image/png: support for more formats

Added support for reading images with grayscale + alpha and
for images with depth 1, 2 or 4.

R=nigeltao
CC=golang-dev
https://golang.org/cl/4174053

src/pkg/image/png/reader.go

@@ -29,11 +29,19 @@ const (
 // A cb is a combination of color type and bit depth.
 const (
 	cbInvalid = iota
+	cbG1
+	cbG2
+	cbG4
 	cbG8
+	cbGA8
 	cbTC8
+	cbP1
+	cbP2
+	cbP4
 	cbP8
 	cbTCA8
 	cbG16
+	cbGA16
 	cbTC16
 	cbTCA16
 )
@@ -70,6 +78,7 @@ type imgOrErr struct {
 
 type decoder struct {
 	width, height int
+	depth         int
 	palette       image.PalettedColorModel
 	cb            int
 	stage         int
@@ -138,7 +147,29 @@ func (d *decoder) parseIHDR(r io.Reader, crc hash.Hash32, length uint32) os.Erro
 		return UnsupportedError("dimension overflow")
 	}
 	d.cb = cbInvalid
-	switch d.tmp[8] {
+	d.depth = int(d.tmp[8])
+	switch d.depth {
+	case 1:
+		switch d.tmp[9] {
+		case ctGrayscale:
+			d.cb = cbG1
+		case ctPaletted:
+			d.cb = cbP1
+		}
+	case 2:
+		switch d.tmp[9] {
+		case ctGrayscale:
+			d.cb = cbG2
+		case ctPaletted:
+			d.cb = cbP2
+		}
+	case 4:
+		switch d.tmp[9] {
+		case ctGrayscale:
+			d.cb = cbG4
+		case ctPaletted:
+			d.cb = cbP4
+		}
 	case 8:
 		switch d.tmp[9] {
 		case ctGrayscale:
@@ -147,6 +178,8 @@ func (d *decoder) parseIHDR(r io.Reader, crc hash.Hash32, length uint32) os.Erro
 			d.cb = cbTC8
 		case ctPaletted:
 			d.cb = cbP8
+		case ctGrayscaleAlpha:
+			d.cb = cbGA8
 		case ctTrueColorAlpha:
 			d.cb = cbTCA8
 		}
@@ -156,6 +189,8 @@ func (d *decoder) parseIHDR(r io.Reader, crc hash.Hash32, length uint32) os.Erro
 			d.cb = cbG16
 		case ctTrueColor:
 			d.cb = cbTC16
+		case ctGrayscaleAlpha:
+			d.cb = cbGA16
 		case ctTrueColorAlpha:
 			d.cb = cbTCA16
 		}
@@ -169,7 +204,7 @@ func (d *decoder) parseIHDR(r io.Reader, crc hash.Hash32, length uint32) os.Erro
 
