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/vp8l/decode.go | 603 +++++++++++++++++++++++++++++++ 1 file changed, 603 insertions(+) create mode 100644 vendor/golang.org/x/image/vp8l/decode.go (limited to 'vendor/golang.org/x/image/vp8l/decode.go') diff --git a/vendor/golang.org/x/image/vp8l/decode.go b/vendor/golang.org/x/image/vp8l/decode.go new file mode 100644 index 0000000..4319487 --- /dev/null +++ b/vendor/golang.org/x/image/vp8l/decode.go @@ -0,0 +1,603 @@ +// Copyright 2014 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 vp8l implements a decoder for the VP8L lossless image format. +// +// The VP8L specification is at: +// https://developers.google.com/speed/webp/docs/riff_container +package vp8l // import "golang.org/x/image/vp8l" + +import ( + "bufio" + "errors" + "image" + "image/color" + "io" +) + +var ( + errInvalidCodeLengths = errors.New("vp8l: invalid code lengths") + errInvalidHuffmanTree = errors.New("vp8l: invalid Huffman tree") +) + +// colorCacheMultiplier is the multiplier used for the color cache hash +// function, specified in section 4.2.3. +const colorCacheMultiplier = 0x1e35a7bd + +// distanceMapTable is the look-up table for distanceMap. +var distanceMapTable = [120]uint8{ + 0x18, 0x07, 0x17, 0x19, 0x28, 0x06, 0x27, 0x29, 0x16, 0x1a, + 0x26, 0x2a, 0x38, 0x05, 0x37, 0x39, 0x15, 0x1b, 0x36, 0x3a, + 0x25, 0x2b, 0x48, 0x04, 0x47, 0x49, 0x14, 0x1c, 0x35, 0x3b, + 0x46, 0x4a, 0x24, 0x2c, 0x58, 0x45, 0x4b, 0x34, 0x3c, 0x03, + 0x57, 0x59, 0x13, 0x1d, 0x56, 0x5a, 0x23, 0x2d, 0x44, 0x4c, + 0x55, 0x5b, 0x33, 0x3d, 0x68, 0x02, 0x67, 0x69, 0x12, 0x1e, + 0x66, 0x6a, 0x22, 0x2e, 0x54, 0x5c, 0x43, 0x4d, 0x65, 0x6b, + 0x32, 0x3e, 0x78, 0x01, 0x77, 0x79, 0x53, 0x5d, 0x11, 0x1f, + 0x64, 0x6c, 0x42, 0x4e, 0x76, 0x7a, 0x21, 0x2f, 0x75, 0x7b, + 0x31, 0x3f, 0x63, 0x6d, 0x52, 0x5e, 0x00, 0x74, 0x7c, 0x41, + 0x4f, 0x10, 0x20, 0x62, 0x6e, 0x30, 0x73, 0x7d, 0x51, 0x5f, + 0x40, 0x72, 0x7e, 0x61, 0x6f, 0x50, 0x71, 0x7f, 0x60, 0x70, +} + +// distanceMap maps a LZ77 backwards reference distance to a two-dimensional +// pixel offset, specified in section 4.2.2. +func distanceMap(w int32, code uint32) int32 { + if int32(code) > int32(len(distanceMapTable)) { + return int32(code) - int32(len(distanceMapTable)) + } + distCode := int32(distanceMapTable[code-1]) + yOffset := distCode >> 4 + xOffset := 8 - distCode&0xf + if d := yOffset*w + xOffset; d >= 1 { + return d + } + return 1 +} + +// decoder holds the bit-stream for a VP8L image. +type decoder struct { + r io.ByteReader + bits uint32 + nBits uint32 +} + +// read reads the next n bits from the decoder's bit-stream. +func (d *decoder) read(n uint32) (uint32, error) { + for d.nBits < n { + c, err := d.r.ReadByte() + if err != nil { + if err == io.EOF { + err = io.ErrUnexpectedEOF + } + return 0, err + } + d.bits |= uint32(c) << d.nBits + d.nBits += 8 + } + u := d.bits & (1<>= n + d.nBits -= n + return u, nil +} + +// decodeTransform decodes the next transform and the width of the image after +// transformation (or equivalently, before inverse transformation), specified +// in section 3. +func (d *decoder) decodeTransform(w int32, h int32) (t transform, newWidth int32, err error) { + t.oldWidth = w + t.transformType, err = d.read(2) + if err != nil { + return transform{}, 0, err + } + switch t.transformType { + case transformTypePredictor, transformTypeCrossColor: + t.bits, err = d.read(3) + if err != nil { + return transform{}, 0, err + } + t.bits += 2 + t.pix, err = d.decodePix(nTiles(w, t.bits), nTiles(h, t.bits), 0, false) + if err != nil { + return transform{}, 0, err + } + case transformTypeSubtractGreen: + // No-op. + case transformTypeColorIndexing: + nColors, err := d.read(8) + if