src/image/gif/reader_test.go - go - Git at Google

 // Copyright 2013 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 gif

 import (
 	"bytes"
 	"compress/lzw"
 	"image"
 	"image/color"
 	"image/color/palette"
 	"io"
 	"io/ioutil"
 	"reflect"
 	"runtime"
 	"runtime/debug"
 	"strings"
 	"testing"
 )

 // header, palette and trailer are parts of a valid 2x1 GIF image.
 const (
 	headerStr = "GIF89a" +
 		"\x02\x00\x01\x00" + // width=2, height=1
 		"\x80\x00\x00" // headerFields=(a color table of 2 pixels), backgroundIndex, aspect
 	paletteStr = "\x10\x20\x30\x40\x50\x60" // the color table, also known as a palette
 	trailerStr = "\x3b"
 )

 // lzw.NewReader wants a io.ByteReader, this ensures we're compatible.
 var _ io.ByteReader = (*blockReader)(nil)

 // lzwEncode returns an LZW encoding (with 2-bit literals) of in.
 func lzwEncode(in []byte) []byte {
 	b := &bytes.Buffer{}
 	w := lzw.NewWriter(b, lzw.LSB, 2)
 	if _, err := w.Write(in); err != nil {
 		panic(err)
 	}
 	if err := w.Close(); err != nil {
 		panic(err)
 	}
 	return b.Bytes()
 }

 func TestDecode(t *testing.T) {
 	// extra contains superfluous bytes to inject into the GIF, either at the end
 	// of an existing data sub-block (past the LZW End of Information code) or in
 	// a separate data sub-block. The 0x02 values are arbitrary.
 	const extra = "\x02\x02\x02\x02"

 	testCases := []struct {
 		nPix int // The number of pixels in the image data.
 		// If non-zero, write this many extra bytes inside the data sub-block
 		// containing the LZW end code.
 		extraExisting int
 		// If non-zero, write an extra block of this many bytes.
 		extraSeparate int
 		wantErr       error
 	}{
 		{0, 0, 0, errNotEnough},
 		{1, 0, 0, errNotEnough},
 		{2, 0, 0, nil},
 		// An extra data sub-block after the compressed section with 1 byte which we
 		// silently skip.
 		{2, 0, 1, nil},
 		// An extra data sub-block after the compressed section with 2 bytes. In
 		// this case we complain that there is too much data.
 		{2, 0, 2, errTooMuch},
 		// Too much pixel data.
 		{3, 0, 0, errTooMuch},
 		// An extra byte after LZW data, but inside the same data sub-block.
 		{2, 1, 0, nil},
 		// Two extra bytes after LZW data, but inside the same data sub-block.
 		{2, 2, 0, nil},
 		// Extra data exists in the final sub-block with LZW data, AND there is
 		// a bogus sub-block following.
 		{2, 1, 1, errTooMuch},
 	}
 	for _, tc := range testCases {
 		b := &bytes.Buffer{}
 		b.WriteString(headerStr)
 		b.WriteString(paletteStr)
 		// Write an image with bounds 2x1 but tc.nPix pixels. If tc.nPix != 2
 		// then this should result in an invalid GIF image. First, write a
 		// magic 0x2c (image descriptor) byte, bounds=(0,0)-(2,1), a flags
 		// byte, and 2-bit LZW literals.
 		b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
 		if tc.nPix > 0 {
 			enc := lzwEncode(make([]byte, tc.nPix))
 			if len(enc)+tc.extraExisting > 0xff {
 				t.Errorf("nPix=%d, extraExisting=%d, extraSeparate=%d: compressed length %d is too large",
 					tc.nPix, tc.extraExisting, tc.extraSeparate, len(enc))
 				continue
 			}

 			// Write the size of the data sub-block containing the LZW data.
 			b.WriteByte(byte(len(enc) + tc.extraExisting))

 			// Write the LZW data.
 			b.Write(enc)