 func (d *decoder) parsePLTE(r io.Reader, crc hash.Hash32, length uint32) os.Error {
 	np := int(length / 3) // The number of palette entries.
-	if length%3 != 0 || np <= 0 || np > 256 {
+	if length%3 != 0 || np <= 0 || np > 256 || np > 1<<uint(d.depth) {
 		return FormatError("bad PLTE length")
 	}
 	n, err := io.ReadFull(r, d.tmp[0:3*np])
@@ -178,7 +213,7 @@ func (d *decoder) parsePLTE(r io.Reader, crc hash.Hash32, length uint32) os.Erro
 	}
 	crc.Write(d.tmp[0:n])
 	switch d.cb {
-	case cbP8:
+	case cbP1, cbP2, cbP4, cbP8:
 		d.palette = image.PalettedColorModel(make([]image.Color, np))
 		for i := 0; i < np; i++ {
 			d.palette[i] = image.RGBAColor{d.tmp[3*i+0], d.tmp[3*i+1], d.tmp[3*i+2], 0xff}
@@ -206,7 +241,7 @@ func (d *decoder) parsetRNS(r io.Reader, crc hash.Hash32, length uint32) os.Erro
 		return UnsupportedError("grayscale transparency")
 	case cbTC8, cbTC16:
 		return UnsupportedError("truecolor transparency")
-	case cbP8:
+	case cbP1, cbP2, cbP4, cbP8:
 		if n > len(d.palette) {
 			return FormatError("bad tRNS length")
 		}
@@ -214,7 +249,7 @@ func (d *decoder) parsetRNS(r io.Reader, crc hash.Hash32, length uint32) os.Erro
 			rgba := d.palette[i].(image.RGBAColor)
 			d.palette[i] = image.RGBAColor{rgba.R, rgba.G, rgba.B, d.tmp[i]}
 		}
-	case cbTCA8, cbTCA16:
+	case cbGA8, cbGA16, cbTCA8, cbTCA16:
 		return FormatError("tRNS, color type mismatch")
 	}
 	return nil
@@ -240,7 +275,7 @@ func (d *decoder) idatReader(idat io.Reader) (image.Image, os.Error) {
 		return nil, err
 	}
 	defer r.Close()
-	bpp := 0 // Bytes per pixel.
+	bitsPerPixel := 0
 	maxPalette := uint8(0)
 	var (
 		gray     *image.Gray
@@ -253,40 +288,50 @@ func (d *decoder) idatReader(idat io.Reader) (image.Image, os.Error) {
 		img      image.Image
 	)
 	switch d.cb {
-	case cbG8:
-		bpp = 1
+	case cbG1, cbG2, cbG4, cbG8:
+		bitsPerPixel = d.depth
 		gray = image.NewGray(d.width, d.height)
 		img = gray
+	case cbGA8:
+		bitsPerPixel = 16
+		nrgba = image.NewNRGBA(d.width, d.height)
+		img = nrgba
 	case cbTC8:
-		bpp = 3
+		bitsPerPixel = 24
 		rgba = image.NewRGBA(d.width, d.height)
 		img = rgba
-	case cbP8:
-		bpp = 1
+	case cbP1, cbP2, cbP4, cbP8:
+		bitsPerPixel = d.depth
 		paletted = image.NewPaletted(d.width, d.height, d.palette)
 		img = paletted
 		maxPalette = uint8(len(d.palette) - 1)
 	case cbTCA8:
-		bpp = 4
+		bitsPerPixel = 32
 		nrgba = image.NewNRGBA(d.width, d.height)
 		img = nrgba
 	case cbG16:
-		bpp = 2
+		bitsPerPixel = 16
 		gray16 = image.NewGray16(d.width, d.height)
 		img = gray16
+	case cbGA16:
+		bitsPerPixel = 32
+		nrgba64 = image.NewNRGBA64(d.width, d.height)
+		img = nrgba64
 	case cbTC16:
-		bpp = 6
+		bitsPerPixel = 48
 		rgba64 = image.NewRGBA64(d.width, d.height)
 		img = rgba64
 	case cbTCA16:
-		bpp = 8
+		bitsPerPixel = 64
 		nrgba64 = image.NewNRGBA64(d.width, d.height)
 		img = nrgba64
 	}
+	bytesPerPixel := (bitsPerPixel + 7) / 8
+
 	// cr and pr are the bytes for the current and previous row.
 	// The +1 is for the per-row filter type, which is at cr[0].
-	cr := make([]uint8, 1+bpp*d.width)
-	pr := make([]uint8, 1+bpp*d.width)
+	cr := make([]uint8, 1+(bitsPerPixel*d.width+7)/8)
+	pr := make([]uint8, 1+(bitsPerPixel*d.width+7)/8)
 
