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// 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 jpeg
import (
"bytes"
"fmt"
"image"
"image/color"
"image/png"
"io/ioutil"
"math/rand"
"os"
"testing"
)
// zigzag maps from the natural ordering to the zig-zag ordering. For example,
// zigzag[0*8 + 3] is the zig-zag sequence number of the element in the fourth
// column and first row.
var zigzag = [blockSize]int{
0, 1, 5, 6, 14, 15, 27, 28,
2, 4, 7, 13, 16, 26, 29, 42,
3, 8, 12, 17, 25, 30, 41, 43,
9, 11, 18, 24, 31, 40, 44, 53,
10, 19, 23, 32, 39, 45, 52, 54,
20, 22, 33, 38, 46, 51, 55, 60,
21, 34, 37, 47, 50, 56, 59, 61,
35, 36, 48, 49, 57, 58, 62, 63,
}
func TestZigUnzig(t *testing.T) {
for i := 0; i < blockSize; i++ {
if unzig[zigzag[i]] != i {
t.Errorf("unzig[zigzag[%d]] == %d", i, unzig[zigzag[i]])
}
if zigzag[unzig[i]] != i {
t.Errorf("zigzag[unzig[%d]] == %d", i, zigzag[unzig[i]])
}
}
}
// unscaledQuantInNaturalOrder are the unscaled quantization tables in
// natural (not zig-zag) order, as specified in section K.1.
var unscaledQuantInNaturalOrder = [nQuantIndex][blockSize]byte{
// Luminance.
{
16, 11, 10, 16, 24, 40, 51, 61,
12, 12, 14, 19, 26, 58, 60, 55,
14, 13, 16, 24, 40, 57, 69, 56,
14, 17, 22, 29, 51, 87, 80, 62,
18, 22, 37, 56, 68, 109, 103, 77,
24, 35, 55, 64, 81, 104, 113, 92,
49, 64, 78, 87, 103, 121, 120, 101,
72, 92, 95, 98, 112, 100, 103, 99,
},
// Chrominance.
{
17, 18, 24, 47, 99, 99, 99, 99,
18, 21, 26, 66, 99, 99, 99, 99,
24, 26, 56, 99, 99, 99, 99, 99,
47, 66, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
},
}
func TestUnscaledQuant(t *testing.T) {
bad := false
for i := quantIndex(0); i < nQuantIndex; i++ {
for zig := 0; zig < blockSize; zig++ {
got := unscaledQuant[i][zig]
want := unscaledQuantInNaturalOrder[i][unzig[zig]]
if got != want {
t.Errorf("i=%d, zig=%d: got %d, want %d", i, zig, got, want)
bad = true
}
}
}
if bad {
names := [nQuantIndex]string{"Luminance", "Chrominance"}
buf := &bytes.Buffer{}
for i, name := range names {
fmt.Fprintf(buf, "// %s.\n{\n", name)
for zig := 0; zig < blockSize; zig++ {
fmt.Fprintf(buf, "%d, ", unscaledQuantInNaturalOrder[i][unzig[zig]])
if zig%8 == 7 {
buf.WriteString("\n")
}
}
buf.WriteString("},\n")
}
t.Logf("expected unscaledQuant values:\n%s", buf.String())
}
}
var testCase = []struct {
filename string
quality int
tolerance int64
}{
{"../testdata/video-001.png", 1, 24 << 8},
{"../testdata/video-001.png", 20, 12 << 8},
{"../testdata/video-001.png", 60, 8 << 8},
{"../testdata/video-001.png", 80, 6 << 8},
{"../testdata/video-001.png", 90, 4 << 8},
{"../testdata/video-001.png", 100, 2 << 8},
}
func delta(u0, u1 uint32) int64 {
d := int64(u0) - int64(u1)
if d < 0 {
return -d
}
return d
}
func readPng(filename string) (image.Image, error) {
f, err := os.Open(filename)
if err != nil {
return nil, err
}
defer f.Close()
return png.Decode(f)
}
func TestWriter(t *testing.T) {
for _, tc := range testCase {
// Read the image.
m0, err := readPng(tc.filename)
if err != nil {
t.Error(tc.filename, err)
continue
}
// Encode that image as JPEG.
var buf bytes.Buffer
err = Encode(&buf, m0, &Options{Quality: tc.quality})
if err != nil {
t.Error(tc.filename, err)
continue
}
// Decode that JPEG.
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.
if averageDelta(m0, m1) > tc.tolerance {
t.Errorf("%s, quality=%d: average delta is too high", tc.filename, tc.quality)
continue
}
}
}
// TestWriteGrayscale tests that a grayscale images survives a round-trip
// through encode/decode cycle.
func TestWriteGrayscale(t *testing.T) {
m0 := image.NewGray(image.Rect(0, 0, 32, 32))
for i := range m0.Pix {
m0.Pix[i] = uint8(i)
}
var buf bytes.Buffer
if err := Encode(&buf, m0, nil); err != nil {
t.Fatal(err)
}
m1, err := Decode(&buf)
if err != nil {
t.Fatal(err)
}
if m0.Bounds() != m1.Bounds() {
t.Fatalf("bounds differ: %v and %v", m0.Bounds(), m1.Bounds())
}
if _, ok := m1.(*image.Gray); !ok {
t.Errorf("got %T, want *image.Gray", m1)
}
// Compare the average delta to the tolerance level.
want := int64(2 << 8)
if got := averageDelta(m0, m1); got > want {
t.Errorf("average delta too high; got %d, want <= %d", got, want)
}
}
// 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
}
func BenchmarkEncode(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()
options := &Options{Quality: 90}
for i := 0; i < b.N; i++ {
Encode(ioutil.Discard, img, options)
}
}
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