Golang程序
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// 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"
"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"
)
// 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) {
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(make([]byte, 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\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) {
data := []byte("GIF89a000\x00000,0\x00\x00\x00\n\x00" +
"\n\x00\x80000000\x02\b\xf01u\xb9\xfdal\x05\x00;")
img, err := DecodeAll(bytes.NewReader(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 != img1.LoopCount {
t.Errorf("loop count mismatch: %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)
}
}
}