 			// Write extra bytes inside the same data sub-block where LZW data
 			// ended. Each arbitrarily 0x02.
 			b.WriteString(extra[:tc.extraExisting])
 		}

 		if tc.extraSeparate > 0 {
 			// Data sub-block size. This indicates how many extra bytes follow.
 			b.WriteByte(byte(tc.extraSeparate))
 			b.WriteString(extra[:tc.extraSeparate])
 		}
 		b.WriteByte(0x00) // An empty block signifies the end of the image data.
 		b.WriteString(trailerStr)

 		got, err := Decode(b)
 		if err != tc.wantErr {
 			t.Errorf("nPix=%d, extraExisting=%d, extraSeparate=%d\ngot  %v\nwant %v",
 				tc.nPix, tc.extraExisting, tc.extraSeparate, err, tc.wantErr)
 		}

 		if tc.wantErr != nil {
 			continue
 		}
 		want := &image.Paletted{
 			Pix:    []uint8{0, 0},
 			Stride: 2,
 			Rect:   image.Rect(0, 0, 2, 1),
 			Palette: color.Palette{
 				color.RGBA{0x10, 0x20, 0x30, 0xff},
 				color.RGBA{0x40, 0x50, 0x60, 0xff},
 			},
 		}
 		if !reflect.DeepEqual(got, want) {
 			t.Errorf("nPix=%d, extraExisting=%d, extraSeparate=%d\ngot  %v\nwant %v",
 				tc.nPix, tc.extraExisting, tc.extraSeparate, got, want)
 		}
 	}
 }

 func TestTransparentIndex(t *testing.T) {
 	b := &bytes.Buffer{}
 	b.WriteString(headerStr)
 	b.WriteString(paletteStr)
 	for transparentIndex := 0; transparentIndex < 3; transparentIndex++ {
 		if transparentIndex < 2 {
 			// Write the graphic control for the transparent index.
 			b.WriteString("\x21\xf9\x04\x01\x00\x00")
 			b.WriteByte(byte(transparentIndex))
 			b.WriteByte(0)
 		}
 		// Write an image with bounds 2x1, as per TestDecode.
 		b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
 		enc := lzwEncode([]byte{0x00, 0x00})
 		if len(enc) > 0xff {
 			t.Fatalf("compressed length %d is too large", len(enc))
 		}
 		b.WriteByte(byte(len(enc)))
 		b.Write(enc)
 		b.WriteByte(0x00)
 	}
 	b.WriteString(trailerStr)

 	g, err := DecodeAll(b)
 	if err != nil {
 		t.Fatalf("DecodeAll: %v", err)
 	}
 	c0 := color.RGBA{paletteStr[0], paletteStr[1], paletteStr[2], 0xff}
 	c1 := color.RGBA{paletteStr[3], paletteStr[4], paletteStr[5], 0xff}
 	cz := color.RGBA{}
 	wants := []color.Palette{
 		{cz, c1},
 		{c0, cz},
 		{c0, c1},
 	}
 	if len(g.Image) != len(wants) {
 		t.Fatalf("got %d images, want %d", len(g.Image), len(wants))
 	}
 	for i, want := range wants {
 		got := g.Image[i].Palette
 		if !reflect.DeepEqual(got, want) {
 			t.Errorf("palette #%d:\ngot  %v\nwant %v", i, got, want)
 		}
 	}
 }

 // testGIF is a simple GIF that we can modify to test different scenarios.
 var testGIF = []byte{
 	'G', 'I', 'F', '8', '9', 'a',
 	1, 0, 1, 0, // w=1, h=1 (6)
 	128, 0, 0, // headerFields, bg, aspect (10)
 	0, 0, 0, 1, 1, 1, // color table and graphics control (13)
 	0x21, 0xf9, 0x04, 0x00, 0x00, 0x00, 0xff, 0x00, // (19)
 	// frame 1 (0,0 - 1,1)
 	0x2c,
 	0x00, 0x00, 0x00, 0x00,
 	0x01, 0x00, 0x01, 0x00, // (32)
 	0x00,
 	0x02, 0x02, 0x4c, 0x01, 0x00, // lzw pixels
 	// trailer
 	0x3b,
 }

 func try(t *testing.T, b []byte, want string) {
 	_, err := DecodeAll(bytes.NewReader(b))
 	var got string
 	if err != nil {
 		got = err.Error()
 	}
 	if got != want {
 		t.Fatalf("got %v, want %v", got, want)
 	}
 }

 func TestBounds(t *testing.T) {
 	// Make a local copy of testGIF.
 	gif := make([]byte, len(testGIF))
 	copy(gif, testGIF)
 	// Make the bounds too big, just by one.
 	gif[32] = 2
 	want := "gif: frame bounds larger than image bounds"
 	try(t, gif, want)

