1 files changed, 227 insertions, 0 deletions
diff --git a/src/image/gif/writer_test.go b/src/image/gif/writer_test.go
new file mode 100644
index 000000000..93306ffdb
--- /dev/null
+++ b/src/image/gif/writer_test.go
@@ -0,0 +1,227 @@
+// 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"
+	"image"
+	"image/color"
+	_ "image/png"
+	"io/ioutil"
+	"math/rand"
+	"os"
+	"testing"
+)
+
+func readImg(filename string) (image.Image, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	m, _, err := image.Decode(f)
+	return m, err
+}
+
+func readGIF(filename string) (*GIF, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	return DecodeAll(f)
+}
+
+func delta(u0, u1 uint32) int64 {
+	d := int64(u0) - int64(u1)
+	if d < 0 {
+		return -d
+	}
+	return d
+}
+
+// averageDelta returns the average delta in RGB space. The two images must
+// have the same bounds.
+func averageDelta(m0, m1 image.Image) int64 {
+	b := m0.Bounds()
+	var sum, n int64
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		for x := b.Min.X; x < b.Max.X; x++ {
+			c0 := m0.At(x, y)
+			c1 := m1.At(x, y)
+			r0, g0, b0, _ := c0.RGBA()
+			r1, g1, b1, _ := c1.RGBA()
+			sum += delta(r0, r1)
+			sum += delta(g0, g1)
+			sum += delta(b0, b1)
+			n += 3
+		}
+	}
+	return sum / n
+}
+
+var testCase = []struct {
+	filename  string
+	tolerance int64
+}{
+	{"../testdata/video-001.png", 1 << 12},
+	{"../testdata/video-001.gif", 0},
+	{"../testdata/video-001.interlaced.gif", 0},
+}
+
+func TestWriter(t *testing.T) {
+	for _, tc := range testCase {
+		m0, err := readImg(tc.filename)
+		if err != nil {
+			t.Error(tc.filename, err)
+			continue
+		}
+		var buf bytes.Buffer
+		err = Encode(&buf, m0, nil)
+		if err != nil {
+			t.Error(tc.filename, err)
+			continue
+		}
+		m1, err := Decode(&buf)
+		if err != nil {
+			t.Error(tc.filename, err)
+			continue
+		}
+		if m0.Bounds() != m1.Bounds() {
+			t.Errorf("%s, bounds differ: %v and %v", tc.filename, m0.Bounds(), m1.Bounds())
+			continue
+		}
+		// Compare the average delta to the tolerance level.
+		avgDelta := averageDelta(m0, m1)
+		if avgDelta > tc.tolerance {
+			t.Errorf("%s: average delta is too high. expected: %d, got %d", tc.filename, tc.tolerance, avgDelta)
+			continue
+		}
+	}
+}
+
+func TestSubImage(t *testing.T) {
+	m0, err := readImg("../testdata/video-001.gif")
+	if err != nil {
+		t.Fatalf("readImg: %v", err)
+	}
+	m0 = m0.(*image.Paletted).SubImage(image.Rect(0, 0, 50, 30))
+	var buf bytes.Buffer
+	err = Encode(&buf, m0, nil)
+	if err != nil {
+		t.Fatalf("Encode: %v", err)
+	}
+	m1, err := Decode(&buf)
+	if err != nil {
+		t.Fatalf("Decode: %v", err)
+	}
+	if m0.Bounds() != m1.Bounds() {
+		t.Fatalf("bounds differ: %v and %v", m0.Bounds(), m1.Bounds())
+	}
+	if averageDelta(m0, m1) != 0 {
+		t.Fatalf("images differ")
+	}
+}
+
+var frames = []string{
+	"../testdata/video-001.gif",
+	"../testdata/video-005.gray.gif",
+}
+
+func TestEncodeAll(t *testing.T) {
+	g0 := &GIF{
+		Image:     make([]*image.Paletted, len(frames)),
+		Delay:     make([]int, len(frames)),
+		LoopCount: 5,
+	}
+	for i, f := range frames {
+		m, err := readGIF(f)
+		if err != nil {
+			t.Fatal(f, err)
+		}
+		g0.Image[i] = m.Image[0]
+	}
+	var buf bytes.Buffer
+	if err := EncodeAll(&buf, g0); err != nil {
+		t.Fatal("EncodeAll:", err)
+	}
+	g1, err := DecodeAll(&buf)
+	if err != nil {
+		t.Fatal("DecodeAll:", err)
+	}
+	if g0.LoopCount != g1.LoopCount {
+		t.Errorf("loop counts differ: %d and %d", g0.LoopCount, g1.LoopCount)
+	}
+	for i := range g0.Image {
+		m0, m1 := g0.Image[i], g1.Image[i]
+		if m0.Bounds() != m1.Bounds() {
+			t.Errorf("%s, bounds differ: %v and %v", frames[i], m0.Bounds(), m1.Bounds())
+		}
+		d0, d1 := g0.Delay[i], g1.Delay[i]
+		if d0 != d1 {
+			t.Errorf("%s: delay values differ: %d and %d", frames[i], d0, d1)
+		}
+	}
+
+	g1.Delay = make([]int, 1)
+	if err := EncodeAll(ioutil.Discard, g1); err == nil {
+		t.Error("expected error from mismatched delay and image slice lengths")
+	}
+	if err := EncodeAll(ioutil.Discard, &GIF{}); err == nil {
+		t.Error("expected error from providing empty gif")
+	}
+}
+
+func BenchmarkEncode(b *testing.B) {
+	b.StopTimer()
+
+	bo := image.Rect(0, 0, 640, 480)
+	rnd := rand.New(rand.NewSource(123))
+
+	// Restrict to a 256-color paletted image to avoid quantization path.
+	palette := make(color.Palette, 256)
+	for i := range palette {
+		palette[i] = color.RGBA{
+			uint8(rnd.Intn(256)),
+			uint8(rnd.Intn(256)),
+			uint8(rnd.Intn(256)),
+			255,
+		}
+	}
+	img := image.NewPaletted(image.Rect(0, 0, 640, 480), palette)
+	for y := bo.Min.Y; y < bo.Max.Y; y++ {
+		for x := bo.Min.X; x < bo.Max.X; x++ {
+			img.Set(x, y, palette[rnd.Intn(256)])
+		}
+	}
+
+	b.SetBytes(640 * 480 * 4)
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		Encode(ioutil.Discard, img, nil)
+	}
+}
+
+func BenchmarkQuantizedEncode(b *testing.B) {
+	b.StopTimer()
+	img := image.NewRGBA(image.Rect(0, 0, 640, 480))
+	bo := img.Bounds()
+	rnd := rand.New(rand.NewSource(123))
+	for y := bo.Min.Y; y < bo.Max.Y; y++ {
+		for x := bo.Min.X; x < bo.Max.X; x++ {
+			img.SetRGBA(x, y, color.RGBA{
+				uint8(rnd.Intn(256)),
+				uint8(rnd.Intn(256)),
+				uint8(rnd.Intn(256)),
+				255,
+			})
+		}
+	}
+	b.SetBytes(640 * 480 * 4)
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		Encode(ioutil.Discard, img, nil)
+	}
+}