 	for y := 0; y < d.height; y++ {
 		// Read the decompressed bytes.
@@ -302,26 +347,26 @@ func (d *decoder) idatReader(idat io.Reader) (image.Image, os.Error) {
 		case ftNone:
 			// No-op.
 		case ftSub:
-			for i := bpp; i < len(cdat); i++ {
-				cdat[i] += cdat[i-bpp]
+			for i := bytesPerPixel; i < len(cdat); i++ {
+				cdat[i] += cdat[i-bytesPerPixel]
 			}
 		case ftUp:
 			for i := 0; i < len(cdat); i++ {
 				cdat[i] += pdat[i]
 			}
 		case ftAverage:
-			for i := 0; i < bpp; i++ {
+			for i := 0; i < bytesPerPixel; i++ {
 				cdat[i] += pdat[i] / 2
 			}
-			for i := bpp; i < len(cdat); i++ {
-				cdat[i] += uint8((int(cdat[i-bpp]) + int(pdat[i])) / 2)
+			for i := bytesPerPixel; i < len(cdat); i++ {
+				cdat[i] += uint8((int(cdat[i-bytesPerPixel]) + int(pdat[i])) / 2)
 			}
 		case ftPaeth:
-			for i := 0; i < bpp; i++ {
+			for i := 0; i < bytesPerPixel; i++ {
 				cdat[i] += paeth(0, pdat[i], 0)
 			}
-			for i := bpp; i < len(cdat); i++ {
-				cdat[i] += paeth(cdat[i-bpp], pdat[i], pdat[i-bpp])
+			for i := bytesPerPixel; i < len(cdat); i++ {
+				cdat[i] += paeth(cdat[i-bytesPerPixel], pdat[i], pdat[i-bytesPerPixel])
 			}
 		default:
 			return nil, FormatError("bad filter type")
@@ -329,14 +374,79 @@ func (d *decoder) idatReader(idat io.Reader) (image.Image, os.Error) {
 
