src/image/jpeg/writer_test.go - go - Git at Google

 // 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"
 	"math/rand"
 	"os"
 	"strings"
 	"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 := &strings.Builder{}
 		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 TestEncodeYCbCr(t *testing.T) {
 	bo := image.Rect(0, 0, 640, 480)
 	imgRGBA := image.NewRGBA(bo)
 	// Must use 444 subsampling to avoid lossy RGBA to YCbCr conversion.
 	imgYCbCr := image.NewYCbCr(bo, image.YCbCrSubsampleRatio444)
 	rnd := rand.New(rand.NewSource(123))
 	// Create identical rgba and ycbcr images.
 	for y := bo.Min.Y; y < bo.Max.Y; y++ {
 		for x := bo.Min.X; x < bo.Max.X; x++ {
 			col := color.RGBA{
 				uint8(rnd.Intn(256)),
 				uint8(rnd.Intn(256)),
 				uint8(rnd.Intn(256)),
 				255,
 			}
 			imgRGBA.SetRGBA(x, y, col)
 			yo := imgYCbCr.YOffset(x, y)
 			co := imgYCbCr.COffset(x, y)
 			cy, ccr, ccb := color.RGBToYCbCr(col.R, col.G, col.B)
 			imgYCbCr.Y[yo] = cy
 			imgYCbCr.Cb[co] = ccr
 			imgYCbCr.Cr[co] = ccb
 		}
 	}

 	// Now check that both images are identical after an encode.
 	var bufRGBA, bufYCbCr bytes.Buffer
 	Encode(&bufRGBA, imgRGBA, nil)
 	Encode(&bufYCbCr, imgYCbCr, nil)
 	if !bytes.Equal(bufRGBA.Bytes(), bufYCbCr.Bytes()) {
 		t.Errorf("RGBA and YCbCr encoded bytes differ")
 	}
 }

 func BenchmarkEncodeRGBA(b *testing.B) {
 	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.ReportAllocs()
 	b.ResetTimer()
 	options := &Options{Quality: 90}
 	for i := 0; i < b.N; i++ {
 		Encode(io.Discard, img, options)
 	}
 }

 func BenchmarkEncodeYCbCr(b *testing.B) {
 	img := image.NewYCbCr(image.Rect(0, 0, 640, 480), image.YCbCrSubsampleRatio420)
 	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++ {
 			cy := img.YOffset(x, y)
 			ci := img.COffset(x, y)
 			img.Y[cy] = uint8(rnd.Intn(256))
 			img.Cb[ci] = uint8(rnd.Intn(256))
 			img.Cr[ci] = uint8(rnd.Intn(256))
 		}
 	}
 	b.SetBytes(640 * 480 * 3)
 	b.ReportAllocs()
 	b.ResetTimer()
 	options := &Options{Quality: 90}
 	for i := 0; i < b.N; i++ {
 		Encode(io.Discard, img, options)
 	}
 }
	// 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"
	"math/rand"
	"os"
	"strings"
	"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 := &strings.Builder{}
	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 TestEncodeYCbCr(t *testing.T) {
	bo := image.Rect(0, 0, 640, 480)
	imgRGBA := image.NewRGBA(bo)
	// Must use 444 subsampling to avoid lossy RGBA to YCbCr conversion.
	imgYCbCr := image.NewYCbCr(bo, image.YCbCrSubsampleRatio444)
	rnd := rand.New(rand.NewSource(123))
	// Create identical rgba and ycbcr images.
	for y := bo.Min.Y; y < bo.Max.Y; y++ {
	for x := bo.Min.X; x < bo.Max.X; x++ {
	col := color.RGBA{
	uint8(rnd.Intn(256)),
	uint8(rnd.Intn(256)),
	uint8(rnd.Intn(256)),
	255,
	}
	imgRGBA.SetRGBA(x, y, col)
	yo := imgYCbCr.YOffset(x, y)
	co := imgYCbCr.COffset(x, y)
	cy, ccr, ccb := color.RGBToYCbCr(col.R, col.G, col.B)
	imgYCbCr.Y[yo] = cy
	imgYCbCr.Cb[co] = ccr
	imgYCbCr.Cr[co] = ccb
	}
	}

	// Now check that both images are identical after an encode.
	var bufRGBA, bufYCbCr bytes.Buffer
	Encode(&bufRGBA, imgRGBA, nil)
	Encode(&bufYCbCr, imgYCbCr, nil)
	if !bytes.Equal(bufRGBA.Bytes(), bufYCbCr.Bytes()) {
	t.Errorf("RGBA and YCbCr encoded bytes differ")
	}
	}

	func BenchmarkEncodeRGBA(b *testing.B) {
	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.ReportAllocs()
	b.ResetTimer()
	options := &Options{Quality: 90}
	for i := 0; i < b.N; i++ {
	Encode(io.Discard, img, options)
	}
	}

	func BenchmarkEncodeYCbCr(b *testing.B) {
	img := image.NewYCbCr(image.Rect(0, 0, 640, 480), image.YCbCrSubsampleRatio420)
	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++ {
	cy := img.YOffset(x, y)
	ci := img.COffset(x, y)
	img.Y[cy] = uint8(rnd.Intn(256))
	img.Cb[ci] = uint8(rnd.Intn(256))
	img.Cr[ci] = uint8(rnd.Intn(256))
	}
	}
	b.SetBytes(640 * 480 * 3)
	b.ReportAllocs()
	b.ResetTimer()
	options := &Options{Quality: 90}
	for i := 0; i < b.N; i++ {
	Encode(io.Discard, img, options)
	}
	}