ pqr := uint8((p + 2*q + r + 2) / 4)
+ qrs := uint8((q + 2*r + s + 2) / 4)
+ rss := uint8((r + 2*s + s + 2) / 4)
+ sss := uint8(s)
+ z.ybr[y+0][x+0] = pq
+ z.ybr[y+0][x+1] = pqr
+ z.ybr[y+0][x+2] = qr
+ z.ybr[y+0][x+3] = qrs
+ z.ybr[y+1][x+0] = qr
+ z.ybr[y+1][x+1] = qrs
+ z.ybr[y+1][x+2] = rs
+ z.ybr[y+1][x+3] = rss
+ z.ybr[y+2][x+0] = rs
+ z.ybr[y+2][x+1] = rss
+ z.ybr[y+2][x+2] = sss
+ z.ybr[y+2][x+3] = sss
+ z.ybr[y+3][x+0] = sss
+ z.ybr[y+3][x+1] = sss
+ z.ybr[y+3][x+2] = sss
+ z.ybr[y+3][x+3] = sss
+}
+
+func predFunc8DC(z *Decoder, y, x int) {
+ sum := uint32(8)
+ for i := 0; i < 8; i++ {
+ sum += uint32(z.ybr[y-1][x+i])
+ }
+ for j := 0; j < 8; j++ {
+ sum += uint32(z.ybr[y+j][x-1])
+ }
+ avg := uint8(sum / 16)
+ for j := 0; j < 8; j++ {
+ for i := 0; i < 8; i++ {
+ z.ybr[y+j][x+i] = avg
+ }
+ }
+}
+
+func predFunc8TM(z *Decoder, y, x int) {
+ delta0 := -int32(z.ybr[y-1][x-1])
+ for j := 0; j < 8; j++ {
+ delta1 := delta0 + int32(z.ybr[y+j][x-1])
+ for i := 0; i < 8; i++ {
+ delta2 := delta1 + int32(z.ybr[y-1][x+i])
+ z.ybr[y+j][x+i] = uint8(clip(delta2, 0, 255))
+ }
+ }
+}
+
+func predFunc8VE(z *Decoder, y, x int) {
+ for j := 0; j < 8; j++ {
+ for i := 0; i < 8; i++ {
+ z.ybr[y+j][x+i] = z.ybr[y-1][x+i]
+ }
+ }
+}
+
+func predFunc8HE(z *Decoder, y, x int) {
+ for j := 0; j < 8; j++ {
+ for i := 0; i < 8; i++ {
+ z.ybr[y+j][x+i] = z.ybr[y+j][x-1]
+ }
+ }
+}
+
+func predFunc8DCTop(z *Decoder, y, x int) {
+ sum := uint32(4)
+ for j := 0; j < 8; j++ {
+ sum += uint32(z.ybr[y+j][x-1])
+ }
+ avg := uint8(sum / 8)
+ for j := 0; j < 8; j++ {
+ for i := 0; i < 8; i++ {
+ z.ybr[y+j][x+i] = avg
+ }
+ }
+}
+
+func predFunc8DCLeft(z *Decoder, y, x int) {
+ sum := uint32(4)
+ for i := 0; i < 8; i++ {
+ sum += uint32(z.ybr[y-1][x+i])
+ }
+ avg := uint8(sum / 8)
+ for j := 0; j < 8; j++ {
+ for i := 0; i < 8; i++ {
+ z.ybr[y+j][x+i] = avg
+ }
+ }
+}
+
+func predFunc8DCTopLeft(z *Decoder, y, x int) {
+ for j := 0; j < 8; j++ {
+ for i := 0; i < 8; i++ {
+ z.ybr[y+j][x+i] = 0x80
+ }
+ }
+}
+
+func predFunc16DC(z *Decoder, y, x int) {
+ sum := uint32(16)
+ for i := 0; i < 16; i++ {
+ sum += uint32(z.ybr[y-1][x+i])
+ }
+ for j := 0; j < 16; j++ {
+ sum += uint32(z.ybr[y+j][x-1])
+ }
+ avg := uint8(sum / 32)
+ for j := 0; j < 16; j++ {
+ for i := 0; i < 16; i++ {
+ z.ybr[y+j][x+i] = avg
+ }
+ }
+}
+
+func predFunc16TM(z *Decoder, y, x int) {
+ delta0 := -int32(z.ybr[y-1][x-1])
+ for j := 0; j < 16; j++ {
+ delta1 := delta0 + int32(z.ybr[y+j][x-1])
+ for i := 0; i < 16; i++ {
+ delta2 := delta1 + int32(z.ybr[y-1][x+i])
+ z.ybr[y+j][x+i] = uint8(clip(delta2, 0, 255))
+ }
+ }
+}
+
+func predFunc16VE(z *Decoder, y, x int) {
+ for j := 0; j < 16; j++ {
+ for i := 0; i < 16; i++ {
+ z.ybr[y+j][x+i] = z.ybr[y-1][x+i]
+ }
+ }
+}
+
+func predFunc16HE(z *Decoder, y, x int) {
+ for j := 0; j < 16; j++ {
+ for i := 0; i < 16; i++ {
+ z.ybr[y+j][x+i] = z.ybr[y+j][x-1]
+ }
+ }
+}
+
+func predFunc16DCTop(z *Decoder, y, x int) {
+ sum := uint32(8)
+ for j := 0; j < 16; j++ {
+ sum += uint32(z.ybr[y+j][x-1])
+ }
+ avg := uint8(sum / 16)
+ for j := 0; j < 16; j++ {
+ for i := 0; i < 16; i++ {
+ z.ybr[y+j][x+i] = avg
+ }
+ }
+}
+
+func predFunc16DCLeft(z *Decoder, y, x int) {
+ sum := uint32(8)
+ for i := 0; i < 16; i++ {
+ sum += uint32(z.ybr[y-1][x+i])
+ }
+ avg := uint8(sum / 16)
+ for j := 0; j < 16; j++ {
+ for i := 0; i < 16; i++ {
+ z.ybr[y+j][x+i] = avg
+ }
+ }
+}
+
+func predFunc16DCTopLeft(z *Decoder, y, x int) {
+ for j := 0; j < 16; j++ {
+ for i := 0; i < 16; i++ {
+ z.ybr[y+j][x+i] = 0x80
+ }
+ }
+}
diff --git a/vp8/quant.go b/vp8/quant.go
new file mode 100644
index 0000000..8bf12a0
--- /dev/null
+++ b/vp8/quant.go
@@ -0,0 +1,95 @@
+// Copyright 2011 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 vp8
+
+// This file implements parsing the quantization factors.
