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diff --git a/vendor/golang.org/x/image/vp8l/decode.go b/vendor/golang.org/x/image/vp8l/decode.go
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+// 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 - 1)
+ d.bits >>= 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<<ccBits)
+ }
+
+ // Decode the Huffman groups.
+ hGroups, hPix, hBits, err := d.decodeHuffmanGroups(w, h, topLevel, ccBits)
+ if err != nil {
+ return nil, err
+ }
+ hMask, tilesPerRow := int32(0), int32(0)
+ if hBits != 0 {
+ hMask, tilesPerRow = 1<<hBits-1, nTiles(w, hBits)
+ }
+
+ // Decode the pixels.
+ if minCap < 4*w*h {
+ minCap = 4 * w * h
+ }
+ pix := make([]byte, 4*w*h, minCap)
+ p, cachedP := 0, 0
+ x, y := int32(0), int32(0)
+ hg, lookupHG := &hGroups[0], hMask != 0
+ for p < len(pix) {
+ if lookupHG {
+ i := 4 * (tilesPerRow*(y>>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
+}