Imported Upstream version 2011.04.13upstream/2011.04.13

7 files changed, 255 insertions, 9 deletions

diff --git a/src/pkg/image/decode_test.go b/src/pkg/image/decode_test.go
index 5b87344c5..0716ad905 100644
--- a/src/pkg/image/decode_test.go
+++ b/src/pkg/image/decode_test.go
@@ -34,7 +34,7 @@ var imageTests = []imageTest{
 }
 
 func decode(filename string) (image.Image, string, os.Error) {
-	f, err := os.Open(filename, os.O_RDONLY, 0400)
+	f, err := os.Open(filename)
 	if err != nil {
 		return nil, "", err
 	}
diff --git a/src/pkg/image/format.go b/src/pkg/image/format.go
index 1d541b094..b4859325e 100644
--- a/src/pkg/image/format.go
+++ b/src/pkg/image/format.go
@@ -25,7 +25,8 @@ var formats []format
 
 // RegisterFormat registers an image format for use by Decode.
 // Name is the name of the format, like "jpeg" or "png".
-// Magic is the magic prefix that identifies the format's encoding.
+// Magic is the magic prefix that identifies the format's encoding. The magic
+// string can contain "?" wildcards that each match any one byte.
 // Decode is the function that decodes the encoded image.
 // DecodeConfig is the function that decodes just its configuration.
 func RegisterFormat(name, magic string, decode func(io.Reader) (Image, os.Error), decodeConfig func(io.Reader) (Config, os.Error)) {
@@ -46,11 +47,24 @@ func asReader(r io.Reader) reader {
 	return bufio.NewReader(r)
 }
 
-// sniff determines the format of r's data.
+// Match returns whether magic matches b. Magic may contain "?" wildcards.
+func match(magic string, b []byte) bool {
+	if len(magic) != len(b) {
+		return false
+	}
+	for i, c := range b {
+		if magic[i] != c && magic[i] != '?' {
+			return false
+		}
+	}
+	return true
+}
+
+// Sniff determines the format of r's data.
 func sniff(r reader) format {
 	for _, f := range formats {
-		s, err := r.Peek(len(f.magic))
-		if err == nil && string(s) == f.magic {
+		b, err := r.Peek(len(f.magic))
+		if err == nil && match(f.magic, b) {
 			return f
 		}
 	}
diff --git a/src/pkg/image/png/reader_test.go b/src/pkg/image/png/reader_test.go
index 8314a8338..efa6336d7 100644
--- a/src/pkg/image/png/reader_test.go
+++ b/src/pkg/image/png/reader_test.go
@@ -34,8 +34,14 @@ var filenames = []string{
 	"basn6a16",
 }
 
+var filenamesShort = []string{
+	"basn0g01",
+	"basn0g04-31",
+	"basn6a16",
+}
+
 func readPng(filename string) (image.Image, os.Error) {
-	f, err := os.Open(filename, os.O_RDONLY, 0444)
+	f, err := os.Open(filename)
 	if err != nil {
 		return nil, err
 	}
@@ -157,7 +163,11 @@ func sng(w io.WriteCloser, filename string, png image.Image) {
 }
 
 func TestReader(t *testing.T) {
-	for _, fn := range filenames {
+	names := filenames
+	if testing.Short() {
+		names = filenamesShort
+	}
+	for _, fn := range names {
 		// Read the .png file.
 		img, err := readPng("testdata/pngsuite/" + fn + ".png")
 		if err != nil {
@@ -181,7 +191,7 @@ func TestReader(t *testing.T) {
 		defer piper.Close()
 
 		// Read the .sng file.
-		sf, err := os.Open("testdata/pngsuite/"+fn+".sng", os.O_RDONLY, 0444)
+		sf, err := os.Open("testdata/pngsuite/" + fn + ".sng")
 		if err != nil {
 			t.Error(fn, err)
 			continue
diff --git a/src/pkg/image/png/writer_test.go b/src/pkg/image/png/writer_test.go
index f218a5564..4d9929f31 100644
--- a/src/pkg/image/png/writer_test.go
+++ b/src/pkg/image/png/writer_test.go
@@ -32,7 +32,11 @@ func diff(m0, m1 image.Image) os.Error {
 
