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🎉 完成
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fumiama
365
webp.go
Normal file
365
webp.go
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@@ -0,0 +1,365 @@
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// 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 imgsz
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import (
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"bufio"
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"errors"
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"io"
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"io/ioutil"
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"math"
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)
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var errInvalidFormat = errors.New("webp: invalid format")
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// FourCC is a four character code.
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type FourCC [4]byte
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var (
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fccALPH = FourCC{'A', 'L', 'P', 'H'}
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fccVP8 = FourCC{'V', 'P', '8', ' '}
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fccVP8L = FourCC{'V', 'P', '8', 'L'}
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fccVP8X = FourCC{'V', 'P', '8', 'X'}
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fccWEBP = FourCC{'W', 'E', 'B', 'P'}
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)
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const chunkHeaderSize = 8
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var (
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errMissingPaddingByte = errors.New("riff: missing padding byte")
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errMissingRIFFChunkHeader = errors.New("riff: missing RIFF chunk header")
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errListSubchunkTooLong = errors.New("riff: list subchunk too long")
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errShortChunkData = errors.New("riff: short chunk data")
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errShortChunkHeader = errors.New("riff: short chunk header")
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errStaleReader = errors.New("riff: stale reader")
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)
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// u32 decodes the first four bytes of b as a little-endian integer.
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func u32(b []byte) uint32 {
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return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
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}
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// Reader reads chunks from an underlying io.Reader.
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type Reader struct {
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r io.Reader
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err error
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totalLen uint32
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chunkLen uint32
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chunkReader *chunkReader
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buf [chunkHeaderSize]byte
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padded bool
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}
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// NewListReader returns a LIST chunk's list type, such as "movi" or "wavl",
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// and its chunks as a *Reader.
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func NewListReader(chunkLen uint32, chunkData io.Reader) (listType FourCC, data *Reader, err error) {
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if chunkLen < 4 {
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return FourCC{}, nil, errShortChunkData
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}
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z := &Reader{r: chunkData}
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if _, err := io.ReadFull(chunkData, z.buf[:4]); err != nil {
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if err == io.EOF || err == io.ErrUnexpectedEOF {
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err = errShortChunkData
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}
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return FourCC{}, nil, err
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}
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z.totalLen = chunkLen - 4
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return FourCC{z.buf[0], z.buf[1], z.buf[2], z.buf[3]}, z, nil
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}
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// NewReader returns the RIFF stream's form type, such as "AVI " or "WAVE", and
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// its chunks as a *Reader.
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func NewReader(r io.Reader) (formType FourCC, data *Reader, err error) {
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var buf [chunkHeaderSize]byte
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if _, err := io.ReadFull(r, buf[:]); err != nil {
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if err == io.EOF || err == io.ErrUnexpectedEOF {
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err = errMissingRIFFChunkHeader
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}
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return FourCC{}, nil, err
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}
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if buf[0] != 'R' || buf[1] != 'I' || buf[2] != 'F' || buf[3] != 'F' {
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return FourCC{}, nil, errMissingRIFFChunkHeader
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}
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return NewListReader(u32(buf[4:]), r)
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}
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// Next returns the next chunk's ID, length and data. It returns io.EOF if there
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// are no more chunks. The io.Reader returned becomes stale after the next Next
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// call, and should no longer be used.
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//
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// It is valid to call Next even if all of the previous chunk's data has not
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// been read.
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func (z *Reader) Next() (chunkID FourCC, chunkLen uint32, chunkData io.Reader, err error) {
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if z.err != nil {
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return FourCC{}, 0, nil, z.err
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}
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// Drain the rest of the previous chunk.
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if z.chunkLen != 0 {
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want := z.chunkLen
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var got int64
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got, z.err = io.Copy(ioutil.Discard, z.chunkReader)
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if z.err == nil && uint32(got) != want {
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z.err = errShortChunkData
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}
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if z.err != nil {
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return FourCC{}, 0, nil, z.err
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}
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}
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z.chunkReader = nil
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if z.padded {
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if z.totalLen == 0 {
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z.err = errListSubchunkTooLong
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return FourCC{}, 0, nil, z.err
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}
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z.totalLen--
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_, z.err = io.ReadFull(z.r, z.buf[:1])
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if z.err != nil {
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if z.err == io.EOF {
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z.err = errMissingPaddingByte
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}
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return FourCC{}, 0, nil, z.err
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}
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}
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// We are done if we have no more data.
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if z.totalLen == 0 {
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z.err = io.EOF
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return FourCC{}, 0, nil, z.err
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}
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// Read the next chunk header.
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if z.totalLen < chunkHeaderSize {
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z.err = errShortChunkHeader
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return FourCC{}, 0, nil, z.err
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}
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z.totalLen -= chunkHeaderSize
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if _, z.err = io.ReadFull(z.r, z.buf[:chunkHeaderSize]); z.err != nil {
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if z.err == io.EOF || z.err == io.ErrUnexpectedEOF {
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z.err = errShortChunkHeader
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}
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return FourCC{}, 0, nil, z.err
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}
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chunkID = FourCC{z.buf[0], z.buf[1], z.buf[2], z.buf[3]}
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z.chunkLen = u32(z.buf[4:])
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if z.chunkLen > z.totalLen {
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z.err = errListSubchunkTooLong
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return FourCC{}, 0, nil, z.err
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}
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z.padded = z.chunkLen&1 == 1
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z.chunkReader = &chunkReader{z}
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return chunkID, z.chunkLen, z.chunkReader, nil
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}
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type chunkReader struct {
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z *Reader
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}
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func (c *chunkReader) Read(p []byte) (int, error) {
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if c != c.z.chunkReader {
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return 0, errStaleReader
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}
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z := c.z
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if z.err != nil {
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if z.err == io.EOF {
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return 0, errStaleReader
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}
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return 0, z.err
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}
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n := int(z.chunkLen)
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if n == 0 {
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return 0, io.EOF
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}
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if n < 0 {
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// Converting uint32 to int overflowed.