 	// Make the bounds too small; does not trigger bounds
 	// check, but now there's too much data.
 	gif[32] = 0
 	want = "gif: too much image data"
 	try(t, gif, want)
 	gif[32] = 1

 	// Make the bounds really big, expect an error.
 	want = "gif: frame bounds larger than image bounds"
 	for i := 0; i < 4; i++ {
 		gif[32+i] = 0xff
 	}
 	try(t, gif, want)
 }

 func TestNoPalette(t *testing.T) {
 	b := &bytes.Buffer{}

 	// Manufacture a GIF with no palette, so any pixel at all
 	// will be invalid.
 	b.WriteString(headerStr[:len(headerStr)-3])
 	b.WriteString("\x00\x00\x00") // No global palette.

 	// Image descriptor: 2x1, no local palette, and 2-bit LZW literals.
 	b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")

 	// Encode the pixels: neither is in range, because there is no palette.
 	enc := lzwEncode([]byte{0x00, 0x03})
 	b.WriteByte(byte(len(enc)))
 	b.Write(enc)
 	b.WriteByte(0x00) // An empty block signifies the end of the image data.

 	b.WriteString(trailerStr)

 	try(t, b.Bytes(), "gif: no color table")
 }

 func TestPixelOutsidePaletteRange(t *testing.T) {
 	for _, pval := range []byte{0, 1, 2, 3} {
 		b := &bytes.Buffer{}

 		// Manufacture a GIF with a 2 color palette.
 		b.WriteString(headerStr)
 		b.WriteString(paletteStr)

 		// Image descriptor: 2x1, no local palette, and 2-bit LZW literals.
 		b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")

 		// Encode the pixels; some pvals trigger the expected error.
 		enc := lzwEncode([]byte{pval, pval})
 		b.WriteByte(byte(len(enc)))
 		b.Write(enc)
 		b.WriteByte(0x00) // An empty block signifies the end of the image data.

 		b.WriteString(trailerStr)

 		// No error expected, unless the pixels are beyond the 2 color palette.
 		want := ""
 		if pval >= 2 {
 			want = "gif: invalid pixel value"
 		}
 		try(t, b.Bytes(), want)
 	}
 }

 func TestTransparentPixelOutsidePaletteRange(t *testing.T) {
 	b := &bytes.Buffer{}

 	// Manufacture a GIF with a 2 color palette.
 	b.WriteString(headerStr)
 	b.WriteString(paletteStr)

 	// Graphic Control Extension: transparency, transparent color index = 3.
 	//
 	// This index, 3, is out of range of the global palette and there is no
 	// local palette in the subsequent image descriptor. This is an error
 	// according to the spec, but Firefox and Google Chrome seem OK with this.
 	//
 	// See golang.org/issue/15059.
 	b.WriteString("\x21\xf9\x04\x01\x00\x00\x03\x00")

 	// Image descriptor: 2x1, no local palette, and 2-bit LZW literals.
 	b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")

 	// Encode the pixels.
 	enc := lzwEncode([]byte{0x03, 0x03})
 	b.WriteByte(byte(len(enc)))
 	b.Write(enc)
 	b.WriteByte(0x00) // An empty block signifies the end of the image data.

