From 64fa922ec013079f8f0c90fc9e93c56db3611d30 Mon Sep 17 00:00:00 2001 From: Tulir Asokan Date: Sun, 22 Apr 2018 21:25:06 +0300 Subject: Switch to dep --- vendor/golang.org/x/image/webp/decode.go | 272 +++++++++++++++++++++++++++++++ 1 file changed, 272 insertions(+) create mode 100644 vendor/golang.org/x/image/webp/decode.go (limited to 'vendor/golang.org/x/image/webp/decode.go') diff --git a/vendor/golang.org/x/image/webp/decode.go b/vendor/golang.org/x/image/webp/decode.go new file mode 100644 index 0000000..111f358 --- /dev/null +++ b/vendor/golang.org/x/image/webp/decode.go @@ -0,0 +1,272 @@ +// 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. + +// +build go1.6 + +package webp + +import ( + "bytes" + "errors" + "image" + "image/color" + "io" + + "golang.org/x/image/riff" + "golang.org/x/image/vp8" + "golang.org/x/image/vp8l" +) + +var errInvalidFormat = errors.New("webp: invalid format") + +var ( + fccALPH = riff.FourCC{'A', 'L', 'P', 'H'} + fccVP8 = riff.FourCC{'V', 'P', '8', ' '} + fccVP8L = riff.FourCC{'V', 'P', '8', 'L'} + fccVP8X = riff.FourCC{'V', 'P', '8', 'X'} + fccWEBP = riff.FourCC{'W', 'E', 'B', 'P'} +) + +func decode(r io.Reader, configOnly bool) (image.Image, image.Config, error) { + formType, riffReader, err := riff.NewReader(r) + if err != nil { + return nil, image.Config{}, err + } + if formType != fccWEBP { + return nil, image.Config{}, errInvalidFormat + } + + var ( + alpha []byte + alphaStride int + wantAlpha bool + widthMinusOne uint32 + heightMinusOne uint32 + buf [10]byte + ) + for { + chunkID, chunkLen, chunkData, err := riffReader.Next() + if err == io.EOF { + err = errInvalidFormat + } + if err != nil { + return nil, image.Config{}, err + } + + switch chunkID { + case fccALPH: + if !wantAlpha { + return nil, image.Config{}, errInvalidFormat + } + wantAlpha = false + // Read the Pre-processing | Filter | Compression byte. + if _, err := io.ReadFull(chunkData, buf[:1]); err != nil { + if err == io.EOF { + err = errInvalidFormat + } + return nil, image.Config{}, err + } + alpha, alphaStride, err = readAlpha(chunkData, widthMinusOne, heightMinusOne, buf[0]&0x03) + if err != nil { + return nil, image.Config{}, err + } + unfilterAlpha(alpha, alphaStride, (buf[0]>>2)&0x03) + + case fccVP8: + if wantAlpha || int32(chunkLen) < 0 { + return nil, image.Config{}, errInvalidFormat + } + d := vp8.NewDecoder() + d.Init(chunkData, int(chunkLen)) + fh, err := d.DecodeFrameHeader() + if err != nil { + return nil, image.Config{}, err + } + if configOnly { + return nil, image.Config{ + ColorModel: color.YCbCrModel, + Width: fh.Width, + Height: fh.Height, + }, nil + } + m, err := d.DecodeFrame() + if err != nil { + return nil, image.Config{}, err + } + if alpha != nil { + return &image.NYCbCrA{ + YCbCr: *m, + A: alpha, + AStride: alphaStride, + }, image.Config{}, nil + } + return m, image.Config{}, nil + + case fccVP8L: + if wantAlpha || alpha != nil { + return nil, image.Config{}, errInvalidFormat + } + if configOnly { + c, err := vp8l.DecodeConfig(chunkData) + return nil, c, err + } + m, err := vp8l.Decode(chunkData) + return m, image.Config{}, err + + case fccVP8X: + if chunkLen != 10 { + return nil, image.Config{}, errInvalidFormat + } + if _, err := io.ReadFull(chunkData, buf[:10]); err != nil { + return nil, image.Config{}, err + } + const ( + animationBit = 1 << 1 + xmpMetadataBit = 1 << 2 + exifMetadataBit = 1 << 3 + alphaBit = 1 << 4 + iccProfileBit = 1 << 5 + ) + if buf[0] != alphaBit { + return nil, image.Config{}, errors.New("webp: non-Alpha VP8X is not implemented") + } + widthMinusOne = uint32(buf[4]) | uint32(buf[5])<<8 | uint32(buf[6])<<16 + heightMinusOne = uint32(buf[7]) | uint32(buf[8])<<8 | uint32(buf[9])<<16 + if configOnly { + return nil, image.Config{ + ColorModel: color.NYCbCrAModel, + Width: int(widthMinusOne) + 1, + Height: int(heightMinusOne) + 1, + }, nil + } + wantAlpha = true + + default: + return nil, image.Config{}, errInvalidFormat + } + } +} + +func readAlpha(chunkData io.Reader, widthMinusOne, heightMinusOne uint32, compression byte) ( + alpha []byte, alphaStride int, err error) { + + switch compression { + case 0: + w := int(widthMinusOne) + 1 + h := int(heightMinusOne) + 1 + alpha = make([]byte, w*h) + if _, err := io.ReadFull(chunkData, alpha); err != nil { + return nil, 0, err + } + return alpha, w, nil + + case 1: + // Read the VP8L-compressed alpha values. First, synthesize a 5-byte VP8L header: + // a 1-byte magic number, a 14-bit widthMinusOne, a 14-bit heightMinusOne, + // a 1-bit (ignored, zero) alphaIsUsed and a 3-bit (zero) version. + // TODO(nigeltao): be more efficient than decoding an *image.NRGBA just to + // extract the green values to a separately allocated []byte. Fixing this + // will require changes to the vp8l package's API. + if widthMinusOne > 0x3fff || heightMinusOne > 0x3fff { + return nil, 0, errors.New("webp: invalid format") + } + alphaImage, err := vp8l.Decode(io.MultiReader( + bytes.NewReader([]byte{ + 0x2f, // VP8L magic number. + uint8(widthMinusOne), + uint8(widthMinusOne>>8) | uint8(heightMinusOne<<6), + uint8(heightMinusOne >> 2), + uint8(heightMinusOne >> 10), + }), + chunkData, + )) + if err != nil { + return nil, 0, err + } + // The green values of the inner NRGBA image are the alpha values of the + // outer NYCbCrA image. + pix := alphaImage.(*image.NRGBA).Pix + alpha = make([]byte, len(pix)/4) + for i := range alpha { + alpha[i] = pix[4*i+1] + } + return alpha, int(widthMinusOne) + 1, nil + } + return nil, 0, errInvalidFormat +} + +func unfilterAlpha(alpha []byte, alphaStride int, filter byte) { + if len(alpha) == 0 || alphaStride == 0 { + return + } + switch filter { + case 1: // Horizontal filter. + for i := 1; i < alphaStride; i++ { + alpha[i] += alpha[i-1] + } + for i := alphaStride; i < len(alpha); i += alphaStride { + // The first column is equivalent to the vertical filter. + alpha[i] += alpha[i-alphaStride] + + for j := 1; j < alphaStride; j++ { + alpha[i+j] += alpha[i+j-1] + } + } + + case 2: // Vertical filter. + // The first row is equivalent to the horizontal filter. + for i := 1; i < alphaStride; i++ { + alpha[i] += alpha[i-1] + } + + for i := alphaStride; i < len(alpha); i++ { + alpha[i] += alpha[i-alphaStride] + } + + case 3: // Gradient filter. + // The first row is equivalent to the horizontal filter. + for i := 1; i < alphaStride; i++ { + alpha[i] += alpha[i-1] + } + + for i := alphaStride; i < len(alpha); i += alphaStride { + // The first column is equivalent to the vertical filter. + alpha[i] += alpha[i-alphaStride] + + // The interior is predicted on the three top/left pixels. + for j := 1; j < alphaStride; j++ { + c := int(alpha[i+j-alphaStride-1]) + b := int(alpha[i+j-alphaStride]) + a := int(alpha[i+j-1]) + x := a + b - c + if x < 0 { + x = 0 + } else if x > 255 { + x = 255 + } + alpha[i+j] += uint8(x) + } + } + } +} + +// Decode reads a WEBP image from r and returns it as an image.Image. +func Decode(r io.Reader) (image.Image, error) { + m, _, err := decode(r, false) + if err != nil { + return nil, err + } + return m, err +} + +// DecodeConfig returns the color model and dimensions of a WEBP image without +// decoding the entire image. +func DecodeConfig(r io.Reader) (image.Config, error) { + _, c, err := decode(r, true) + return c, err +} + +func init() { + image.RegisterFormat("webp", "RIFF????WEBPVP8", Decode, DecodeConfig) +} -- cgit v1.2.3