 		// Convert from bytes to colors.
 		switch d.cb {
+		case cbG1:
+			for x := 0; x < d.width; x += 8 {
+				b := cdat[x/8]
+				for x2 := 0; x2 < 8 && x+x2 < d.width; x2++ {
+					gray.Set(x+x2, y, image.GrayColor{(b >> 7) * 0xff})
+					b <<= 1
+				}
+			}
+		case cbG2:
+			for x := 0; x < d.width; x += 4 {
+				b := cdat[x/4]
+				for x2 := 0; x2 < 4 && x+x2 < d.width; x2++ {
+					gray.Set(x+x2, y, image.GrayColor{(b >> 6) * 0x55})
+					b <<= 2
+				}
+			}
+		case cbG4:
+			for x := 0; x < d.width; x += 2 {
+				b := cdat[x/2]
+				for x2 := 0; x2 < 2 && x+x2 < d.width; x2++ {
+					gray.Set(x+x2, y, image.GrayColor{(b >> 4) * 0x11})
+					b <<= 4
+				}
+			}
 		case cbG8:
 			for x := 0; x < d.width; x++ {
 				gray.Set(x, y, image.GrayColor{cdat[x]})
 			}
+		case cbGA8:
+			for x := 0; x < d.width; x++ {
+				ycol := cdat[2*x+0]
+				nrgba.Set(x, y, image.NRGBAColor{ycol, ycol, ycol, cdat[2*x+1]})
+			}
 		case cbTC8:
 			for x := 0; x < d.width; x++ {
 				rgba.Set(x, y, image.RGBAColor{cdat[3*x+0], cdat[3*x+1], cdat[3*x+2], 0xff})
 			}
+		case cbP1:
+			for x := 0; x < d.width; x += 8 {
+				b := cdat[x/8]
+				for x2 := 0; x2 < 8 && x+x2 < d.width; x2++ {
+					idx := b >> 7
+					if idx > maxPalette {
+						return nil, FormatError("palette index out of range")
+					}
+					paletted.SetColorIndex(x+x2, y, idx)
+					b <<= 1
+				}
+			}
+		case cbP2:
+			for x := 0; x < d.width; x += 4 {
+				b := cdat[x/4]
+				for x2 := 0; x2 < 4 && x+x2 < d.width; x2++ {
+					idx := b >> 6
+					if idx > maxPalette {
+						return nil, FormatError("palette index out of range")
+					}
+					paletted.SetColorIndex(x+x2, y, idx)
+					b <<= 2
+				}
+			}
+		case cbP4:
+			for x := 0; x < d.width; x += 2 {
+				b := cdat[x/2]
+				for x2 := 0; x2 < 2 && x+x2 < d.width; x2++ {
+					idx := b >> 4
+					if idx > maxPalette {
+						return nil, FormatError("palette index out of range")
+					}
+					paletted.SetColorIndex(x+x2, y, idx)
+					b <<= 4
+				}
+			}
 		case cbP8:
 			for x := 0; x < d.width; x++ {
 				if cdat[x] > maxPalette {
@@ -353,6 +463,12 @@ func (d *decoder) idatReader(idat io.Reader) (image.Image, os.Error) {
 				ycol := uint16(cdat[2*x+0])<<8 | uint16(cdat[2*x+1])
 				gray16.Set(x, y, image.Gray16Color{ycol})
 			}
+		case cbGA16:
+			for x := 0; x < d.width; x++ {
+				ycol := uint16(cdat[4*x+0])<<8 | uint16(cdat[4*x+1])
+				acol := uint16(cdat[4*x+2])<<8 | uint16(cdat[4*x+3])
+				nrgba64.Set(x, y, image.NRGBA64Color{ycol, ycol, ycol, acol})
+			}
 		case cbTC16:
 			for x := 0; x < d.width; x++ {
 				rcol := uint16(cdat[6*x+0])<<8 | uint16(cdat[6*x+1])
@@ -565,16 +681,20 @@ func DecodeConfig(r io.Reader) (image.Config, os.Error) {
 	}
 	var cm image.ColorModel
 	switch d.cb {
-	case cbG8:
+	case cbG1, cbG2, cbG4, cbG8:
 		cm = image.GrayColorModel
+	case cbGA8:
+		cm = image.NRGBAColorModel
 	case cbTC8:
 		cm = image.RGBAColorModel
-	case cbP8:
+	case cbP1, cbP2, cbP4, cbP8:
 		cm = d.palette
 	case cbTCA8:
 		cm = image.NRGBAColorModel
 	case cbG16:
 		cm = image.Gray16ColorModel
+	case cbGA16:
+		cm = image.NRGBA64ColorModel
 	case cbTC16:
 		cm = image.RGBA64ColorModel
 	case cbTCA16:

src/pkg/image/png/reader_test.go

@@ -13,23 +13,23 @@ import (
 	"testing"
 )
 
-// The go PNG library currently supports only a subset of the full PNG specification.
-// In particular, bit depths other than 8 or 16 are not supported, nor are grayscale-
-// alpha images.
 var filenames = []string{
-	//"basn0g01",	// bit depth is not 8 or 16
-	//"basn0g02",	// bit depth is not 8 or 16
-	//"basn0g04",	// bit depth is not 8 or 16
+	"basn0g01",
+	"basn0g01-30",
+	"basn0g02",
+	"basn0g02-29",
+	"basn0g04",
+	"basn0g04-31",
 	"basn0g08",
 	"basn0g16",
 	"basn2c08",
 	"basn2c16",
-	//"basn3p01",	// bit depth is not 8 or 16
-	//"basn3p02",	// bit depth is not 8 or 16
-	//"basn3p04",	// bit depth is not 8 or 16
+	"basn3p01",
+	"basn3p02",
+	"basn3p04",
 	"basn3p08",
-	//"basn4a08",	// grayscale-alpha color model
-	//"basn4a16",	// grayscale-alpha color model
+	"basn4a08",
+	"basn4a16",
 	"basn6a08",
 	"basn6a16",
 }
@@ -58,7 +58,16 @@ func sng(w io.WriteCloser, filename string, png image.Image) {
 	cpm, _ := cm.(image.PalettedColorModel)
 	var paletted *image.Paletted
 	if cpm != nil {
-		bitdepth = 8
+		switch {
+		case len(cpm) <= 2:
+			bitdepth = 1
+		case len(cpm) <= 4:
+			bitdepth = 2
+		case len(cpm) <= 16:
+			bitdepth = 4
+		default:
+			bitdepth = 8
+		}
 		paletted = png.(*image.Paletted)
 	}
 