+
+// quant are DC/AC quantization factors.
+type quant struct {
+ y1 [2]uint16
+ y2 [2]uint16
+ uv [2]uint16
+}
+
+// clip clips x to the range [min, max] inclusive.
+func clip(x, min, max int32) int32 {
+ if x < min {
+ return min
+ }
+ if x > max {
+ return max
+ }
+ return x
+}
+
+// parseQuant parses the quantization factors, as specified in section 9.6.
+func (d *Decoder) parseQuant() {
+ baseQ0 := d.fp.readUint(uniformProb, 7)
+ dqy1DC := d.fp.readOptionalInt(uniformProb, 4)
+ const dqy1AC = 0
+ dqy2DC := d.fp.readOptionalInt(uniformProb, 4)
+ dqy2AC := d.fp.readOptionalInt(uniformProb, 4)
+ dquvDC := d.fp.readOptionalInt(uniformProb, 4)
+ dquvAC := d.fp.readOptionalInt(uniformProb, 4)
+ for i := 0; i < nSegment; i++ {
+ q := int32(baseQ0)
+ if d.segmentHeader.useSegment {
+ if d.segmentHeader.relativeDelta {
+ q += int32(d.segmentHeader.quantizer[i])
+ } else {
+ q = int32(d.segmentHeader.quantizer[i])
+ }
+ }
+ d.quant[i].y1[0] = dequantTableDC[clip(q+dqy1DC, 0, 127)]
+ d.quant[i].y1[1] = dequantTableAC[clip(q+dqy1AC, 0, 127)]
+ d.quant[i].y2[0] = dequantTableDC[clip(q+dqy2DC, 0, 127)] * 2
+ d.quant[i].y2[1] = dequantTableAC[clip(q+dqy2AC, 0, 127)] * 155 / 100
+ if d.quant[i].y2[1] < 8 {
+ d.quant[i].y2[1] = 8
+ }
+ d.quant[i].uv[0] = dequantTableDC[clip(q+dquvDC, 0, 127)]
+ d.quant[i].uv[1] = dequantTableAC[clip(q+dquvAC, 0, 127)]
+ }
+}
+
+// The dequantization tables are specified in section 14.1.
+var (
+ dequantTableDC = [128]uint16{
+ 4, 5, 6, 7, 8, 9, 10, 10,
+ 11, 12, 13, 14, 15, 16, 17, 17,
+ 18, 19, 20, 20, 21, 21, 22, 22,
+ 23, 23, 24, 25, 25, 26, 27, 28,
+ 29, 30, 31, 32, 33, 34, 35, 36,
+ 37, 37, 38, 39, 40, 41, 42, 43,
+ 44, 45, 46, 46, 47, 48, 49, 50,
+ 51, 52, 53, 54, 55, 56, 57, 58,
+ 59, 60, 61, 62, 63, 64, 65, 66,
+ 67, 68, 69, 70, 71, 72, 73, 74,
+ 75, 76, 76, 77, 78, 79, 80, 81,
+ 82, 83, 84, 85, 86, 87, 88, 89,
+ 91, 93, 95, 96, 98, 100, 101, 102,
+ 104, 106, 108, 110, 112, 114, 116, 118,
+ 122, 124, 126, 128, 130, 132, 134, 136,
+ 138, 140, 143, 145, 148, 151, 154, 157,
+ }
+ dequantTableAC = [128]uint16{
+ 4, 5, 6, 7, 8, 9, 10, 11,
+ 12, 13, 14, 15, 16, 17, 18, 19,
+ 20, 21, 22, 23, 24, 25, 26, 27,
+ 28, 29, 30, 31, 32, 33, 34, 35,
+ 36, 37, 38, 39, 40, 41, 42, 43,
+ 44, 45, 46, 47, 48, 49, 50, 51,
+ 52, 53, 54, 55, 56, 57, 58, 60,
+ 62, 64, 66, 68, 70, 72, 74, 76,
+ 78, 80, 82, 84, 86, 88, 90, 92,
+ 94, 96, 98, 100, 102, 104, 106, 108,
+ 110, 112, 114, 116, 119, 122, 125, 128,
+ 131, 134, 137, 140, 143, 146, 149, 152,
+ 155, 158, 161, 164, 167, 170, 173, 177,
+ 181, 185, 189, 193, 197, 201, 205, 209,
+ 213, 217, 221, 225, 229, 234, 239, 245,
+ 249, 254, 259, 264, 269, 274, 279, 284,
+ }
+)
diff --git a/vp8/reconstruct.go b/vp8/reconstruct.go
new file mode 100644
index 0000000..525e442
--- /dev/null
+++ b/vp8/reconstruct.go
@@ -0,0 +1,435 @@
+// Copyright 2011 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 vp8
+
+// This file implements decoding DCT/WHT residual coefficients and
+// reconstructing YCbCr data equal to predicted values plus residuals.