 	b.WriteString(trailerStr)

 	try(t, b.Bytes(), "")
 }

 func TestLoopCount(t *testing.T) {
 	testCases := []struct {
 		name      string
 		data      []byte
 		loopCount int
 	}{
 		{
 			"loopcount-missing",
 			[]byte("GIF89a000\x00000" +
 				",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 0 descriptor & color table
 				"\x02\b\xf01u\xb9\xfdal\x05\x00;"), // image 0 image data & trailer
 			-1,
 		},
 		{
 			"loopcount-0",
 			[]byte("GIF89a000\x00000" +
 				"!\xff\vNETSCAPE2.0\x03\x01\x00\x00\x00" + // loop count = 0
 				",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 0 descriptor & color table
 				"\x02\b\xf01u\xb9\xfdal\x05\x00" + // image 0 image data
 				",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 1 descriptor & color table
 				"\x02\b\xf01u\xb9\xfdal\x05\x00;"), // image 1 image data & trailer
 			0,
 		},
 		{
 			"loopcount-1",
 			[]byte("GIF89a000\x00000" +
 				"!\xff\vNETSCAPE2.0\x03\x01\x01\x00\x00" + // loop count = 1
 				",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 0 descriptor & color table
 				"\x02\b\xf01u\xb9\xfdal\x05\x00" + // image 0 image data
 				",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 1 descriptor & color table
 				"\x02\b\xf01u\xb9\xfdal\x05\x00;"), // image 1 image data & trailer
 			1,
 		},
 	}

 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
 			img, err := DecodeAll(bytes.NewReader(tc.data))
 			if err != nil {
 				t.Fatal("DecodeAll:", err)
 			}
 			w := new(bytes.Buffer)
 			err = EncodeAll(w, img)
 			if err != nil {
 				t.Fatal("EncodeAll:", err)
 			}
 			img1, err := DecodeAll(w)
 			if err != nil {
 				t.Fatal("DecodeAll:", err)
 			}
 			if img.LoopCount != tc.loopCount {
 				t.Errorf("loop count mismatch: %d vs %d", img.LoopCount, tc.loopCount)
 			}
 			if img.LoopCount != img1.LoopCount {
 				t.Errorf("loop count failed round-trip: %d vs %d", img.LoopCount, img1.LoopCount)
 			}
 		})
 	}
 }

 func TestUnexpectedEOF(t *testing.T) {
 	for i := len(testGIF) - 1; i >= 0; i-- {
 		_, err := Decode(bytes.NewReader(testGIF[:i]))
 		if err == errNotEnough {
 			continue
 		}
 		text := ""
 		if err != nil {
 			text = err.Error()
 		}
 		if !strings.HasPrefix(text, "gif:") || !strings.HasSuffix(text, ": unexpected EOF") {
 			t.Errorf("Decode(testGIF[:%d]) = %v, want gif: ...: unexpected EOF", i, err)
 		}
 	}
 }

 // See golang.org/issue/22237
 func TestDecodeMemoryConsumption(t *testing.T) {
 	const frames = 3000
 	img := image.NewPaletted(image.Rectangle{Max: image.Point{1, 1}}, palette.WebSafe)
 	hugeGIF := &GIF{
 		Image:    make([]*image.Paletted, frames),
 		Delay:    make([]int, frames),
 		Disposal: make([]byte, frames),
 	}
 	for i := 0; i < frames; i++ {
 		hugeGIF.Image[i] = img
 		hugeGIF.Delay[i] = 60
 	}
 	buf := new(bytes.Buffer)
 	if err := EncodeAll(buf, hugeGIF); err != nil {
 		t.Fatal("EncodeAll:", err)
 	}
 	s0, s1 := new(runtime.MemStats), new(runtime.MemStats)
 	runtime.GC()
 	defer debug.SetGCPercent(debug.SetGCPercent(5))
 	runtime.ReadMemStats(s0)
 	if _, err := Decode(buf); err != nil {
 		t.Fatal("Decode:", err)
 	}
 	runtime.ReadMemStats(s1)
 	if heapDiff := int64(s1.HeapAlloc - s0.HeapAlloc); heapDiff > 30<<20 {
 		t.Fatalf("Decode of %d frames increased heap by %dMB", frames, heapDiff>>20)
 	}
 }

