summaryrefslogtreecommitdiff
path: root/vendor/golang.org/x/image/webp
diff options
context:
space:
mode:
Diffstat (limited to 'vendor/golang.org/x/image/webp')
-rw-r--r--vendor/golang.org/x/image/webp/decode.go271
-rw-r--r--vendor/golang.org/x/image/webp/doc.go9
2 files changed, 280 insertions, 0 deletions
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 000000000..d6eefd596
--- /dev/null
+++ b/vendor/golang.org/x/image/webp/decode.go
@@ -0,0 +1,271 @@
+// 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.
+
+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
+ )
+ wantAlpha = (buf[0] & alphaBit) != 0
+ 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 {
+ if wantAlpha {
+ return nil, image.Config{
+ ColorModel: color.NYCbCrAModel,
+ Width: int(widthMinusOne) + 1,
+ Height: int(heightMinusOne) + 1,
+ }, nil
+ }
+ return nil, image.Config{
+ ColorModel: color.YCbCrModel,
+ Width: int(widthMinusOne) + 1,
+ Height: int(heightMinusOne) + 1,
+ }, nil
+ }
+ }
+ }
+}
+
+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)
+}
diff --git a/vendor/golang.org/x/image/webp/doc.go b/vendor/golang.org/x/image/webp/doc.go
new file mode 100644
index 000000000..e321c8542
--- /dev/null
+++ b/vendor/golang.org/x/image/webp/doc.go
@@ -0,0 +1,9 @@
+// Copyright 2016 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 webp implements a decoder for WEBP images.
+//
+// WEBP is defined at:
+// https://developers.google.com/speed/webp/docs/riff_container
+package webp // import "golang.org/x/image/webp"
generated by cgit v1.2.3 (git 2.46.0) at 2025-10-31 00:21:23 +0000