@@ -131,8 +140,15 @@ func sng(w io.WriteCloser, filename string, png image.Image) {
 				fmt.Fprintf(w, "%04x%04x%04x%04x ", nrgba64.R, nrgba64.G, nrgba64.B, nrgba64.A)
 			}
 		case cpm != nil:
+			var b, c int
 			for x := bounds.Min.X; x < bounds.Max.X; x++ {
-				fmt.Fprintf(w, "%02x", paletted.ColorIndexAt(x, y))
+				b = b<<uint(bitdepth) | int(paletted.ColorIndexAt(x, y))
+				c++
+				if c == 8/bitdepth {
+					fmt.Fprintf(w, "%02x", b)
+					b = 0
+					c = 0
+				}
 			}
 		}
 		io.WriteString(w, "\n")
@@ -143,14 +159,25 @@ func sng(w io.WriteCloser, filename string, png image.Image) {
 func TestReader(t *testing.T) {
 	for _, fn := range filenames {
 		// Read the .png file.
-		image, err := readPng("testdata/pngsuite/" + fn + ".png")
+		img, err := readPng("testdata/pngsuite/" + fn + ".png")
 		if err != nil {
 			t.Error(fn, err)
 			continue
 		}
+
+		if fn == "basn4a16" {
+			// basn4a16.sng is gray + alpha but sng() will produce true color + alpha
+			// so we just check a single random pixel.
+			c := img.At(2, 1).(image.NRGBA64Color)
+			if c.R != 0x11a7 || c.G != 0x11a7 || c.B != 0x11a7 || c.A != 0x1085 {
+				t.Error(fn, fmt.Errorf("wrong pixel value at (2, 1): %x", c))
+			}
+			continue
+		}
+
 		piper, pipew := io.Pipe()
 		pb := bufio.NewReader(piper)
-		go sng(pipew, fn, image)
+		go sng(pipew, fn, img)
 		defer piper.Close()
 
 		// Read the .sng file.

src/pkg/image/png/testdata/pngsuite/README

@@ -5,5 +5,14 @@ README.original gives the following license for those files:
 	Permission to use, copy, and distribute these images for any purpose
 	and without fee is hereby granted.
 
+
+The files basn0g01-30.png, basn0g02-29.png and basn0g04-31.png are in fact
+not part of pngsuite but were created from files in pngsuite. Their non-power-
+of-two sizes makes them useful for testing bit-depths smaller than a byte.
+
 The *.sng files in this directory were generated from the *.png files
-by the sng command-line tool.
+by the sng command-line tool and some hand editing. The files
+basn0g0{1,2,4}.sng were actually generated by first converting the PNG
+to a bitdepth of 8 and then running sng on them. basn4a08.sng was generated
+by from a 16-bit rgba version of basn4a08.png rather than the original
+gray + alpha.

src/pkg/image/png/testdata/pngsuite/basn0g01-30.sng

+#SNG: from basn0g01-30.png
+IHDR {
+    width: 30; height: 30; bitdepth: 8;
+    using grayscale;
+}
+gAMA {1.0000}
+IMAGE {
+    pixels hex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}