 func BenchmarkDecode(b *testing.B) {
 	data, err := ioutil.ReadFile("../testdata/video-001.gif")
 	if err != nil {
 		b.Fatal(err)
 	}
 	cfg, err := DecodeConfig(bytes.NewReader(data))
 	if err != nil {
 		b.Fatal(err)
 	}
 	b.SetBytes(int64(cfg.Width * cfg.Height))
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		Decode(bytes.NewReader(data))
 	}
 }
	// Copyright 2013 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 gif

	import (
	"bytes"
	"compress/lzw"
	"image"
	"image/color"
	"image/color/palette"
	"io"
	"io/ioutil"
	"reflect"
	"runtime"
	"runtime/debug"
	"strings"
	"testing"
	)

	// header, palette and trailer are parts of a valid 2x1 GIF image.
	const (
	headerStr = "GIF89a" +
	"\x02\x00\x01\x00" + // width=2, height=1
	"\x80\x00\x00" // headerFields=(a color table of 2 pixels), backgroundIndex, aspect
	paletteStr = "\x10\x20\x30\x40\x50\x60" // the color table, also known as a palette
	trailerStr = "\x3b"
	)

	// lzw.NewReader wants a io.ByteReader, this ensures we're compatible.
	var _ io.ByteReader = (*blockReader)(nil)

	// lzwEncode returns an LZW encoding (with 2-bit literals) of in.
	func lzwEncode(in []byte) []byte {
	b := &bytes.Buffer{}
	w := lzw.NewWriter(b, lzw.LSB, 2)
	if _, err := w.Write(in); err != nil {
	panic(err)
	}
	if err := w.Close(); err != nil {
	panic(err)
	}
	return b.Bytes()
	}

	func TestDecode(t *testing.T) {
	// extra contains superfluous bytes to inject into the GIF, either at the end
	// of an existing data sub-block (past the LZW End of Information code) or in
	// a separate data sub-block. The 0x02 values are arbitrary.
	const extra = "\x02\x02\x02\x02"

	testCases := []struct {
	nPix int // The number of pixels in the image data.
	// If non-zero, write this many extra bytes inside the data sub-block
	// containing the LZW end code.
	extraExisting int
	// If non-zero, write an extra block of this many bytes.
	extraSeparate int
	wantErr error
	}{
	{0, 0, 0, errNotEnough},
	{1, 0, 0, errNotEnough},
	{2, 0, 0, nil},
	// An extra data sub-block after the compressed section with 1 byte which we
	// silently skip.
	{2, 0, 1, nil},
	// An extra data sub-block after the compressed section with 2 bytes. In
	// this case we complain that there is too much data.
	{2, 0, 2, errTooMuch},
	// Too much pixel data.
	{3, 0, 0, errTooMuch},
	// An extra byte after LZW data, but inside the same data sub-block.
	{2, 1, 0, nil},
	// Two extra bytes after LZW data, but inside the same data sub-block.
	{2, 2, 0, nil},
	// Extra data exists in the final sub-block with LZW data, AND there is
	// a bogus sub-block following.
	{2, 1, 1, errTooMuch},
	}
	for _, tc := range testCases {
	b := &bytes.Buffer{}
	b.WriteString(headerStr)
	b.WriteString(paletteStr)
	// Write an image with bounds 2x1 but tc.nPix pixels. If tc.nPix != 2
	// then this should result in an invalid GIF image. First, write a
	// magic 0x2c (image descriptor) byte, bounds=(0,0)-(2,1), a flags
	// byte, and 2-bit LZW literals.
	b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
	if tc.nPix > 0 {
	enc := lzwEncode(make([]byte, tc.nPix))
	if len(enc)+tc.extraExisting > 0xff {
	t.Errorf("nPix=%d, extraExisting=%d, extraSeparate=%d: compressed length %d is too large",
	tc.nPix, tc.extraExisting, tc.extraSeparate, len(enc))
	continue
	}

	// Write the size of the data sub-block containing the LZW data.
	b.WriteByte(byte(len(enc) + tc.extraExisting))

	// Write the LZW data.
	b.Write(enc)

