94ba43c478
The blue-purple-pink image comes from http://blog.golang.org/gophercon The tux and yellow_rose images come from https://developers.google.com/speed/webp/gallery2 and according to that page, those images are in the public domain. The gopher-doc images are http://golang.org/doc/gopher/doc.png after quantizing its palette to 2/4/16/256 colors. LGTM=r R=r CC=golang-codereviews https://golang.org/cl/109010043
96 lines
2.3 KiB
Go
96 lines
2.3 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package webp implements a decoder for WEBP images.
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//
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// WEBP is defined at:
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// https://developers.google.com/speed/webp/docs/riff_container
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package webp
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import (
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"errors"
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"image"
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"image/color"
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"io"
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"code.google.com/p/go.image/vp8"
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"code.google.com/p/go.image/vp8l"
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)
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const (
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formatVP8 = 1
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formatVP8L = 2
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)
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func decode(r io.Reader, configOnly bool) (image.Image, image.Config, error) {
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var b [20]byte
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if _, err := io.ReadFull(r, b[:]); err != nil {
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return nil, image.Config{}, err
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}
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format := 0
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switch string(b[8:16]) {
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case "WEBPVP8 ":
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format = formatVP8
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case "WEBPVP8L":
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format = formatVP8L
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}
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if string(b[:4]) != "RIFF" || format == 0 {
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return nil, image.Config{}, errors.New("webp: invalid format")
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}
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riffLen := uint32(b[4]) | uint32(b[5])<<8 | uint32(b[6])<<16 | uint32(b[7])<<24
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dataLen := uint32(b[16]) | uint32(b[17])<<8 | uint32(b[18])<<16 | uint32(b[19])<<24
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if riffLen < dataLen+12 {
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return nil, image.Config{}, errors.New("webp: invalid format")
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}
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if dataLen >= 1<<31 {
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return nil, image.Config{}, errors.New("webp: invalid format")
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}
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if format == formatVP8 {
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d := vp8.NewDecoder()
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d.Init(r, int(dataLen))
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fh, err := d.DecodeFrameHeader()
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if err != nil {
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return nil, image.Config{}, err
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}
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if configOnly {
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return nil, image.Config{
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ColorModel: color.YCbCrModel,
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Width: fh.Width,
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Height: fh.Height,
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}, nil
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}
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m, err := d.DecodeFrame()
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return m, image.Config{}, nil
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}
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r = &io.LimitedReader{r, int64(dataLen)}
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if configOnly {
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c, err := vp8l.DecodeConfig(r)
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return nil, c, err
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}
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m, err := vp8l.Decode(r)
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return m, image.Config{}, err
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}
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// Decode reads a WEBP image from r and returns it as an image.Image.
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func Decode(r io.Reader) (image.Image, error) {
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m, _, err := decode(r, false)
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if err != nil {
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return nil, err
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}
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return m, err
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}
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// DecodeConfig returns the color model and dimensions of a WEBP image without
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// decoding the entire image.
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func DecodeConfig(r io.Reader) (image.Config, error) {
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_, c, err := decode(r, true)
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return c, err
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}
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func init() {
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image.RegisterFormat("webp", "RIFF????WEBPVP8", Decode, DecodeConfig)
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}
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