Adding upstream version 1.17.13.upstream/1.17.13upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 299 insertions, 0 deletions

diff --git a/src/image/jpeg/dct_test.go b/src/image/jpeg/dct_test.go
new file mode 100644
index 0000000..845e758
--- /dev/null
+++ b/src/image/jpeg/dct_test.go
@@ -0,0 +1,299 @@
+// Copyright 2012 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"
+	"math"
+	"math/rand"
+	"testing"
+)
+
+func benchmarkDCT(b *testing.B, f func(*block)) {
+	b.StopTimer()
+	blocks := make([]block, 0, b.N*len(testBlocks))
+	for i := 0; i < b.N; i++ {
+		blocks = append(blocks, testBlocks[:]...)
+	}
+	b.StartTimer()
+	for i := range blocks {
+		f(&blocks[i])
+	}
+}
+
+func BenchmarkFDCT(b *testing.B) {
+	benchmarkDCT(b, fdct)
+}
+
+func BenchmarkIDCT(b *testing.B) {
+	benchmarkDCT(b, idct)
+}
+
+func TestDCT(t *testing.T) {
+	blocks := make([]block, len(testBlocks))
+	copy(blocks, testBlocks[:])
+
+	// Append some randomly generated blocks of varying sparseness.
+	r := rand.New(rand.NewSource(123))
+	for i := 0; i < 100; i++ {
+		b := block{}
+		n := r.Int() % 64
+		for j := 0; j < n; j++ {
+			b[r.Int()%len(b)] = r.Int31() % 256
+		}
+		blocks = append(blocks, b)
+	}
+
+	// Check that the FDCT and IDCT functions are inverses, after a scale and
+	// level shift. Scaling reduces the rounding errors in the conversion from
+	// floats to ints.
+	for i, b := range blocks {
+		got, want := b, b
+		for j := range got {
+			got[j] = (got[j] - 128) * 8
+		}
+		slowFDCT(&got)
+		slowIDCT(&got)
+		for j := range got {
+			got[j] = got[j]/8 + 128
+		}
+		if differ(&got, &want) {
+			t.Errorf("i=%d: IDCT(FDCT)\nsrc\n%s\ngot\n%s\nwant\n%s\n", i, &b, &got, &want)
+		}
+	}
+
+	// Check that the optimized and slow FDCT implementations agree.
+	// The fdct function already does a scale and level shift.
+	for i, b := range blocks {
+		got, want := b, b
+		fdct(&got)
+		for j := range want {
+			want[j] = (want[j] - 128) * 8
+		}
+		slowFDCT(&want)
+		if differ(&got, &want) {
+			t.Errorf("i=%d: FDCT\nsrc\n%s\ngot\n%s\nwant\n%s\n", i, &b, &got, &want)
+		}
+	}
+
+	// Check that the optimized and slow IDCT implementations agree.
+	for i, b := range blocks {
+		got, want := b, b
+		idct(&got)
+		slowIDCT(&want)
+		if differ(&got, &want) {
+			t.Errorf("i=%d: IDCT\nsrc\n%s\ngot\n%s\nwant\n%s\n", i, &b, &got, &want)
+		}
+	}
+}
+
+// differ reports whether any pair-wise elements in b0 and b1 differ by 2 or
+// more. That tolerance is because there isn't a single definitive decoding of
+// a given JPEG image, even before the YCbCr to RGB conversion; implementations
+// can have different IDCT rounding errors.
+func differ(b0, b1 *block) bool {
+	for i := range b0 {
+		delta := b0[i] - b1[i]
+		if delta < -2 || +2 < delta {
+			return true
+		}
+	}
+	return false
+}
+
+// alpha returns 1 if i is 0 and returns √2 otherwise.
+func alpha(i int) float64 {
+	if i == 0 {
+		return 1
+	}
+	return math.Sqrt2
+}
+
+var cosines [32]float64 // cosines[k] = cos(π/2 * k/8)
+
+func init() {
+	for k := range cosines {
+		cosines[k] = math.Cos(math.Pi * float64(k) / 16)
+	}
+}
+
+// slowFDCT performs the 8*8 2-dimensional forward discrete cosine transform:
+//
+//	dst[u,v] = (1/8) * Σ_x Σ_y alpha(u) * alpha(v) * src[x,y] *
+//		cos((π/2) * (2*x + 1) * u / 8) *
+//		cos((π/2) * (2*y + 1) * v / 8)
+//
+// x and y are in pixel space, and u and v are in transform space.