	// Write extra bytes inside the same data sub-block where LZW data
	// ended. Each arbitrarily 0x02.
	b.WriteString(extra[:tc.extraExisting])
	}

	if tc.extraSeparate > 0 {
	// Data sub-block size. This indicates how many extra bytes follow.
	b.WriteByte(byte(tc.extraSeparate))
	b.WriteString(extra[:tc.extraSeparate])
	}
	b.WriteByte(0x00) // An empty block signifies the end of the image data.
	b.WriteString(trailerStr)

	got, err := Decode(b)
	if err != tc.wantErr {
	t.Errorf("nPix=%d, extraExisting=%d, extraSeparate=%d\ngot %v\nwant %v",
	tc.nPix, tc.extraExisting, tc.extraSeparate, err, tc.wantErr)
	}

	if tc.wantErr != nil {
	continue
	}
	want := &image.Paletted{
	Pix: []uint8{0, 0},
	Stride: 2,
	Rect: image.Rect(0, 0, 2, 1),
	Palette: color.Palette{
	color.RGBA{0x10, 0x20, 0x30, 0xff},
	color.RGBA{0x40, 0x50, 0x60, 0xff},
	},
	}
	if !reflect.DeepEqual(got, want) {
	t.Errorf("nPix=%d, extraExisting=%d, extraSeparate=%d\ngot %v\nwant %v",
	tc.nPix, tc.extraExisting, tc.extraSeparate, got, want)
	}
	}
	}

	func TestTransparentIndex(t *testing.T) {
	b := &bytes.Buffer{}
	b.WriteString(headerStr)
	b.WriteString(paletteStr)
	for transparentIndex := 0; transparentIndex < 3; transparentIndex++ {
	if transparentIndex < 2 {
	// Write the graphic control for the transparent index.
	b.WriteString("\x21\xf9\x04\x01\x00\x00")
	b.WriteByte(byte(transparentIndex))
	b.WriteByte(0)
	}
	// Write an image with bounds 2x1, as per TestDecode.
	b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
	enc := lzwEncode([]byte{0x00, 0x00})
	if len(enc) > 0xff {
	t.Fatalf("compressed length %d is too large", len(enc))
	}
	b.WriteByte(byte(len(enc)))
	b.Write(enc)
	b.WriteByte(0x00)
	}
	b.WriteString(trailerStr)

	g, err := DecodeAll(b)
	if err != nil {
	t.Fatalf("DecodeAll: %v", err)
	}
	c0 := color.RGBA{paletteStr[0], paletteStr[1], paletteStr[2], 0xff}
	c1 := color.RGBA{paletteStr[3], paletteStr[4], paletteStr[5], 0xff}
	cz := color.RGBA{}
	wants := []color.Palette{
	{cz, c1},
	{c0, cz},
	{c0, c1},
	}
	if len(g.Image) != len(wants) {
	t.Fatalf("got %d images, want %d", len(g.Image), len(wants))
	}
	for i, want := range wants {
	got := g.Image[i].Palette
	if !reflect.DeepEqual(got, want) {
	t.Errorf("palette #%d:\ngot %v\nwant %v", i, got, want)
	}
	}
	}

	// testGIF is a simple GIF that we can modify to test different scenarios.
	var testGIF = []byte{
	'G', 'I', 'F', '8', '9', 'a',
	1, 0, 1, 0, // w=1, h=1 (6)
	128, 0, 0, // headerFields, bg, aspect (10)
	0, 0, 0, 1, 1, 1, // color table and graphics control (13)
	0x21, 0xf9, 0x04, 0x00, 0x00, 0x00, 0xff, 0x00, // (19)
	// frame 1 (0,0 - 1,1)
	0x2c,
	0x00, 0x00, 0x00, 0x00,
	0x01, 0x00, 0x01, 0x00, // (32)
	0x00,
	0x02, 0x02, 0x4c, 0x01, 0x00, // lzw pixels
	// trailer
	0x3b,
	}

	func try(t *testing.T, b []byte, want string) {
	_, err := DecodeAll(bytes.NewReader(b))
	var got string
	if err != nil {
	got = err.Error()
	}
	if got != want {
	t.Fatalf("got %v, want %v", got, want)
	}
	}

	func TestBounds(t *testing.T) {
	// Make a local copy of testGIF.
	gif := make([]byte, len(testGIF))
	copy(gif, testGIF)
	// Make the bounds too big, just by one.
	gif[32] = 2
	want := "gif: frame bounds larger than image bounds"
	try(t, gif, want)