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n = math.MaxInt32
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}
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if n > len(p) {
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n = len(p)
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}
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n, err := z.r.Read(p[:n])
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z.totalLen -= uint32(n)
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z.chunkLen -= uint32(n)
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if err != io.EOF {
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z.err = err
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}
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return n, err
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}
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func decodewebp(r io.Reader) (Size, error) {
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formType, riffReader, err := NewReader(r)
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if err != nil {
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return Size{}, err
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}
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if formType != fccWEBP {
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return Size{}, errInvalidFormat
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}
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var (
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alpha []byte
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wantAlpha bool
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widthMinusOne uint32
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heightMinusOne uint32
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buf [10]byte
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)
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for {
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chunkID, chunkLen, chunkData, err := riffReader.Next()
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if err == io.EOF {
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err = errInvalidFormat
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}
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if err != nil {
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return Size{}, err
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}
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switch chunkID {
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case fccALPH:
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if !wantAlpha {
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return Size{}, errInvalidFormat
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}
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wantAlpha = false
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// Read the Pre-processing | Filter | Compression byte.
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if _, err := io.ReadFull(chunkData, buf[:1]); err != nil {
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if err == io.EOF {
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err = errInvalidFormat
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}
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return Size{}, err
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}
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case fccVP8:
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if wantAlpha || int32(chunkLen) < 0 {
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return Size{}, errInvalidFormat
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}
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w, h, err := decodeVP8FrameHeader(chunkData)
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if err != nil {
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return Size{}, err
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}
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return Size{w, h}, nil
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case fccVP8L:
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if wantAlpha || alpha != nil {
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return Size{}, errInvalidFormat
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}
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w, h, err := decodeVP8LHeader(chunkData)
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return Size{int(w), int(h)}, err
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case fccVP8X:
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if chunkLen != 10 {
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return Size{}, errInvalidFormat
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}
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if _, err := io.ReadFull(chunkData, buf[:10]); err != nil {
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return Size{}, err
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}
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const (
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animationBit = 1 << 1
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xmpMetadataBit = 1 << 2
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exifMetadataBit = 1 << 3
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alphaBit = 1 << 4
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iccProfileBit = 1 << 5
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)
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wantAlpha = (buf[0] & alphaBit) != 0
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widthMinusOne = uint32(buf[4]) | uint32(buf[5])<<8 | uint32(buf[6])<<16
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heightMinusOne = uint32(buf[7]) | uint32(buf[8])<<8 | uint32(buf[9])<<16
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if wantAlpha {
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return Size{
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Width: int(widthMinusOne) + 1,
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Height: int(heightMinusOne) + 1,
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}, nil
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}
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return Size{
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Width: int(widthMinusOne) + 1,
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Height: int(heightMinusOne) + 1,
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}, nil
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}
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}
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}
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func decodeVP8FrameHeader(r io.Reader) (w, h int, err error) {
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var scratch [8]byte
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// All frame headers are at least 3 bytes long.
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b := scratch[:3]
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if _, err = io.ReadFull(r, b); err != nil {
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return
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}
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if (b[0] & 1) != 0 {
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return 0, 0, nil
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}
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// Frame headers for key frames are an additional 7 bytes long.
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b = scratch[:7]
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if _, err = io.ReadFull(r, b); err != nil {
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return
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}
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// Check the magic sync code.
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if b[0] != 0x9d || b[1] != 0x01 || b[2] != 0x2a {
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err = errors.New("vp8: invalid format")
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return
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}
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return int(b[4]&0x3f)<<8 | int(b[3]), int(b[6]&0x3f)<<8 | int(b[5]), nil
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}
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// vp8ldecoder holds the bit-stream for a VP8L image.
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type vp8ldecoder struct {
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r io.ByteReader
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bits uint32
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nBits uint32
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}
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// read reads the next n bits from the decoder's bit-stream.
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func (d *vp8ldecoder) read(n uint32) (uint32, error) {
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for d.nBits < n {
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c, err := d.r.ReadByte()
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if err != nil {
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if err == io.EOF {
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err = io.ErrUnexpectedEOF
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}
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return 0, err
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}
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d.bits |= uint32(c) << d.nBits
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d.nBits += 8
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}
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u := d.bits & (1<<n - 1)
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d.bits >>= n
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d.nBits -= n
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return u, nil
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}
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func decodeVP8LHeader(r io.Reader) (w int32, h int32, err error) {
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rr, ok := r.(io.ByteReader)
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if !ok {
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rr = bufio.NewReader(r)
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}
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d := &vp8ldecoder{r: rr}
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magic, err := d.read(8)
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if err != nil {
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return 0, 0, err
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}
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if magic != 0x2f {
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return 0, 0, errors.New("vp8l: invalid header")
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}
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width, err := d.read(14)
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if err != nil {
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return 0, 0, err
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}
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width++
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height, err := d.read(14)
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if err != nil {
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return 0, 0, err
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}
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height++
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_, err = d.read(1) // Read and ignore the hasAlpha hint.
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if err != nil {
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return 0, 0, err
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}
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version, err := d.read(3)
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if err != nil {
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return 0, 0, err
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}
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if version != 0 {
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return 0, 0, errors.New("vp8l: invalid version")
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}
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return int32(width), int32(height), nil
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}
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