 func TestWriter(t *testing.T) {
 	// The filenames variable is declared in reader_test.go.
-	for _, fn := range filenames {
+	names := filenames
+	if testing.Short() {
+		names = filenamesShort
+	}
+	for _, fn := range names {
 		qfn := "testdata/pngsuite/" + fn + ".png"
 		// Read the image.
 		m0, err := readPng(qfn)
diff --git a/src/pkg/image/ycbcr/Makefile b/src/pkg/image/ycbcr/Makefile
new file mode 100644
index 000000000..a9c4c1367
--- /dev/null
+++ b/src/pkg/image/ycbcr/Makefile
@@ -0,0 +1,11 @@
+# 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.
+
+include ../../../Make.inc
+
+TARG=image/ycbcr
+GOFILES=\
+	ycbcr.go\
+
+include ../../../Make.pkg
diff --git a/src/pkg/image/ycbcr/ycbcr.go b/src/pkg/image/ycbcr/ycbcr.go
new file mode 100644
index 000000000..b2e033b82
--- /dev/null
+++ b/src/pkg/image/ycbcr/ycbcr.go
@@ -0,0 +1,174 @@
+// 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.
+
+// The ycbcr package provides images from the Y'CbCr color model.
+//
+// JPEG, VP8, the MPEG family and other codecs use this color model. Such
+// codecs often use the terms YUV and Y'CbCr interchangeably, but strictly
+// speaking, the term YUV applies only to analog video signals.
+//
+// Conversion between RGB and Y'CbCr is lossy and there are multiple, slightly
+// different formulae for converting between the two. This package follows
+// the JFIF specification at http://www.w3.org/Graphics/JPEG/jfif3.pdf.
+package ycbcr
+
+import (
+	"image"
+)
+
+// RGBToYCbCr converts an RGB triple to a YCbCr triple. All components lie
+// within the range [0, 255].
+func RGBToYCbCr(r, g, b uint8) (uint8, uint8, uint8) {
+	// The JFIF specification says:
+	//	Y' =  0.2990*R + 0.5870*G + 0.1140*B
+	//	Cb = -0.1687*R - 0.3313*G + 0.5000*B + 128
+	//	Cr =  0.5000*R - 0.4187*G - 0.0813*B + 128
+	// http://www.w3.org/Graphics/JPEG/jfif3.pdf says Y but means Y'.
+	r1 := int(r)
+	g1 := int(g)
+	b1 := int(b)
+	yy := (19595*r1 + 38470*g1 + 7471*b1 + 1<<15) >> 16
+	cb := (-11056*r1 - 21712*g1 + 32768*b1 + 257<<15) >> 16
+	cr := (32768*r1 - 27440*g1 - 5328*b1 + 257<<15) >> 16
+	if yy < 0 {
+		yy = 0
+	} else if yy > 255 {
+		yy = 255
+	}
+	if cb < 0 {
+		cb = 0
+	} else if cb > 255 {
+		cb = 255
+	}
+	if cr < 0 {
+		cr = 0
+	} else if cr > 255 {
+		cr = 255
+	}
+	return uint8(yy), uint8(cb), uint8(cr)
+}
+
+// YCbCrToRGB converts a YCbCr triple to an RGB triple. All components lie
+// within the range [0, 255].
+func YCbCrToRGB(y, cb, cr uint8) (uint8, uint8, uint8) {
+	// The JFIF specification says:
+	//	R = Y' + 1.40200*(Cr-128)
+	//	G = Y' - 0.34414*(Cb-128) - 0.71414*(Cr-128)
+	//	B = Y' + 1.77200*(Cb-128)
+	// http://www.w3.org/Graphics/JPEG/jfif3.pdf says Y but means Y'.
+	yy1 := int(y)<<16 + 1<<15
+	cb1 := int(cb) - 128
+	cr1 := int(cr) - 128
+	r := (yy1 + 91881*cr1) >> 16
+	g := (yy1 - 22554*cb1 - 46802*cr1) >> 16
+	b := (yy1 + 116130*cb1) >> 16
+	if r < 0 {
+		r = 0
+	} else if r > 255 {
+		r = 255
+	}
+	if g < 0 {
+		g = 0
+	} else if g > 255 {
+		g = 255
+	}
+	if b < 0 {
+		b = 0
+	} else if b > 255 {
+		b = 255
+	}
+	return uint8(r), uint8(g), uint8(b)
+}
+
+// YCbCrColor represents a fully opaque 24-bit Y'CbCr color, having 8 bits for
+// each of one luma and two chroma components.
+type YCbCrColor struct {
+	Y, Cb, Cr uint8
+}
+