err != nil { + return transform{}, 0, err + } + nColors++ + t.bits = 0 + switch { + case nColors <= 2: + t.bits = 3 + case nColors <= 4: + t.bits = 2 + case nColors <= 16: + t.bits = 1 + } + w = nTiles(w, t.bits) + pix, err := d.decodePix(int32(nColors), 1, 4*256, false) + if err != nil { + return transform{}, 0, err + } + for p := 4; p < len(pix); p += 4 { + pix[p+0] += pix[p-4] + pix[p+1] += pix[p-3] + pix[p+2] += pix[p-2] + pix[p+3] += pix[p-1] + } + // The spec says that "if the index is equal or larger than color_table_size, + // the argb color value should be set to 0x00000000 (transparent black)." + // We re-slice up to 256 4-byte pixels. + t.pix = pix[:4*256] + } + return t, w, nil +} + +// repeatsCodeLength is the minimum code length for repeated codes. +const repeatsCodeLength = 16 + +// These magic numbers are specified at the end of section 5.2.2. +// The 3-length arrays apply to code lengths >= repeatsCodeLength. +var ( + codeLengthCodeOrder = [19]uint8{ + 17, 18, 0, 1, 2, 3, 4, 5, 16, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, + } + repeatBits = [3]uint8{2, 3, 7} + repeatOffsets = [3]uint8{3, 3, 11} +) + +// decodeCodeLengths decodes a Huffman tree's code lengths which are themselves +// encoded via a Huffman tree, specified in section 5.2.2. +func (d *decoder) decodeCodeLengths(dst []uint32, codeLengthCodeLengths []uint32) error { + h := hTree{} + if err := h.build(codeLengthCodeLengths); err != nil { + return err + } + + maxSymbol := len(dst) + useLength, err := d.read(1) + if err != nil { + return err + } + if useLength != 0 { + n, err := d.read(3) + if err != nil { + return err + } + n = 2 + 2*n + ms, err := d.read(n) + if err != nil { + return err + } + maxSymbol = int(ms) + 2 + if maxSymbol > len(dst) { + return errInvalidCodeLengths + } + } + + // The spec says that "if code 16 [meaning repeat] is used before + // a non-zero value has been emitted, a value of 8 is repeated." + prevCodeLength := uint32(8) + + for symbol := 0; symbol < len(dst); { + if maxSymbol == 0 { + break + } + maxSymbol-- + codeLength, err := h.next(d) + if err != nil { + return err + } + if codeLength < repeatsCodeLength { + dst[symbol] = codeLength + symbol++ + if codeLength != 0 { + prevCodeLength = codeLength + } + continue + } + + repeat, err := d.read(uint32(repeatBits[codeLength-repeatsCodeLength])) + if err != nil { + return err + } + repeat += uint32(repeatOffsets[codeLength-repeatsCodeLength]) + if symbol+int(repeat) > len(dst) { + return errInvalidCodeLengths + } + // A code length of 16 repeats the previous non-zero code. + // A code length of 17 or 18 repeats zeroes. + cl := uint32(0) + if codeLength == 16 { + cl = prevCodeLength + } + for ; repeat > 0; repeat-- { + dst[symbol] = cl + symbol++ + } + } + return nil +} + +// decodeHuffmanTree decodes a Huffman tree into h. +func (d *decoder) decodeHuffmanTree(h *hTree, alphabetSize uint32) error { + useSimple, err := d.read(1) + if err != nil { + return err + } + if useSimple != 0 { + nSymbols, err := d.read(1) + if err != nil { + return err + } + nSymbols++ + firstSymbolLengthCode, err := d.read(1) + if err != nil { + return err + } + firstSymbolLengthCode = 7*firstSymbolLengthCode + 1 + var symbols [2]uint32 + symbols[0], err = d.read(firstSymbolLengthCode) + if err != nil { + return err + } + if nSymbols == 2 { + symbols[1], err = d.read(8) + if err != nil { + return err + } + } + return h.buildSimple(nSymbols, symbols, alphabetSize) + } + + nCodes, err := d.read(4) + if err != nil { + return err + } + nCodes += 4 + if int(nCodes) > len(codeLengthCodeOrder) { + return errInvalidHuffmanTree + } + codeLengthCodeLengths := [len(codeLengthCodeOrder)]uint32{} + for i := uint32(0); i < nCodes; i++ { + codeLengthCodeLengths[codeLengthCodeOrder[i]], err = d.read(3) + if err != nil { + return err + } + } + codeLengths := make([]uint32, alphabetSize) + if err = d.decodeCodeLengths(codeLengths, codeLengthCodeLengths[:]); err != nil { + return err + } + return h.build(codeLengths) +} + +const ( + huffGreen = 0 + huffRed = 1 + huffBlue = 2 + huffAlpha = 3 + huffDistance = 4 + nHuff = 5 +) + +// hGroup is an array of 5 Huffman trees. +type hGroup [nHuff]hTree + +// decodeHuffmanGroups decodes the one or more hGroups used to decode the pixel +// data. If one hGroup is used for the entire image, then hPix and hBits will +// be zero. If more than one hGroup is used, then hPix contains the meta-image +// that maps tiles to hGroup index, and hBits contains the log-2 tile size. +func (d *decoder) decodeHuffmanGroups(w int32, h int32, topLevel bool, ccBits uint32) ( + hGroups []hGroup, hPix []byte, hBits uint32, err error) { + + maxHGroupIndex := 0 + if topLevel { + useMeta, err := d.read(1) + if err != nil { + return nil, nil, 0, err + } + if useMeta != 0 { + hBits, err = d.read(3) + if err != nil { + return nil, nil, 0, err + } + hBits += 2 + hPix, err = d.decodePix(nTiles(w, hBits), nTiles(h, hBits), 0, false) + if err != nil { + return nil, nil, 0, err + } + for p := 0; p < len(hPix); p += 4 { + i := int(hPix[p])<<8 | int(hPix[p+1]) + if maxHGroupIndex < i { + maxHGroupIndex = i + } + } + } + } + hGroups = make([]hGroup, maxHGroupIndex+1) + for i := range hGroups { + for j, alphabetSize := range alphabetSizes { + if j == 0 && ccBits > 0 { + alphabetSize += 1 << ccBits + } + if err := d.decodeHuffmanTree(&hGroups[i][j], alphabetSize); err != nil { + return nil, nil, 0, err + } + } + } + return hGroups, hPix, hBits, nil +} + +const ( + nLiteralCodes = 256 + nLengthCodes = 24 + nDistanceCodes = 40 +) + +var alphabetSizes = [nHuff]uint32{ + nLiteralCodes + nLengthCodes, + nLiteralCodes, + nLiteralCodes, + nLiteralCodes, + nDistanceCodes, +} + +// decodePix decodes pixel data, specified in section 5.2.2. +func (d *decoder) decodePix(w int32, h int32, minCap int32, topLevel bool) ([]byte, error) { + // Decode the color cache parameters. + ccBits, ccShift, ccEntries := uint32(0), uint32(0), ([]uint32)(nil) + useColorCache, err := d.read(1) + if err != nil { + return nil, err + } + if useColorCache != 0 { + ccBits, err = d.read(4) + if err != nil { + return nil, err + } + if ccBits < 1 || 11 < ccBits { + return nil, errors.New("vp8l: invalid color cache parameters") + } + ccShift = 32 - ccBits + ccEntries = make([]uint32, 1<>hBits) + (x >> hBits)) + hg = &hGroups[uint32(hPix[i])<<8|uint32(hPix[i+1])] + } + + green, err := hg[huffGreen].next(d) + if err != nil { + return nil, err + } + switch { + case green < nLiteralCodes: + // We have a literal pixel. + red, err := hg[huffRed].next(d) + if err != nil { + return nil, err + } + blue, err := hg[huffBlue].next(d) + if err != nil { + return nil, err + } + alpha, err := hg[huffAlpha].next(d) + if err != nil { + return nil, err + } + pix[p+0] = uint8(red) + pix[p+1] = uint8(green) + pix[p+2] = uint8(blue) + pix[p+3] = uint8(alpha) + p += 4 + + x++ + if x == w { + x, y = 0, y+1 + } + lookupHG = hMask != 0 && x&hMask == 0 + + case green < nLiteralCodes+nLengthCodes: + // We have a LZ77 backwards reference. + length, err := d.lz77Param(green - nLiteralCodes) + if err != nil { + return nil, err + } + distSym, err := hg[huffDistance].next(d) + if err != nil { + return nil, err + } + distCode, err := d.lz77Param(distSym) + if err != nil { + return nil, err + } + dist := distanceMap(w, distCode) + pEnd := p + 4*int(length) + q := p - 4*int(dist) + qEnd := pEnd - 4*int(dist) + if p < 0 || len(pix) < pEnd || q < 0 || len(pix) < qEnd { + return nil, errors.New("vp8l: invalid LZ77 parameters") + } + for ; p < pEnd; p, q = p+1, q+1 { + pix[p] = pix[q] + } + + x += int32(length) + for x >= w { + x, y = x-w, y+1 + } + lookupHG = hMask != 0 + + default: + // We have a color cache lookup. First, insert previous pixels + // into the cache. Note that VP8L assumes ARGB order, but the + // Go image.RGBA type is in RGBA order. + for ; cachedP < p; cachedP += 4 { + argb := uint32(pix[cachedP+0])<<16 | + uint32(pix[cachedP+1])<<8 | + uint32(pix[cachedP+2])<<0 | + uint32(pix[cachedP+3])<<24 + ccEntries[(argb*colorCacheMultiplier)>>ccShift] = argb + } + green -= nLiteralCodes + nLengthCodes + if int(green) >= len(ccEntries) { + return nil, errors.New("vp8l: invalid color cache index") + } + argb := ccEntries[green] + pix[p+0] = uint8(argb >> 16) + pix[p+1] = uint8(argb >> 8) + pix[p+2] = uint8(argb >> 0) + pix[p+3] = uint8(argb >> 24) + p += 4 + + x++ + if x == w { + x, y = 0, y+1 + } + lookupHG = hMask != 0 && x&hMask == 0 + } + } + return pix, nil +} + +// lz77Param returns the next LZ77 parameter: a length or a distance, specified +// in section 4.2.2. +func (d *decoder) lz77Param(symbol uint32) (uint32, error) { + if symbol < 4 { + return symbol + 1, nil + } + extraBits := (symbol - 2) >> 1 + offset := (2 + symbol&1) << extraBits + n, err := d.read(extraBits) + if err != nil { + return 0, err + } + return offset + n + 1, nil +} + +// decodeHeader decodes the VP8L header from r. +func decodeHeader(r io.Reader) (d *decoder, w int32, h int32, err error) { + rr, ok := r.(io.ByteReader) + if !ok { + rr = bufio.NewReader(r) + } + d = &decoder{r: rr} + magic, err := d.read(8) + if err != nil { + return nil, 0, 0, err + } + if magic != 0x2f { + return nil, 0, 0, errors.New("vp8l: invalid header") + } + width, err := d.read(14) + if err != nil { + return nil, 0, 0, err + } + width++ + height, err := d.read(14) + if err != nil { + return nil, 0, 0, err + } + height++ + _, err = d.read(1) // Read and ignore the hasAlpha hint. + if err != nil { + return nil, 0, 0, err + } + version, err := d.read(3) + if err != nil { + return nil, 0, 0, err + } + if version != 0 { + return nil, 0, 0, errors.New("vp8l: invalid version") + } + return d, int32(width), int32(height), nil +} + +// DecodeConfig decodes the color model and dimensions of a VP8L image from r. +func DecodeConfig(r io.Reader) (image.Config, error) { + _, w, h, err := decodeHeader(r) + if err != nil { + return image.Config{}, err + } + return image.Config{ + ColorModel: color.NRGBAModel, + Width: int(w), + Height: int(h), + }, nil +} + +// Decode decodes a VP8L image from r. +func Decode(r io.Reader) (image.Image, error) { + d, w, h, err := decodeHeader(r) + if err != nil { + return nil, err + } + // Decode the transforms. + var ( + nTransforms int + transforms [nTransformTypes]transform + transformsSeen [nTransformTypes]bool + originalW = w + ) + for { + more, err := d.read(1) + if err != nil { + return nil, err + } + if more == 0 { + break + } + var t transform + t, w, err = d.decodeTransform(w, h) + if err != nil { + return nil, err + } + if transformsSeen[t.transformType] { + return nil, errors.New("vp8l: repeated transform") + } + transformsSeen[t.transformType] = true + transforms[nTransforms] = t + nTransforms++ + } + // Decode the transformed pixels. + pix, err := d.decodePix(w, h, 0, true) + if err != nil { + return nil, err + } + // Apply the inverse transformations. + for i := nTransforms - 1; i >= 0; i-- { + t := &transforms[i] + pix = inverseTransforms[t.transformType](t, pix, h) + } + return &image.NRGBA{ + Pix: pix, + Stride: 4 * int(originalW), + Rect: image.Rect(0, 0, int(originalW), int(h)), + }, nil +} -- cgit v1.2.3