+//
+// b acts as both dst and src.
+func slowFDCT(b *block) {
+	var dst [blockSize]float64
+	for v := 0; v < 8; v++ {
+		for u := 0; u < 8; u++ {
+			sum := 0.0
+			for y := 0; y < 8; y++ {
+				for x := 0; x < 8; x++ {
+					sum += alpha(u) * alpha(v) * float64(b[8*y+x]) *
+						cosines[((2*x+1)*u)%32] *
+						cosines[((2*y+1)*v)%32]
+				}
+			}
+			dst[8*v+u] = sum / 8
+		}
+	}
+	// Convert from float64 to int32.
+	for i := range dst {
+		b[i] = int32(dst[i] + 0.5)
+	}
+}
+
+// slowIDCT performs the 8*8 2-dimensional inverse discrete cosine transform:
+//
+//	dst[x,y] = (1/8) * Σ_u Σ_v alpha(u) * alpha(v) * src[u,v] *
+//		cos((π/2) * (2*x + 1) * u / 8) *
+//		cos((π/2) * (2*y + 1) * v / 8)
+//
+// x and y are in pixel space, and u and v are in transform space.
+//
+// b acts as both dst and src.
+func slowIDCT(b *block) {
+	var dst [blockSize]float64
+	for y := 0; y < 8; y++ {
+		for x := 0; x < 8; x++ {
+			sum := 0.0
+			for v := 0; v < 8; v++ {
+				for u := 0; u < 8; u++ {
+					sum += alpha(u) * alpha(v) * float64(b[8*v+u]) *
+						cosines[((2*x+1)*u)%32] *
+						cosines[((2*y+1)*v)%32]
+				}
+			}
+			dst[8*y+x] = sum / 8
+		}
+	}
+	// Convert from float64 to int32.
+	for i := range dst {
+		b[i] = int32(dst[i] + 0.5)
+	}
+}
+
+func (b *block) String() string {
+	s := bytes.NewBuffer(nil)
+	fmt.Fprintf(s, "{\n")
+	for y := 0; y < 8; y++ {
+		fmt.Fprintf(s, "\t")
+		for x := 0; x < 8; x++ {
+			fmt.Fprintf(s, "0x%04x, ", uint16(b[8*y+x]))
+		}
+		fmt.Fprintln(s)
+	}
+	fmt.Fprintf(s, "}")
+	return s.String()
+}
+
+// testBlocks are the first 10 pre-IDCT blocks from ../testdata/video-001.jpeg.
+var testBlocks = [10]block{
+	{
+		0x7f, 0xf6, 0x01, 0x07, 0xff, 0x00, 0x00, 0x00,
+		0xf5, 0x01, 0xfa, 0x01, 0xfe, 0x00, 0x01, 0x00,
+		0x05, 0x05, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x01, 0xff, 0xf8, 0x00, 0x01, 0xff, 0x00, 0x00,
+		0x00, 0x01, 0x00, 0x01, 0x00, 0xff, 0xff, 0x00,
+		0xff, 0x0c, 0x00, 0x00, 0x00, 0x00, 0xff, 0x01,
+		0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
+		0x01, 0x00, 0x00, 0x01, 0xff, 0x01, 0x00, 0xfe,
+	},
+	{
+		0x29, 0x07, 0x00, 0xfc, 0x01, 0x01, 0x00, 0x00,
+		0x07, 0x00, 0x03, 0x00, 0x01, 0x00, 0xff, 0xff,
+		0xff, 0xfd, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x04, 0x00, 0xff, 0x01, 0x00, 0x00,
+		0x01, 0x00, 0x01, 0xff, 0x00, 0x00, 0x00, 0x00,
+		0x01, 0xfa, 0x01, 0x00, 0x01, 0x00, 0x01, 0xff,
+		0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0xff, 0x00, 0xff, 0x00, 0x02,
+	},
+	{
+		0xc5, 0xfa, 0x01, 0x00, 0x00, 0x01, 0x00, 0xff,
+		0x02, 0xff, 0x01, 0x00, 0x01, 0x00, 0xff, 0x00,
+		0xff, 0xff, 0x00, 0xff, 0x01, 0x00, 0x00, 0x00,
+		0xff, 0x00, 0x01, 0x00, 0x00, 0x00, 0xff, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff,
+		0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	},
+	{
+		0x86, 0x05, 0x00, 0x02, 0x00, 0x00, 0x01, 0x00,
+		0xf2, 0x06, 0x00, 0x00, 0x01, 0x02, 0x00, 0x00,