+func (c YCbCrColor) RGBA() (uint32, uint32, uint32, uint32) {
+	r, g, b := YCbCrToRGB(c.Y, c.Cb, c.Cr)
+	return uint32(r) * 0x101, uint32(g) * 0x101, uint32(b) * 0x101, 0xffff
+}
+
+func toYCbCrColor(c image.Color) image.Color {
+	if _, ok := c.(YCbCrColor); ok {
+		return c
+	}
+	r, g, b, _ := c.RGBA()
+	y, u, v := RGBToYCbCr(uint8(r>>8), uint8(g>>8), uint8(b>>8))
+	return YCbCrColor{y, u, v}
+}
+
+// YCbCrColorModel is the color model for YCbCrColor.
+var YCbCrColorModel image.ColorModel = image.ColorModelFunc(toYCbCrColor)
+
+// SubsampleRatio is the chroma subsample ratio used in a YCbCr image.
+type SubsampleRatio int
+
+const (
+	SubsampleRatio444 SubsampleRatio = iota
+	SubsampleRatio422
+	SubsampleRatio420
+)
+
+// YCbCr is an in-memory image of YCbCr colors. There is one Y sample per pixel,
+// but each Cb and Cr sample can span one or more pixels.
+// YStride is the Y slice index delta between vertically adjacent pixels.
+// CStride is the Cb and Cr slice index delta between vertically adjacent pixels
+// that map to separate chroma samples.
+// It is not an absolute requirement, but YStride and len(Y) are typically
+// multiples of 8, and:
+//	For 4:4:4, CStride == YStride/1 && len(Cb) == len(Cr) == len(Y)/1.
+//	For 4:2:2, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/2.
+//	For 4:2:0, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/4.
+type YCbCr struct {
+	Y              []uint8
+	Cb             []uint8
+	Cr             []uint8
+	YStride        int
+	CStride        int
+	SubsampleRatio SubsampleRatio
+	Rect           image.Rectangle
+}
+
+func (p *YCbCr) ColorModel() image.ColorModel {
+	return YCbCrColorModel
+}
+
+func (p *YCbCr) Bounds() image.Rectangle {
+	return p.Rect
+}
+
+func (p *YCbCr) At(x, y int) image.Color {
+	if !p.Rect.Contains(image.Point{x, y}) {
+		return YCbCrColor{}
+	}
+	switch p.SubsampleRatio {
+	case SubsampleRatio422:
+		i := x / 2
+		return YCbCrColor{
+			p.Y[y*p.YStride+x],
+			p.Cb[y*p.CStride+i],
+			p.Cr[y*p.CStride+i],
+		}
+	case SubsampleRatio420:
+		i, j := x/2, y/2
+		return YCbCrColor{
+			p.Y[y*p.YStride+x],
+			p.Cb[j*p.CStride+i],
+			p.Cr[j*p.CStride+i],
+		}
+	}
+	// Default to 4:4:4 subsampling.
+	return YCbCrColor{
+		p.Y[y*p.YStride+x],
+		p.Cb[y*p.CStride+x],
+		p.Cr[y*p.CStride+x],
+	}
+}
+
+func (p *YCbCr) Opaque() bool {
+	return true
+}
diff --git a/src/pkg/image/ycbcr/ycbcr_test.go b/src/pkg/image/ycbcr/ycbcr_test.go
new file mode 100644
index 000000000..2e60a6f61
--- /dev/null
+++ b/src/pkg/image/ycbcr/ycbcr_test.go
@@ -0,0 +1,33 @@
+// 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 ycbcr
+
+import (
+	"testing"
+)
+
+func delta(x, y uint8) uint8 {
+	if x >= y {
+		return x - y
+	}
+	return y - x
+}
+
+// Test that a subset of RGB space can be converted to YCbCr and back to within
+// 1/256 tolerance.
+func TestRoundtrip(t *testing.T) {
+	for r := 0; r < 255; r += 7 {
+		for g := 0; g < 255; g += 5 {
+			for b := 0; b < 255; b += 3 {
+				r0, g0, b0 := uint8(r), uint8(g), uint8(b)
+				y, cb, cr := RGBToYCbCr(r0, g0, b0)
+				r1, g1, b1 := YCbCrToRGB(y, cb, cr)
+				if delta(r0, r1) > 1 || delta(g0, g1) > 1 || delta(b0, b1) > 1 {
+					t.Fatalf("r0, g0, b0 = %d, %d, %d   r1, g1, b1 = %d, %d, %d", r0, g0, b0, r1, g1, b1)
+				}
+			}
+		}
+	}
+}