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"
 	"reflect"
 	"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 map of 2 pixels), backgroundIndex, aspect
 	paletteStr = "\x10\x20\x30\x40\x50\x60" // the color map, also known as a palette
 	trailerStr = "\x3b"
 )

 // lzwEncode returns an LZW encoding (with 2-bit literals) of n zeroes.
 func lzwEncode(n int) []byte {
 	b := &bytes.Buffer{}
 	w := lzw.NewWriter(b, lzw.LSB, 2)
 	w.Write(make([]byte, n))
 	w.Close()
 	return b.Bytes()
 }

 func TestDecode(t *testing.T) {
 	testCases := []struct {
 		nPix    int  // The number of pixels in the image data.
 		extra   bool // Whether to write an extra block after the LZW-encoded data.
 		wantErr error
 	}{
 		{0, false, errNotEnough},
 		{1, false, errNotEnough},
 		{2, false, nil},
 		{2, true, errTooMuch},
 		{3, false, 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(tc.nPix)
 			if len(enc) > 0xff {
 				t.Errorf("nPix=%d, extra=%t: compressed length %d is too large", tc.nPix, tc.extra, len(enc))
 				continue
 			}
 			b.WriteByte(byte(len(enc)))
 			b.Write(enc)
 		}
 		if tc.extra {
 			b.WriteString("\x01\x02") // A 1-byte payload with an 0x02 byte.
 		}
 		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, extra=%t\ngot  %v\nwant %v", tc.nPix, tc.extra, 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, extra=%t\ngot  %v\nwant %v", tc.nPix, tc.extra, 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\x00\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(2)
 		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 map 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.
 	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.
 	pix := []byte{0, 128}
 	enc := &bytes.Buffer{}
 	w := lzw.NewWriter(enc, lzw.LSB, 2)
 	w.Write(pix)
 	w.Close()
 	b.WriteByte(byte(len(enc.Bytes())))
 	b.Write(enc.Bytes())
 	b.WriteByte(0x00) // An empty block signifies the end of the image data.

 	b.WriteString(trailerStr)

 	try(t, b.Bytes(), "gif: invalid pixel value")
 }

 func TestPixelOutsidePaletteRange(t *testing.T) {
 	for _, pval := range []byte{0, 1, 2, 3, 255} {
 		b := &bytes.Buffer{}

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

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

 		// Encode the pixels; some pvals trigger the expected error.
 		pix := []byte{pval, pval}
 		enc := &bytes.Buffer{}
 		w := lzw.NewWriter(enc, lzw.LSB, 2)
 		w.Write(pix)
 		w.Close()
 		b.WriteByte(byte(len(enc.Bytes())))
 		b.Write(enc.Bytes())
 		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)
 	}
 }
	// 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"
	"reflect"
	"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 map of 2 pixels), backgroundIndex, aspect
	paletteStr = "\x10\x20\x30\x40\x50\x60" // the color map, also known as a palette
	trailerStr = "\x3b"
	)

	// lzwEncode returns an LZW encoding (with 2-bit literals) of n zeroes.
	func lzwEncode(n int) []byte {
	b := &bytes.Buffer{}
	w := lzw.NewWriter(b, lzw.LSB, 2)
	w.Write(make([]byte, n))
	w.Close()
	return b.Bytes()
	}

	func TestDecode(t *testing.T) {
	testCases := []struct {
	nPix int // The number of pixels in the image data.
	extra bool // Whether to write an extra block after the LZW-encoded data.
	wantErr error
	}{
	{0, false, errNotEnough},
	{1, false, errNotEnough},
	{2, false, nil},
	{2, true, errTooMuch},
	{3, false, 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(tc.nPix)
	if len(enc) > 0xff {
	t.Errorf("nPix=%d, extra=%t: compressed length %d is too large", tc.nPix, tc.extra, len(enc))
	continue
	}
	b.WriteByte(byte(len(enc)))
	b.Write(enc)
	}
	if tc.extra {
	b.WriteString("\x01\x02") // A 1-byte payload with an 0x02 byte.
	}
	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, extra=%t\ngot %v\nwant %v", tc.nPix, tc.extra, 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, extra=%t\ngot %v\nwant %v", tc.nPix, tc.extra, 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\x00\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(2)
	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 map 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.
	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.
	pix := []byte{0, 128}
	enc := &bytes.Buffer{}
	w := lzw.NewWriter(enc, lzw.LSB, 2)
	w.Write(pix)
	w.Close()
	b.WriteByte(byte(len(enc.Bytes())))
	b.Write(enc.Bytes())
	b.WriteByte(0x00) // An empty block signifies the end of the image data.

	b.WriteString(trailerStr)

	try(t, b.Bytes(), "gif: invalid pixel value")
	}

	func TestPixelOutsidePaletteRange(t *testing.T) {
	for _, pval := range []byte{0, 1, 2, 3, 255} {
	b := &bytes.Buffer{}

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

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

	// Encode the pixels; some pvals trigger the expected error.
	pix := []byte{pval, pval}
	enc := &bytes.Buffer{}
	w := lzw.NewWriter(enc, lzw.LSB, 2)
	w.Write(pix)
	w.Close()
	b.WriteByte(byte(len(enc.Bytes())))
	b.Write(enc.Bytes())
	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)
	}
	}