src/pkg/image/png/testdata/pngsuite/basn0g01.sng

 #SNG: from basn0g01.png
 IHDR {
-    width: 32; height: 32; bitdepth: 1;
+    width: 32; height: 32; bitdepth: 8;
     using grayscale;
 }
 gAMA {1.0000}
 IMAGE {
     pixels hex
-fffffffe
-fffffffc
-fffffff8
-fffffff0
-f3f3ffe0
-f3f3ffc0
-f3f3ff80
-f333ff00
-f333fe00
-f333fc00
-f807f800
-f807f000
-fccfe000
-fccfc000
-ffff8000
-ffff0000
-fffe0000
-fffc0000
-fff80fe0
-fff00fe0
-ffe00c30
-ffc00c30
-ff800fe0
-ff000fe0
-fe000c30
-fc000c30
-f8000fe0
-f0000fe0
-e0000000
-c0000000
-80000000
-00000000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 }

src/pkg/image/png/testdata/pngsuite/basn0g02-29.sng

+#SNG: from basn0g02-29.png
+IHDR {
+    width: 29; height: 29; bitdepth: 8;
+    using grayscale;
+}
+gAMA {1.0000}
+IMAGE {
+    pixels hex
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaff
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aa
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaff
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aa
+}

src/pkg/image/png/testdata/pngsuite/basn0g02.sng

 #SNG: from basn0g02.png
 IHDR {
-    width: 32; height: 32; bitdepth: 2;
+    width: 32; height: 32; bitdepth: 8;
     using grayscale;
 }
 gAMA {1.0000}
 IMAGE {
     pixels hex
-0055aaff0055aaff
-0055aaff0055aaff
-0055aaff0055aaff
-0055aaff0055aaff
-55aaff0055aaff00
-55aaff0055aaff00
-55aaff0055aaff00
-55aaff0055aaff00
-aaff0055aaff0055
-aaff0055aaff0055
-aaff0055aaff0055
-aaff0055aaff0055
-ff0055aaff0055aa
-ff0055aaff0055aa
-ff0055aaff0055aa
-ff0055aaff0055aa
-0055aaff0055aaff
-0055aaff0055aaff
-0055aaff0055aaff
-0055aaff0055aaff
-55aaff0055aaff00
-55aaff0055aaff00
-55aaff0055aaff00
-55aaff0055aaff00
-aaff0055aaff0055
-aaff0055aaff0055
-aaff0055aaff0055
-aaff0055aaff0055
-ff0055aaff0055aa
-ff0055aaff0055aa
-ff0055aaff0055aa
-ff0055aaff0055aa
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00000000
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00000000
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00000000
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00000000
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055555555
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055555555
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055555555
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055555555
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaa
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff
+0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00000000
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00000000
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00000000
+55555555aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff00000000
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055555555
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055555555
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055555555
+aaaaaaaaffffffff0000000055555555aaaaaaaaffffffff0000000055555555
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaa
+ffffffff0000000055555555aaaaaaaaffffffff0000000055555555aaaaaaaa
 }