+		0xf6, 0xfa, 0xf9, 0x00, 0xff, 0x01, 0x00, 0x00,
+		0xf9, 0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0xff, 0x00, 0xff, 0xff, 0xff, 0x00, 0x00,
+		0xff, 0x00, 0x00, 0x01, 0x00, 0xff, 0x01, 0x00,
+		0x00, 0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x01,
+		0x00, 0x01, 0xff, 0x01, 0x00, 0xff, 0x00, 0x00,
+	},
+	{
+		0x24, 0xfe, 0x00, 0xff, 0x00, 0xff, 0xff, 0x00,
+		0x08, 0xfd, 0x00, 0x01, 0x01, 0x00, 0x01, 0x00,
+		0x06, 0x03, 0x03, 0xff, 0x00, 0x00, 0x00, 0x00,
+		0x04, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff,
+		0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01,
+		0x01, 0x00, 0x01, 0xff, 0x00, 0x01, 0x00, 0x00,
+		0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0xff, 0x01,
+	},
+	{
+		0xcd, 0xff, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01,
+		0x03, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff,
+		0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00,
+		0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x01, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x00,
+		0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0xff,
+	},
+	{
+		0x81, 0xfe, 0x05, 0xff, 0x01, 0xff, 0x01, 0x00,
+		0xef, 0xf9, 0x00, 0xf9, 0x00, 0xff, 0x00, 0xff,
+		0x05, 0xf9, 0x00, 0xf8, 0x01, 0xff, 0x01, 0xff,
+		0x00, 0xff, 0x07, 0x00, 0x01, 0x00, 0x00, 0x00,
+		0x01, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00,
+		0x01, 0x00, 0x00, 0x00, 0xff, 0xff, 0x00, 0x01,
+		0xff, 0x01, 0x01, 0x00, 0xff, 0x00, 0x00, 0x00,
+		0x01, 0x01, 0x00, 0xff, 0x00, 0x00, 0x00, 0xff,
+	},
+	{
+		0x28, 0x00, 0xfe, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x0b, 0x02, 0x01, 0x03, 0x00, 0xff, 0x00, 0x01,
+		0xfe, 0x02, 0x01, 0x03, 0xff, 0x00, 0x00, 0x00,
+		0x01, 0x00, 0xfd, 0x00, 0x01, 0x00, 0xff, 0x00,
+		0x01, 0xff, 0x00, 0xff, 0x01, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0xff, 0x01, 0x01, 0x00, 0xff,
+		0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0xff, 0xff, 0x00, 0x00, 0x00, 0xff, 0x00, 0x01,
+	},
+	{
+		0xdf, 0xf9, 0xfe, 0x00, 0x03, 0x01, 0xff, 0xff,
+		0x04, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
+		0xff, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x01,
+		0x00, 0x00, 0xfe, 0x01, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0xff, 0x01, 0x00, 0x00, 0x00, 0x01,
+		0xff, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00,
+		0x00, 0xff, 0x00, 0xff, 0x01, 0x00, 0x00, 0x01,
+		0xff, 0xff, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00,
+	},
+	{
+		0x88, 0xfd, 0x00, 0x00, 0xff, 0x00, 0x01, 0xff,
+		0xe1, 0x06, 0x06, 0x01, 0xff, 0x00, 0x01, 0x00,
+		0x08, 0x00, 0xfa, 0x00, 0xff, 0xff, 0xff, 0xff,
+		0x08, 0x01, 0x00, 0xff, 0x01, 0xff, 0x00, 0x00,
+		0xf5, 0xff, 0x00, 0x01, 0xff, 0x01, 0x01, 0x00,
+		0xff, 0xff, 0x01, 0xff, 0x01, 0x00, 0x01, 0x00,
+		0x00, 0x01, 0x01, 0xff, 0x00, 0xff, 0x00, 0x01,
+		0x02, 0x00, 0x00, 0xff, 0xff, 0x00, 0xff, 0x00,
+	},
+}