	// Make the bounds too small; does not trigger bounds
	// check, but now there's too much data.
	gif[32] = 0
	want = "gif: too much image data"
	try(t, gif, want)
	gif[32] = 1

	// Make the bounds really big, expect an error.
	want = "gif: frame bounds larger than image bounds"
	for i := 0; i < 4; i++ {
	gif[32+i] = 0xff
	}
	try(t, gif, want)
	}

	func TestNoPalette(t *testing.T) {
	b := &bytes.Buffer{}

	// Manufacture a GIF with no palette, so any pixel at all
	// will be invalid.
	b.WriteString(headerStr[:len(headerStr)-3])
	b.WriteString("\x00\x00\x00") // No global palette.

	// Image descriptor: 2x1, no local palette, and 2-bit LZW literals.
	b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")

	// Encode the pixels: neither is in range, because there is no palette.
	enc := lzwEncode([]byte{0x00, 0x03})
	b.WriteByte(byte(len(enc)))
	b.Write(enc)
	b.WriteByte(0x00) // An empty block signifies the end of the image data.

	b.WriteString(trailerStr)

	try(t, b.Bytes(), "gif: no color table")
	}

	func TestPixelOutsidePaletteRange(t *testing.T) {
	for _, pval := range []byte{0, 1, 2, 3} {
	b := &bytes.Buffer{}

	// Manufacture a GIF with a 2 color palette.
	b.WriteString(headerStr)
	b.WriteString(paletteStr)

	// Image descriptor: 2x1, no local palette, and 2-bit LZW literals.
	b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")

	// Encode the pixels; some pvals trigger the expected error.
	enc := lzwEncode([]byte{pval, pval})
	b.WriteByte(byte(len(enc)))
	b.Write(enc)
	b.WriteByte(0x00) // An empty block signifies the end of the image data.

	b.WriteString(trailerStr)

	// No error expected, unless the pixels are beyond the 2 color palette.
	want := ""
	if pval >= 2 {
	want = "gif: invalid pixel value"
	}
	try(t, b.Bytes(), want)
	}
	}

	func TestTransparentPixelOutsidePaletteRange(t *testing.T) {
	b := &bytes.Buffer{}

	// Manufacture a GIF with a 2 color palette.
	b.WriteString(headerStr)
	b.WriteString(paletteStr)

	// Graphic Control Extension: transparency, transparent color index = 3.
	//
	// This index, 3, is out of range of the global palette and there is no
	// local palette in the subsequent image descriptor. This is an error
	// according to the spec, but Firefox and Google Chrome seem OK with this.
	//
	// See golang.org/issue/15059.
	b.WriteString("\x21\xf9\x04\x01\x00\x00\x03\x00")

	// Image descriptor: 2x1, no local palette, and 2-bit LZW literals.
	b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")

	// Encode the pixels.
	enc := lzwEncode([]byte{0x03, 0x03})
	b.WriteByte(byte(len(enc)))
	b.Write(enc)
	b.WriteByte(0x00) // An empty block signifies the end of the image data.

