From e1e8d058a33f7566f9c565d04b0d8b56f9645c35 Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Wed, 25 Apr 2018 09:28:54 +0200 Subject: add vendor --- vendor/golang.org/x/image/vp8/decode.go | 403 ++++++++++++++++++++++++++++++++ 1 file changed, 403 insertions(+) create mode 100644 vendor/golang.org/x/image/vp8/decode.go (limited to 'vendor/golang.org/x/image/vp8/decode.go') diff --git a/vendor/golang.org/x/image/vp8/decode.go b/vendor/golang.org/x/image/vp8/decode.go new file mode 100644 index 0000000..1bb5028 --- /dev/null +++ b/vendor/golang.org/x/image/vp8/decode.go @@ -0,0 +1,403 @@ +// 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 decoder for the VP8 lossy image format. +// +// The VP8 specification is RFC 6386. +package vp8 // import "golang.org/x/image/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 + // Loop filter parameters. + filterParams [nSegment][2]filterParam + perMBFilterParams []filterParam + + // 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 // The libwebp C code calls this !is_i4x4_. + 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.perMBFilterParams = make([]filterParam, d.mbw*d.mbh) + 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 + } + d.computeFilterParams() +} + +// parseOtherPartitions parses the other partitions, as specified in section 9.5. +func (d *Decoder) parseOtherPartitions() error { + const maxNOP = 1 << 3 + var partLens [maxNOP]int + d.nOP = 1 << d.fp.readUint(uniformProb, 2) + + // The final partition length is implied by the the remaining chunk data + // (d.r.n) and the other d.nOP-1 partition lengths. Those d.nOP-1 partition + // lengths are stored as 24-bit uints, i.e. up to 16 MiB per partition. + n := 3 * (d.nOP - 1) + partLens[d.nOP-1] = d.r.n - n + if partLens[d.nOP-1] < 0 { + return io.ErrUnexpectedEOF + } + if n > 0 { + buf := make([]byte, n) + if err := d.r.ReadFull(buf); err != nil { + return err + } + for i := 0; i < d.nOP-1; i++ { + pl := int(buf[3*i+0]) | int(buf[3*i+1])<<8 | int(buf[3*i+2])<<16 + if pl > partLens[d.nOP-1] { + return io.ErrUnexpectedEOF + } + partLens[i] = pl + partLens[d.nOP-1] -= pl + } + } + + // We check if the final partition length can also fit into a 24-bit uint. + // Strictly speaking, this isn't part of the spec, but it guards against a + // malicious WEBP image that is too large to ReadFull the encoded DCT + // coefficients into memory, whether that's because the actual WEBP file is + // too large, or whether its RIFF metadata lists too large a chunk. + if 1<<24 <= partLens[d.nOP-1] { + return errors.New("vp8: too much data to decode") + } + + buf := make([]byte, d.r.n) + if err := d.r.ReadFull(buf); err != nil { + return err + } + for i, pl := range partLens { + if i == d.nOP { + break + } + d.op[i].init(buf[:pl]) + buf = buf[pl:] + } + 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 + } + // Reconstruct the rows. + 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++ { + skip := d.reconstruct(mbx, mby) + fs := d.filterParams[d.segment][btou(!d.usePredY16)] + fs.inner = fs.inner || !skip + d.perMBFilterParams[d.mbw*mby+mbx] = fs + } + } + if d.fp.unexpectedEOF { + return nil, io.ErrUnexpectedEOF + } + for i := 0; i < d.nOP; i++ { + if d.op[i].unexpectedEOF { + return nil, io.ErrUnexpectedEOF + } + } + // Apply the loop filter. + // + // Even if we are using per-segment levels, section 15 says that "loop + // filtering must be skipped entirely if loop_filter_level at either the + // frame header level or macroblock override level is 0". + if d.filterHeader.level != 0 { + if d.filterHeader.simple { + d.simpleFilter() + } else { + d.normalFilter() + } + } + return d.img, nil +} -- cgit v1.2.3