+//
+// There are 1*16*16 + 2*8*8 + 1*4*4 coefficients per macroblock:
+// - 1*16*16 luma DCT coefficients,
+// - 2*8*8 chroma DCT coefficients, and
+// - 1*4*4 luma WHT coefficients.
+// Coefficients are read in lots of 16, and the later coefficients in each lot
+// are often zero.
+//
+// The YCbCr data consists of 1*16*16 luma values and 2*8*8 chroma values,
+// plus previously decoded values along the top and left borders. The combined
+// values are laid out as a [1+16+1+8][32]uint8 so that vertically adjacent
+// samples are 32 bytes apart. In detail, the layout is:
+//
+// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// . . . . . . . a b b b b b b b b b b b b b b b b c c c c . . . . 0
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 1
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 2
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 3
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y c c c c . . . . 4
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 5
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 6
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 7
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y c c c c . . . . 8
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 9
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 10
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 11
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y c c c c . . . . 12
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 13
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 14
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 15
+// . . . . . . . d Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y . . . . . . . . 16
+// . . . . . . . e f f f f f f f f . . . . . . . g h h h h h h h h 17
+// . . . . . . . i B B B B B B B B . . . . . . . j R R R R R R R R 18
+// . . . . . . . i B B B B B B B B . . . . . . . j R R R R R R R R 19
+// . . . . . . . i B B B B B B B B . . . . . . . j R R R R R R R R 20
+// . . . . . . . i B B B B B B B B . . . . . . . j R R R R R R R R 21
+// . . . . . . . i B B B B B B B B . . . . . . . j R R R R R R R R 22
+// . . . . . . . i B B B B B B B B . . . . . . . j R R R R R R R R 23
+// . . . . . . . i B B B B B B B B . . . . . . . j R R R R R R R R 24
+// . . . . . . . i B B B B B B B B . . . . . . . j R R R R R R R R 25
+//
+// Y, B and R are the reconstructed luma (Y) and chroma (B, R) values.
+// The Y values are predicted (either as one 16x16 region or 16 4x4 regions)
+// based on the row above's Y values (some combination of {abc} or {dYC}) and
+// the column left's Y values (either {ad} or {bY}). Similarly, B and R values
+// are predicted on the row above and column left of their respective 8x8
+// region: {efi} for B, {ghj} for R.
+//
+// For uppermost macroblocks (i.e. those with mby == 0), the {abcefgh} values
+// are initialized to 0x81. Otherwise, they are copied from the bottom row of
+// the macroblock above. The {c} values are then duplicated from row 0 to rows
+// 4, 8 and 12 of the ybr workspace.
+// Similarly, for leftmost macroblocks (i.e. those with mbx == 0), the {adeigj}
+// values are initialized to 0x7f. Otherwise, they are copied from the right
+// column of the macroblock to the left.
+// For the top-left macroblock (with mby == 0 && mbx == 0), {aeg} is 0x81.
+//
+// When moving from one macroblock to the next horizontally, the {adeigj}
+// values can simply be copied from the workspace to itself, shifted by 8 or
+// 16 columns. When moving from one macroblock to the next vertically,
+// filtering can occur and hence the row values have to be copied from the
+// post-filtered image instead of the pre-filtered workspace.
+
+const (
+ bCoeffBase = 1*16*16 + 0*8*8
+ rCoeffBase = 1*16*16 + 1*8*8
+ whtCoeffBase = 1*16*16 + 2*8*8
+)
+
+const (
+ ybrYX = 8
+ ybrYY = 1
+ ybrBX = 8
+ ybrBY = 18
+ ybrRX = 24
+ ybrRY = 18
+)
+
+// prepareYBR prepares the {abcdefghij} elements of ybr.
+func (d *Decoder) prepareYBR(mbx, mby int) {
+ if mbx == 0 {
+ for y := 0; y < 17; y++ {
+ d.ybr[y][7] = 0x81
+ }
+ for y := 17; y < 26; y++ {
+ d.ybr[y][7] = 0x81
+ d.ybr[y][23] = 0x81
+ }
+ } else {
+ for y := 0; y < 17; y++ {
+ d.ybr[y][7] = d.ybr[y][7+16]
+ }
+ for y := 17; y < 26; y++ {
+ d.ybr[y][7] = d.ybr[y][15]
+ d.ybr[y][23] = d.ybr[y][31]
+ }
+ }
+ if mby == 0 {
+ for x := 7; x < 28; x++ {
+ d.ybr[0][x] = 0x7f
+ }
+ for x := 7; x < 16; x++ {
+ d.ybr[17][x] = 0x7f
+ }
+ for x := 23; x < 32; x++ {
+ d.ybr[17][x] = 0x7f
+ }
+ } else {
+ for i := 0; i < 16; i++ {
+ d.ybr[0][8+i] = d.img.Y[(16*mby-1)*d.img.YStride+16*mbx+i]
+ }
+ for i := 0; i < 8; i++ {
+ d.ybr[17][8+i] = d.img.Cb[(8*mby-1)*d.img.CStride+8*mbx+i]
+ }
+ for i := 0; i < 8; i++ {
+ d.ybr[17][24+i] = d.img.Cr[(8*mby-1)*d.img.CStride+8*mbx+i]
+ }
+ if mbx == d.mbw-1 {
+ for i := 16; i < 20; i++ {
+ d.ybr[0][8+i] = d.img.Y[(16*mby-1)*d.img.YStride+16*mbx+15]
+ }
+ } else {
+ for i := 16; i < 20; i++ {
+ d.ybr[0][8+i] = d.img.Y[(16*mby-1)*d.img.YStride+16*mbx+i]
+ }
+ }
+ }
+ for y := 4; y < 16; y += 4 {
+ d.ybr[y][24] = d.ybr[0][24]
+ d.ybr[y][25] = d.ybr[0][25]
+ d.ybr[y][26] = d.ybr[0][26]
+ d.ybr[y][27] = d.ybr[0][27]
+ }
+}
+
+// btou converts a bool to a 0/1 value.
