1 files changed, 120 insertions, 0 deletions
diff --git a/src/image/decode_test.go b/src/image/decode_test.go
new file mode 100644
index 000000000..8dee57ee4
--- /dev/null
+++ b/src/image/decode_test.go
@@ -0,0 +1,120 @@
+// 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 image_test
+
+import (
+	"bufio"
+	"image"
+	"image/color"
+	"os"
+	"testing"
+
+	_ "image/gif"
+	_ "image/jpeg"
+	_ "image/png"
+)
+
+type imageTest struct {
+	goldenFilename string
+	filename       string
+	tolerance      int
+}
+
+var imageTests = []imageTest{
+	{"testdata/video-001.png", "testdata/video-001.png", 0},
+	// GIF images are restricted to a 256-color palette and the conversion
+	// to GIF loses significant image quality.
+	{"testdata/video-001.png", "testdata/video-001.gif", 64 << 8},
+	{"testdata/video-001.png", "testdata/video-001.interlaced.gif", 64 << 8},
+	{"testdata/video-001.png", "testdata/video-001.5bpp.gif", 128 << 8},
+	// JPEG is a lossy format and hence needs a non-zero tolerance.
+	{"testdata/video-001.png", "testdata/video-001.jpeg", 8 << 8},
+	{"testdata/video-001.png", "testdata/video-001.progressive.jpeg", 8 << 8},
+	// Grayscale images.
+	{"testdata/video-005.gray.png", "testdata/video-005.gray.jpeg", 8 << 8},
+	{"testdata/video-005.gray.png", "testdata/video-005.gray.png", 0},
+}
+
+func decode(filename string) (image.Image, string, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, "", err
+	}
+	defer f.Close()
+	return image.Decode(bufio.NewReader(f))
+}
+
+func decodeConfig(filename string) (image.Config, string, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return image.Config{}, "", err
+	}
+	defer f.Close()
+	return image.DecodeConfig(bufio.NewReader(f))
+}
+
+func delta(u0, u1 uint32) int {
+	d := int(u0) - int(u1)
+	if d < 0 {
+		return -d
+	}
+	return d
+}
+
+func withinTolerance(c0, c1 color.Color, tolerance int) bool {
+	r0, g0, b0, a0 := c0.RGBA()
+	r1, g1, b1, a1 := c1.RGBA()
+	r := delta(r0, r1)
+	g := delta(g0, g1)
+	b := delta(b0, b1)
+	a := delta(a0, a1)
+	return r <= tolerance && g <= tolerance && b <= tolerance && a <= tolerance
+}
+
+func TestDecode(t *testing.T) {
+	golden := make(map[string]image.Image)
+loop:
+	for _, it := range imageTests {
+		g := golden[it.goldenFilename]
+		if g == nil {
+			var err error
+			g, _, err = decode(it.goldenFilename)
+			if err != nil {
+				t.Errorf("%s: %v", it.goldenFilename, err)
+				continue loop
+			}
+			golden[it.goldenFilename] = g
+		}
+		m, imageFormat, err := decode(it.filename)
+		if err != nil {
+			t.Errorf("%s: %v", it.filename, err)
+			continue loop
+		}
+		b := g.Bounds()
+		if !b.Eq(m.Bounds()) {
+			t.Errorf("%s: want bounds %v got %v", it.filename, b, m.Bounds())
+			continue loop
+		}
+		for y := b.Min.Y; y < b.Max.Y; y++ {
+			for x := b.Min.X; x < b.Max.X; x++ {
+				if !withinTolerance(g.At(x, y), m.At(x, y), it.tolerance) {
+					t.Errorf("%s: at (%d, %d), want %v got %v", it.filename, x, y, g.At(x, y), m.At(x, y))
+					continue loop
+				}
+			}
+		}
+		if imageFormat == "gif" {
+			// Each frame of a GIF can have a frame-local palette override the
+			// GIF-global palette. Thus, image.Decode can yield a different ColorModel
+			// than image.DecodeConfig.
+			continue
+		}
+		c, _, err := decodeConfig(it.filename)
+		if m.ColorModel() != c.ColorModel {
+			t.Errorf("%s: color models differ", it.filename)
+			continue loop
+		}
+	}
+}