src/pkg/image/png/testdata/pngsuite/basn0g04-31.sng

+#SNG: from basn0g04-31.png
+IHDR {
+    width: 31; height: 31; bitdepth: 8;
+    using grayscale;
+}
+gAMA {1.0000}
+IMAGE {
+    pixels hex
+00000000111111112222222233333333444444445555555566666666777777
+00000000111111112222222233333333444444445555555566666666777777
+00000000111111112222222233333333444444445555555566666666777777
+00000000111111112222222233333333444444445555555566666666777777
+11111111222222223333333344444444555555556666666677777777888888
+11111111222222223333333344444444555555556666666677777777888888
+11111111222222223333333344444444555555556666666677777777888888
+11111111222222223333333344444444555555556666666677777777888888
+22222222333333334444444455555555666666667777777788888888999999
+22222222333333334444444455555555666666667777777788888888999999
+22222222333333334444444455555555666666667777777788888888999999
+22222222333333334444444455555555666666667777777788888888999999
+33333333444444445555555566666666777777778888888899999999aaaaaa
+33333333444444445555555566666666777777778888888899999999aaaaaa
+33333333444444445555555566666666777777778888888899999999aaaaaa
+33333333444444445555555566666666777777778888888899999999aaaaaa
+444444445555555566666666777777778888888899999999aaaaaaaabbbbbb
+444444445555555566666666777777778888888899999999aaaaaaaabbbbbb
+444444445555555566666666777777778888888899999999aaaaaaaabbbbbb
+444444445555555566666666777777778888888899999999aaaaaaaabbbbbb
+5555555566666666777777778888888899999999aaaaaaaabbbbbbbbcccccc
+5555555566666666777777778888888899999999aaaaaaaabbbbbbbbcccccc
+5555555566666666777777778888888899999999aaaaaaaabbbbbbbbcccccc
+5555555566666666777777778888888899999999aaaaaaaabbbbbbbbcccccc
+66666666777777778888888899999999aaaaaaaabbbbbbbbccccccccdddddd
+66666666777777778888888899999999aaaaaaaabbbbbbbbccccccccdddddd
+66666666777777778888888899999999aaaaaaaabbbbbbbbccccccccdddddd
+66666666777777778888888899999999aaaaaaaabbbbbbbbccccccccdddddd
+777777778888888899999999aaaaaaaabbbbbbbbccccccccddddddddeeeeee
+777777778888888899999999aaaaaaaabbbbbbbbccccccccddddddddeeeeee
+777777778888888899999999aaaaaaaabbbbbbbbccccccccddddddddeeeeee
+}

src/pkg/image/png/testdata/pngsuite/basn0g04.sng

 #SNG: from basn0g04.png
 IHDR {
-    width: 32; height: 32; bitdepth: 4;
+    width: 32; height: 32; bitdepth: 8;
     using grayscale;
 }
 gAMA {1.0000}
 IMAGE {
     pixels hex
-00001111222233334444555566667777
-00001111222233334444555566667777
-00001111222233334444555566667777
-00001111222233334444555566667777
-11112222333344445555666677778888
-11112222333344445555666677778888
-11112222333344445555666677778888
-11112222333344445555666677778888
-22223333444455556666777788889999
-22223333444455556666777788889999
-22223333444455556666777788889999
-22223333444455556666777788889999
-3333444455556666777788889999aaaa
-3333444455556666777788889999aaaa
-3333444455556666777788889999aaaa
-3333444455556666777788889999aaaa
-444455556666777788889999aaaabbbb
-444455556666777788889999aaaabbbb
-444455556666777788889999aaaabbbb
-444455556666777788889999aaaabbbb
-55556666777788889999aaaabbbbcccc
-55556666777788889999aaaabbbbcccc
-55556666777788889999aaaabbbbcccc
-55556666777788889999aaaabbbbcccc
-6666777788889999aaaabbbbccccdddd
-6666777788889999aaaabbbbccccdddd
-6666777788889999aaaabbbbccccdddd
-6666777788889999aaaabbbbccccdddd
-777788889999aaaabbbbccccddddeeee
-777788889999aaaabbbbccccddddeeee
-777788889999aaaabbbbccccddddeeee
-777788889999aaaabbbbccccddddeeee
+0000000011111111222222223333333344444444555555556666666677777777
+0000000011111111222222223333333344444444555555556666666677777777
+0000000011111111222222223333333344444444555555556666666677777777
+0000000011111111222222223333333344444444555555556666666677777777
+1111111122222222333333334444444455555555666666667777777788888888
+1111111122222222333333334444444455555555666666667777777788888888
+1111111122222222333333334444444455555555666666667777777788888888
+1111111122222222333333334444444455555555666666667777777788888888
+2222222233333333444444445555555566666666777777778888888899999999
+2222222233333333444444445555555566666666777777778888888899999999
+2222222233333333444444445555555566666666777777778888888899999999
+2222222233333333444444445555555566666666777777778888888899999999
+33333333444444445555555566666666777777778888888899999999aaaaaaaa
+33333333444444445555555566666666777777778888888899999999aaaaaaaa
+33333333444444445555555566666666777777778888888899999999aaaaaaaa
+33333333444444445555555566666666777777778888888899999999aaaaaaaa
+444444445555555566666666777777778888888899999999aaaaaaaabbbbbbbb
+444444445555555566666666777777778888888899999999aaaaaaaabbbbbbbb
+444444445555555566666666777777778888888899999999aaaaaaaabbbbbbbb
+444444445555555566666666777777778888888899999999aaaaaaaabbbbbbbb
+5555555566666666777777778888888899999999aaaaaaaabbbbbbbbcccccccc
+5555555566666666777777778888888899999999aaaaaaaabbbbbbbbcccccccc
+5555555566666666777777778888888899999999aaaaaaaabbbbbbbbcccccccc
+5555555566666666777777778888888899999999aaaaaaaabbbbbbbbcccccccc
+66666666777777778888888899999999aaaaaaaabbbbbbbbccccccccdddddddd
+66666666777777778888888899999999aaaaaaaabbbbbbbbccccccccdddddddd
+66666666777777778888888899999999aaaaaaaabbbbbbbbccccccccdddddddd
+66666666777777778888888899999999aaaaaaaabbbbbbbbccccccccdddddddd
+777777778888888899999999aaaaaaaabbbbbbbbccccccccddddddddeeeeeeee
+777777778888888899999999aaaaaaaabbbbbbbbccccccccddddddddeeeeeeee
+777777778888888899999999aaaaaaaabbbbbbbbccccccccddddddddeeeeeeee
+777777778888888899999999aaaaaaaabbbbbbbbccccccccddddddddeeeeeeee
 }