+func btou(b bool) uint8 {
+ if b {
+ return 1
+ }
+ return 0
+}
+
+// pack packs four 0/1 values into four bits of a uint32.
+func pack(x [4]uint8, shift int) uint32 {
+ u := uint32(x[0])<<0 | uint32(x[1])<<1 | uint32(x[2])<<2 | uint32(x[3])<<3
+ return u << uint(shift)
+}
+
+// unpack unpacks four 0/1 values from a four-bit value.
+var unpack = [16][4]uint8{
+ {0, 0, 0, 0},
+ {1, 0, 0, 0},
+ {0, 1, 0, 0},
+ {1, 1, 0, 0},
+ {0, 0, 1, 0},
+ {1, 0, 1, 0},
+ {0, 1, 1, 0},
+ {1, 1, 1, 0},
+ {0, 0, 0, 1},
+ {1, 0, 0, 1},
+ {0, 1, 0, 1},
+ {1, 1, 0, 1},
+ {0, 0, 1, 1},
+ {1, 0, 1, 1},
+ {0, 1, 1, 1},
+ {1, 1, 1, 1},
+}
+
+var (
+ // The mapping from 4x4 region position to band is specified in section 13.3.
+ bands = [17]uint8{0, 1, 2, 3, 6, 4, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7, 0}
+ // Category probabilties are specified in section 13.2.
+ // Decoding categories 1 and 2 are done inline.
+ cat3456 = [4][12]uint8{
+ {173, 148, 140, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+ {176, 155, 140, 135, 0, 0, 0, 0, 0, 0, 0, 0},
+ {180, 157, 141, 134, 130, 0, 0, 0, 0, 0, 0, 0},
+ {254, 254, 243, 230, 196, 177, 153, 140, 133, 130, 129, 0},
+ }
+ // The zigzag order is:
+ // 0 1 5 6
+ // 2 4 7 12
+ // 3 8 11 13
+ // 9 10 14 15
+ zigzag = [16]uint8{0, 1, 4, 8, 5, 2, 3, 6, 9, 12, 13, 10, 7, 11, 14, 15}
+)
+
+// parseResiduals4 parses a 4x4 region of residual coefficients, as specified
+// in section 13.3, and returns a 0/1 value indicating whether there was at
+// least one non-zero coefficient.
+// r is the partition to read bits from.
+// plane and context describe which token probability table to use. context is
+// either 0, 1 or 2, and equals how many of the macroblock left and macroblock
+// above have non-zero coefficients.
+// quant are the DC/AC quantization factors.
+// skipFirstCoeff is whether the DC coefficient has already been parsed.
+// coeffBase is the base index of d.coeff to write to.
+func (d *Decoder) parseResiduals4(r *partition, plane int, context uint8, quant [2]uint16, skipFirstCoeff bool, coeffBase int) uint8 {
+ prob, n := &d.tokenProb[plane], 0
+ if skipFirstCoeff {
+ n = 1
+ }
+ p := prob[bands[n]][context]
+ if !r.readBit(p[0]) {
+ return 0
+ }
+ for n != 16 {
+ n++
+ if !r.readBit(p[1]) {
+ p = prob[bands[n]][0]
+ continue
+ }
+ var v uint32
+ if !r.readBit(p[2]) {
+ v = 1
+ p = prob[bands[n]][1]
+ } else {
+ if !r.readBit(p[3]) {
+ if !r.readBit(p[4]) {
+ v = 2
+ } else {
+ v = 3 + r.readUint(p[5], 1)
+ }
+ } else if !r.readBit(p[6]) {
+ if !r.readBit(p[7]) {
+ // Category 1.
+ v = 5 + r.readUint(159, 1)
+ } else {
+ // Category 2.
+ v = 7 + 2*r.readUint(165, 1) + r.readUint(145, 1)
+ }
+ } else {
+ // Categories 3, 4, 5 or 6.
+ b1 := r.readUint(p[8], 1)
+ b0 := r.readUint(p[9+b1], 1)
+ cat := 2*b1 + b0
+ tab := &cat3456[cat]
+ v = 0
+ for i := 0; tab[i] != 0; i++ {
+ v *= 2
+ v += r.readUint(tab[i], 1)
+ }
+ v += 3 + (8 << cat)
+ }
+ p = prob[bands[n]][2]
+ }
+ z := zigzag[n-1]
+ c := int32(v) * int32(quant[btou(z > 0)])
+ if r.readBit(uniformProb) {
+ c = -c
+ }
+ d.coeff[coeffBase+int(z)] = int16(c)
+ if n == 16 || !r.readBit(p[0]) {
+ return 1
+ }
+ }
+ return 1
+}
+
+// parseResiduals parses the residuals.