	b.WriteString(trailerStr)

	try(t, b.Bytes(), "")
	}

	func TestLoopCount(t *testing.T) {
	testCases := []struct {
	name string
	data []byte
	loopCount int
	}{
	{
	"loopcount-missing",
	[]byte("GIF89a000\x00000" +
	",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 0 descriptor & color table
	"\x02\b\xf01u\xb9\xfdal\x05\x00;"), // image 0 image data & trailer
	-1,
	},
	{
	"loopcount-0",
	[]byte("GIF89a000\x00000" +
	"!\xff\vNETSCAPE2.0\x03\x01\x00\x00\x00" + // loop count = 0
	",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 0 descriptor & color table
	"\x02\b\xf01u\xb9\xfdal\x05\x00" + // image 0 image data
	",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 1 descriptor & color table
	"\x02\b\xf01u\xb9\xfdal\x05\x00;"), // image 1 image data & trailer
	0,
	},
	{
	"loopcount-1",
	[]byte("GIF89a000\x00000" +
	"!\xff\vNETSCAPE2.0\x03\x01\x01\x00\x00" + // loop count = 1
	",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 0 descriptor & color table
	"\x02\b\xf01u\xb9\xfdal\x05\x00" + // image 0 image data
	",0\x00\x00\x00\n\x00\n\x00\x80000000" + // image 1 descriptor & color table
	"\x02\b\xf01u\xb9\xfdal\x05\x00;"), // image 1 image data & trailer
	1,
	},
	}

	for _, tc := range testCases {
	t.Run(tc.name, func(t *testing.T) {
	img, err := DecodeAll(bytes.NewReader(tc.data))
	if err != nil {
	t.Fatal("DecodeAll:", err)
	}
	w := new(bytes.Buffer)
	err = EncodeAll(w, img)
	if err != nil {
	t.Fatal("EncodeAll:", err)
	}
	img1, err := DecodeAll(w)
	if err != nil {
	t.Fatal("DecodeAll:", err)
	}
	if img.LoopCount != tc.loopCount {
	t.Errorf("loop count mismatch: %d vs %d", img.LoopCount, tc.loopCount)
	}
	if img.LoopCount != img1.LoopCount {
	t.Errorf("loop count failed round-trip: %d vs %d", img.LoopCount, img1.LoopCount)
	}
	})
	}
	}

	func TestUnexpectedEOF(t *testing.T) {
	for i := len(testGIF) - 1; i >= 0; i-- {
	_, err := Decode(bytes.NewReader(testGIF[:i]))
	if err == errNotEnough {
	continue
	}
	text := ""
	if err != nil {
	text = err.Error()
	}
	if !strings.HasPrefix(text, "gif:") \|\| !strings.HasSuffix(text, ": unexpected EOF") {
	t.Errorf("Decode(testGIF[:%d]) = %v, want gif: ...: unexpected EOF", i, err)
	}
	}
	}

	// See golang.org/issue/22237
	func TestDecodeMemoryConsumption(t *testing.T) {
	const frames = 3000
	img := image.NewPaletted(image.Rectangle{Max: image.Point{1, 1}}, palette.WebSafe)
	hugeGIF := &GIF{
	Image: make([]*image.Paletted, frames),
	Delay: make([]int, frames),
	Disposal: make([]byte, frames),
	}
	for i := 0; i < frames; i++ {
	hugeGIF.Image[i] = img
	hugeGIF.Delay[i] = 60
	}
	buf := new(bytes.Buffer)
	if err := EncodeAll(buf, hugeGIF); err != nil {
	t.Fatal("EncodeAll:", err)
	}
	s0, s1 := new(runtime.MemStats), new(runtime.MemStats)
	runtime.GC()
	defer debug.SetGCPercent(debug.SetGCPercent(5))
	runtime.ReadMemStats(s0)
	if _, err := Decode(buf); err != nil {
	t.Fatal("Decode:", err)
	}
	runtime.ReadMemStats(s1)
	if heapDiff := int64(s1.HeapAlloc - s0.HeapAlloc); heapDiff > 30<<20 {
	t.Fatalf("Decode of %d frames increased heap by %dMB", frames, heapDiff>>20)
	}
	}

	func BenchmarkDecode(b *testing.B) {
	data, err := ioutil.ReadFile("../testdata/video-001.gif")
	if err != nil {
	b.Fatal(err)
	}
	cfg, err := DecodeConfig(bytes.NewReader(data))
	if err != nil {
	b.Fatal(err)
	}
	b.SetBytes(int64(cfg.Width * cfg.Height))
	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
	Decode(bytes.NewReader(data))
	}
	}