src/pkg/image/png/testdata/pngsuite/basn3p02.sng

@@ -4,14 +4,11 @@ IHDR {
     using color palette;
 }
 gAMA {1.0000}
-sBIT {
-    red: 1; green: 1; blue: 1;
-}
 PLTE {
-    (  0,255,  0)     # rgb = (0x00,0xff,0x00) green1
-    (255,  0,  0)     # rgb = (0xff,0x00,0x00) red1
-    (255,255,  0)     # rgb = (0xff,0xff,0x00) yellow1
-    (  0,  0,255)     # rgb = (0x00,0x00,0xff) blue1
+    (  0,255,  0)     # rgb = (0x00,0xff,0x00)
+    (255,  0,  0)     # rgb = (0xff,0x00,0x00)
+    (255,255,  0)     # rgb = (0xff,0xff,0x00)
+    (  0,  0,255)     # rgb = (0x00,0x00,0xff)
 }
 IMAGE {
     pixels hex

src/pkg/image/png/testdata/pngsuite/basn3p04.sng

@@ -4,19 +4,16 @@ IHDR {
     using color palette;
 }
 gAMA {1.0000}
-sBIT {
-    red: 4; green: 4; blue: 4;
-}
 PLTE {
     ( 34,  0,255)     # rgb = (0x22,0x00,0xff)
-    (  0,255,255)     # rgb = (0x00,0xff,0xff) cyan1
+    (  0,255,255)     # rgb = (0x00,0xff,0xff)
     (136,  0,255)     # rgb = (0x88,0x00,0xff)
     ( 34,255,  0)     # rgb = (0x22,0xff,0x00)
     (  0,153,255)     # rgb = (0x00,0x99,0xff)
     (255,102,  0)     # rgb = (0xff,0x66,0x00)
     (221,  0,255)     # rgb = (0xdd,0x00,0xff)
     (119,255,  0)     # rgb = (0x77,0xff,0x00)
-    (255,  0,  0)     # rgb = (0xff,0x00,0x00) red1
+    (255,  0,  0)     # rgb = (0xff,0x00,0x00)
     (  0,255,153)     # rgb = (0x00,0xff,0x99)
     (221,255,  0)     # rgb = (0xdd,0xff,0x00)
     (255,  0,187)     # rgb = (0xff,0x00,0xbb)