+func (d *Decoder) parseResiduals(mbx, mby int) {
+ partition := &d.op[mby&(d.nOP-1)]
+ plane := planeY1SansY2
+ quant := &d.quant[d.segment]
+
+ // Parse the DC coefficient of each 4x4 luma region.
+ if d.usePredY16 {
+ nz := d.parseResiduals4(partition, planeY2, d.leftMB.nzY16+d.upMB[mbx].nzY16, quant.y2, false, whtCoeffBase)
+ d.leftMB.nzY16 = nz
+ d.upMB[mbx].nzY16 = nz
+ d.inverseWHT16()
+ plane = planeY1WithY2
+ }
+
+ var (
+ nzDC, nzAC [4]uint8
+ nzDCMask, nzACMask uint32
+ coeffBase int
+ )
+
+ // Parse the luma coefficients.
+ lnz := unpack[d.leftMB.nzMask&0x0f]
+ unz := unpack[d.upMB[mbx].nzMask&0x0f]
+ for y := 0; y < 4; y++ {
+ nz := lnz[y]
+ for x := 0; x < 4; x++ {
+ nz = d.parseResiduals4(partition, plane, nz+unz[x], quant.y1, d.usePredY16, coeffBase)
+ unz[x] = nz
+ nzAC[x] = nz
+ nzDC[x] = btou(d.coeff[coeffBase] != 0)
+ coeffBase += 16
+ }
+ lnz[y] = nz
+ nzDCMask |= pack(nzDC, y*4)
+ nzACMask |= pack(nzAC, y*4)
+ }
+ lnzMask := pack(lnz, 0)
+ unzMask := pack(unz, 0)
+
+ // Parse the chroma coefficients.
+ lnz = unpack[d.leftMB.nzMask>>4]
+ unz = unpack[d.upMB[mbx].nzMask>>4]
+ for c := 0; c < 4; c += 2 {
+ for y := 0; y < 2; y++ {
+ nz := lnz[y+c]
+ for x := 0; x < 2; x++ {
+ nz = d.parseResiduals4(partition, planeUV, nz+unz[x+c], quant.uv, false, coeffBase)
+ unz[x+c] = nz
+ nzAC[y*2+x] = nz
+ nzDC[y*2+x] = btou(d.coeff[coeffBase] != 0)
+ coeffBase += 16
+ }
+ lnz[y+c] = nz
+ }
+ nzDCMask |= pack(nzDC, 16+c*2)
+ nzACMask |= pack(nzAC, 16+c*2)
+ }
+ lnzMask |= pack(lnz, 4)
+ unzMask |= pack(unz, 4)
+
+ // Save decoder state.
+ d.leftMB.nzMask = uint8(lnzMask)
+ d.upMB[mbx].nzMask = uint8(unzMask)
+ d.nzDCMask = nzDCMask
+ d.nzACMask = nzACMask
+}
+
+// reconstructMacroblock applies the predictor functions and adds the inverse-
+// DCT transformed residuals to recover the YCbCr data.
+func (d *Decoder) reconstructMacroblock(mbx, mby int) {
+ if d.usePredY16 {
+ p := checkTopLeftPred(mbx, mby, d.predY16)
+ predFunc16[p](d, 1, 8)
+ for j := 0; j < 4; j++ {
+ for i := 0; i < 4; i++ {
+ n := 4*j + i
+ y := 4*j + 1
+ x := 4*i + 8
+ mask := uint32(1) << uint(n)
+ if d.nzACMask&mask != 0 {
+ d.inverseDCT4(y, x, 16*n)
+ } else if d.nzDCMask&mask != 0 {
+ d.inverseDCT4DCOnly(y, x, 16*n)
+ }
+ }
+ }
+ } else {
+ for j := 0; j < 4; j++ {
+ for i := 0; i < 4; i++ {
+ n := 4*j + i
+ y := 4*j + 1
+ x := 4*i + 8
+ predFunc4[d.predY4[j][i]](d, y, x)
+ mask := uint32(1) << uint(n)
+ if d.nzACMask&mask != 0 {
+ d.inverseDCT4(y, x, 16*n)
+ } else if d.nzDCMask&mask != 0 {
+ d.inverseDCT4DCOnly(y, x, 16*n)
+ }
+ }
+ }
+ }
+ p := checkTopLeftPred(mbx, mby, d.predC8)
+ predFunc8[p](d, ybrBY, ybrBX)
+ if d.nzACMask&0x0f0000 != 0 {
+ d.inverseDCT8(ybrBY, ybrBX, bCoeffBase)
+ } else if d.nzDCMask&0x0f0000 != 0 {
+ d.inverseDCT8DCOnly(ybrBY, ybrBX, bCoeffBase)
+ }
+ predFunc8[p](d, ybrRY, ybrRX)
+ if d.nzACMask&0xf00000 != 0 {
+ d.inverseDCT8(ybrRY, ybrRX, rCoeffBase)
+ } else if d.nzDCMask&0xf00000 != 0 {
+ d.inverseDCT8DCOnly(ybrRY, ybrRX, rCoeffBase)
+ }
+}
+
+// reconstruct reconstructs one macroblock.
+func (d *Decoder) reconstruct(mbx, mby int) {
+ if d.segmentHeader.updateMap {
+ if !d.fp.readBit(d.segmentHeader.prob[0]) {
+ d.segment = int(d.fp.readUint(d.segmentHeader.prob[1], 1))
+ } else {
+ d.segment = int(d.fp.readUint(d.segmentHeader.prob[2], 1)) + 2
+ }
+ }
+ skip := false
+ if d.useSkipProb {
+ skip = d.fp.readBit(d.skipProb)
+ }
+ // Prepare the workspace.
+ for i := range d.coeff {
+ d.coeff[i] = 0
+ }
+ d.prepareYBR(mbx, mby)
+ // Parse the predictor modes.
+ d.usePredY16 = d.fp.readBit(145)
+ if d.usePredY16 {
+ d.parsePredModeY16(mbx)
+ } else {
+ d.parsePredModeY4(mbx)
+ }
+ d.parsePredModeC8()
+ // Parse the residuals.
+ if !skip {
+ d.parseResiduals(mbx, mby)
+ } else {
+ if d.usePredY16 {
+ d.leftMB.nzY16 = 0
+ d.upMB[mbx].nzY16 = 0
+ }
+ d.leftMB.nzMask = 0
+ d.upMB[mbx].nzMask = 0
+ d.nzDCMask = 0
+ d.nzACMask = 0
+ }
+ // Reconstruct the YCbCr data and copy it to the image.
+ d.reconstructMacroblock(mbx, mby)
+ for i, y := (mby*d.img.YStride+mbx)*16, 0; y < 16; i, y = i+d.img.YStride, y+1 {
+ copy(d.img.Y[i:i+16], d.ybr[ybrYY+y][ybrYX:ybrYX+16])
+ }
+ for i, y := (mby*d.img.CStride+mbx)*8, 0; y < 8; i, y = i+d.img.CStride, y+1 {
+ copy(d.img.Cb[i:i+8], d.ybr[ybrBY+y][ybrBX:ybrBX+8])
+ copy(d.img.Cr[i:i+8], d.ybr[ybrRY+y][ybrRX:ybrRX+8])
+ }
+}
diff --git a/vp8/token.go b/vp8/token.go
new file mode 100644
index 0000000..da99cf0
--- /dev/null
+++ b/vp8/token.go
@@ -0,0 +1,381 @@
+// Copyright 2011 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 vp8
+
+// This file contains token probabilities for decoding DCT/WHT coefficients, as
+// specified in chapter 13.
+
+func (d *Decoder) parseTokenProb() {
+ for i := range d.tokenProb {
+ for j := range d.tokenProb[i] {
+ for k := range d.tokenProb[i][j] {
+ for l := range d.tokenProb[i][j][k] {
+ if d.fp.readBit(tokenProbUpdateProb[i][j][k][l]) {
+ d.tokenProb[i][j][k][l] = uint8(d.fp.readUint(uniformProb, 8))
+ }
+ }
+ }
+ }
+ }
+}
+
+// The plane enumeration is specified in section 13.3.
+const (
+ planeY1WithY2 = iota
+ planeY2
+ planeUV
+ planeY1SansY2
+ nPlane
+)
+
+const (
+ nBand = 8
+ nContext = 3
+ nProb = 11
+)
+
+// Token probability update probabilities are specified in section 13.4.
+var tokenProbUpdateProb = [nPlane][nBand][nContext][nProb]uint8{
+ {
+ {
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {176, 246, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {223, 241, 252, 255, 255, 255, 255, 255, 255, 255, 255},
+ {249, 253, 253, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 244, 252, 255, 255, 255, 255, 255, 255, 255, 255},
+ {234, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 246, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {239, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {254, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 248, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {251, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {251, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {254, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 254, 253, 255, 254, 255, 255, 255, 255, 255, 255},
+ {250, 255, 254, 255, 254, 255, 255, 255, 255, 255, 255},
+ {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ },
+ {
+ {
+ {217, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {225, 252, 241, 253, 255, 255, 254, 255, 255, 255, 255},
+ {234, 250, 241, 250, 253, 255, 253, 254, 255, 255, 255},
+ },
+ {
+ {255, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {223, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {238, 253, 254, 254, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 248, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {249, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 253, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {247, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {252, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 254, 253, 255, 255, 255, 255, 255, 255, 255, 255},
+ {250, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ },
+ {
+ {
+ {186, 251, 250, 255, 255, 255, 255, 255, 255, 255, 255},
+ {234, 251, 244, 254, 255, 255, 255, 255, 255, 255, 255},
+ {251, 251, 243, 253, 254, 255, 254, 255, 255, 255, 255},
+ },
+ {
+ {255, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {236, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {251, 253, 253, 254, 254, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {254, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {254, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ },
+ {
+ {
+ {248, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {250, 254, 252, 254, 255, 255, 255, 255, 255, 255, 255},
+ {248, 254, 249, 253, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 253, 253, 255, 255, 255, 255, 255, 255, 255, 255},
+ {246, 253, 253, 255, 255, 255, 255, 255, 255, 255, 255},
+ {252, 254, 251, 254, 254, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 254, 252, 255, 255, 255, 255, 255, 255, 255, 255},
+ {248, 254, 253, 255, 255, 255, 255, 255, 255, 255, 255},
+ {253, 255, 254, 254, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 251, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {245, 251, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {253, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 251, 253, 255, 255, 255, 255, 255, 255, 255, 255},
+ {252, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 252, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {249, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 255, 253, 255, 255, 255, 255, 255, 255, 255, 255},
+ {250, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ {
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
+ },
+ },
+}
+
+// Default token probabilities are specified in section 13.5.
+var defaultTokenProb = [nPlane][nBand][nContext][nProb]uint8{
+ {
+ {
+ {128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128},
+ {128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128},
+ {128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128},
+ },
+ {
+ {253, 136, 254, 255, 228, 219, 128, 128, 128, 128, 128},
+ {189, 129, 242, 255, 227, 213, 255, 219, 128, 128, 128},
+ {106, 126, 227, 252, 214, 209, 255, 255, 128, 128, 128},
+ },
+ {
+ {1, 98, 248, 255, 236, 226, 255, 255, 128, 128, 128},
+ {181, 133, 238, 254, 221, 234, 255, 154, 128, 128, 128},
+ {78, 134, 202, 247, 198, 180, 255, 219, 128, 128, 128},
+ },
+ {
+ {1, 185, 249, 255, 243, 255, 128, 128, 128, 128, 128},
+ {184, 150, 247, 255, 236, 224, 128, 128, 128, 128, 128},
+ {77, 110, 216, 255, 236, 230, 128, 128, 128, 128, 128},
+ },
+ {
+ {1, 101, 251, 255, 241, 255, 128, 128, 128, 128, 128},
+ {170, 139, 241, 252, 236, 209, 255, 255, 128, 128, 128},
+ {37, 116, 196, 243, 228, 255, 255, 255, 128, 128, 128},
+ },
+ {
+ {1, 204, 254, 255, 245, 255, 128, 128, 128, 128, 128},
+ {207, 160, 250, 255, 238, 128, 128, 128, 128, 128, 128},
+ {102, 103, 231, 255, 211, 171, 128, 128, 128, 128, 128},
+ },
+ {
+ {1, 152, 252, 255, 240, 255, 128, 128, 128, 128, 128},
+ {177, 135, 243, 255, 234, 225, 128, 128, 128, 128, 128},
+ {80, 129, 211, 255, 194, 224, 128, 128, 128, 128, 128},
+ },
+ {
+ {1, 1, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ {246, 1, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ {255, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128},
+ },
+ },
+ {
+ {
+ {198, 35, 237, 223, 193, 187, 162, 160, 145, 155, 62},
+ {131, 45, 198, 221, 172, 176, 220, 157, 252, 221, 1},
+ {68, 47, 146, 208, 149, 167, 221, 162, 255, 223, 128},
+ },
+ {
+ {1, 149, 241, 255, 221, 224, 255, 255, 128, 128, 128},
+ {184, 141, 234, 253, 222, 220, 255, 199, 128, 128, 128},
+ {81, 99, 181, 242, 176, 190, 249, 202, 255, 255, 128},
+ },
+ {
+ {1, 129, 232, 253, 214, 197, 242, 196, 255, 255, 128},
+ {99, 121, 210, 250, 201, 198, 255, 202, 128, 128, 128},
+ {23, 91, 163, 242, 170, 187, 247, 210, 255, 255, 128},
+ },
+ {
+ {1, 200, 246, 255, 234, 255, 128, 128, 128, 128, 128},
+ {109, 178, 241, 255, 231, 245, 255, 255, 128, 128, 128},
+ {44, 130, 201, 253, 205, 192, 255, 255, 128, 128, 128},
+ },
+ {
+ {1, 132, 239, 251, 219, 209, 255, 165, 128, 128, 128},
+ {94, 136, 225, 251, 218, 190, 255, 255, 128, 128, 128},
+ {22, 100, 174, 245, 186, 161, 255, 199, 128, 128, 128},
+ },
+ {
+ {1, 182, 249, 255, 232, 235, 128, 128, 128, 128, 128},
+ {124, 143, 241, 255, 227, 234, 128, 128, 128, 128, 128},
+ {35, 77, 181, 251, 193, 211, 255, 205, 128, 128, 128},
+ },
+ {
+ {1, 157, 247, 255, 236, 231, 255, 255, 128, 128, 128},
+ {121, 141, 235, 255, 225, 227, 255, 255, 128, 128, 128},
+ {45, 99, 188, 251, 195, 217, 255, 224, 128, 128, 128},
+ },
+ {
+ {1, 1, 251, 255, 213, 255, 128, 128, 128, 128, 128},
+ {203, 1, 248, 255, 255, 128, 128, 128, 128, 128, 128},
+ {137, 1, 177, 255, 224, 255, 128, 128, 128, 128, 128},
+ },
+ },
+ {
+ {
+ {253, 9, 248, 251, 207, 208, 255, 192, 128, 128, 128},
+ {175, 13, 224, 243, 193, 185, 249, 198, 255, 255, 128},
+ {73, 17, 171, 221, 161, 179, 236, 167, 255, 234, 128},
+ },
+ {
+ {1, 95, 247, 253, 212, 183, 255, 255, 128, 128, 128},
+ {239, 90, 244, 250, 211, 209, 255, 255, 128, 128, 128},
+ {155, 77, 195, 248, 188, 195, 255, 255, 128, 128, 128},
+ },
+ {
+ {1, 24, 239, 251, 218, 219, 255, 205, 128, 128, 128},
+ {201, 51, 219, 255, 196, 186, 128, 128, 128, 128, 128},
+ {69, 46, 190, 239, 201, 218, 255, 228, 128, 128, 128},
+ },
+ {
+ {1, 191, 251, 255, 255, 128, 128, 128, 128, 128, 128},
+ {223, 165, 249, 255, 213, 255, 128, 128, 128, 128, 128},
+ {141, 124, 248, 255, 255, 128, 128, 128, 128, 128, 128},
+ },
+ {
+ {1, 16, 248, 255, 255, 128, 128, 128, 128, 128, 128},
+ {190, 36, 230, 255, 236, 255, 128, 128, 128, 128, 128},
+ {149, 1, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ },
+ {
+ {1, 226, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ {247, 192, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ {240, 128, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ },
+ {
+ {1, 134, 252, 255, 255, 128, 128, 128, 128, 128, 128},
+ {213, 62, 250, 255, 255, 128, 128, 128, 128, 128, 128},
+ {55, 93, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ },
+ {
+ {128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128},
+ {128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128},
+ {128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128},
+ },
+ },
+ {
+ {
+ {202, 24, 213, 235, 186, 191, 220, 160, 240, 175, 255},
+ {126, 38, 182, 232, 169, 184, 228, 174, 255, 187, 128},
+ {61, 46, 138, 219, 151, 178, 240, 170, 255, 216, 128},
+ },
+ {
+ {1, 112, 230, 250, 199, 191, 247, 159, 255, 255, 128},
+ {166, 109, 228, 252, 211, 215, 255, 174, 128, 128, 128},
+ {39, 77, 162, 232, 172, 180, 245, 178, 255, 255, 128},
+ },
+ {
+ {1, 52, 220, 246, 198, 199, 249, 220, 255, 255, 128},
+ {124, 74, 191, 243, 183, 193, 250, 221, 255, 255, 128},
+ {24, 71, 130, 219, 154, 170, 243, 182, 255, 255, 128},
+ },
+ {
+ {1, 182, 225, 249, 219, 240, 255, 224, 128, 128, 128},
+ {149, 150, 226, 252, 216, 205, 255, 171, 128, 128, 128},
+ {28, 108, 170, 242, 183, 194, 254, 223, 255, 255, 128},
+ },
+ {
+ {1, 81, 230, 252, 204, 203, 255, 192, 128, 128, 128},
+ {123, 102, 209, 247, 188, 196, 255, 233, 128, 128, 128},
+ {20, 95, 153, 243, 164, 173, 255, 203, 128, 128, 128},
+ },
+ {
+ {1, 222, 248, 255, 216, 213, 128, 128, 128, 128, 128},
+ {168, 175, 246, 252, 235, 205, 255, 255, 128, 128, 128},
+ {47, 116, 215, 255, 211, 212, 255, 255, 128, 128, 128},
+ },
+ {
+ {1, 121, 236, 253, 212, 214, 255, 255, 128, 128, 128},
+ {141, 84, 213, 252, 201, 202, 255, 219, 128, 128, 128},
+ {42, 80, 160, 240, 162, 185, 255, 205, 128, 128, 128},
+ },
+ {
+ {1, 1, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ {244, 1, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ {238, 1, 255, 128, 128, 128, 128, 128, 128, 128, 128},
+ },
+ },
+}
diff --git a/webp/decode.go b/webp/decode.go
new file mode 100644
index 0000000..e58cb53
--- /dev/null
+++ b/webp/decode.go
@@ -0,0 +1,75 @@
+// Copyright 2011 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 webp implements a decoder for WEBP images.
+//
+// WEBP is defined in the VP8 specification at:
+// http://datatracker.ietf.org/doc/rfc6386/
+package webp
+
+import (
+ "errors"
+ "image"
+ "image/color"
+ "io"
+
+ "code.google.com/p/go.image/vp8"
+)
+
+func decode(r io.Reader) (d *vp8.Decoder, fh vp8.FrameHeader, err error) {
+ var b [20]byte
+ if _, err = io.ReadFull(r, b[:]); err != nil {
+ return
+ }
+ if string(b[0:4]) != "RIFF" || string(b[8:16]) != "WEBPVP8 " {
+ err = errors.New("webp: invalid format")
+ return
+ }
+ riffLen := uint32(b[4]) | uint32(b[5])<<8 | uint32(b[6])<<16 | uint32(b[7])<<24
+ dataLen := uint32(b[16]) | uint32(b[17])<<8 | uint32(b[18])<<16 | uint32(b[19])<<24
+ if riffLen < dataLen+12 {
+ err = errors.New("webp: invalid format")
+ return
+ }
+ if dataLen >= 1<<31 {
+ err = errors.New("webp: invalid format")
+ return
+ }
+ d = vp8.NewDecoder()
+ d.Init(r, int(dataLen))
+ fh, err = d.DecodeFrameHeader()
+ if err != nil {
+ d, fh = nil, vp8.FrameHeader{}
+ return
+ }
+ return
+}
+
+// Decode reads a WEBP image from r and returns it as an image.Image.
+func Decode(r io.Reader) (image.Image, error) {
+ d, _, err := decode(r)
+ if err != nil {
+ return nil, err
+ }
+ return d.DecodeFrame()
+}
+
+// DecodeConfig returns the color model and dimensions of a WEBP image without
+// decoding the entire image.
+func DecodeConfig(r io.Reader) (image.Config, error) {
+ _, fh, err := decode(r)
+ if err != nil {
+ return image.Config{}, err
+ }
+ c := image.Config{
+ ColorModel: color.YCbCrModel,
+ Width: fh.Width,
+ Height: fh.Height,
+ }
+ return c, nil
+}
+
+func init() {
+ image.RegisterFormat("webp", "RIFF????WEBPVP8 ", Decode, DecodeConfig)
+}
