blob: 503b5dc567b27df9d58385464feb726bd2d2bb35 [file] [log] [blame]
// Copyright 2009 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 png
import (
"bufio"
"bytes"
"fmt"
"image"
"image/color"
"io"
"io/ioutil"
"os"
"reflect"
"strings"
"testing"
)
var filenames = []string{
"basn0g01",
"basn0g01-30",
"basn0g02",
"basn0g02-29",
"basn0g04",
"basn0g04-31",
"basn0g08",
"basn0g16",
"basn2c08",
"basn2c16",
"basn3p01",
"basn3p02",
"basn3p04",
"basn3p04-31i",
"basn3p08",
"basn3p08-trns",
"basn4a08",
"basn4a16",
"basn6a08",
"basn6a16",
"ftbbn0g01",
"ftbbn0g02",
"ftbbn0g04",
"ftbbn2c16",
"ftbbn3p08",
"ftbgn2c16",
"ftbgn3p08",
"ftbrn2c08",
"ftbwn0g16",
"ftbwn3p08",
"ftbyn3p08",
"ftp0n0g08",
"ftp0n2c08",
"ftp0n3p08",
"ftp1n3p08",
}
var filenamesPaletted = []string{
"basn3p01",
"basn3p02",
"basn3p04",
"basn3p08",
"basn3p08-trns",
}
var filenamesShort = []string{
"basn0g01",
"basn0g04-31",
"basn6a16",
}
func readPNG(filename string) (image.Image, error) {
f, err := os.Open(filename)
if err != nil {
return nil, err
}
defer f.Close()
return Decode(f)
}
// fakebKGDs maps from filenames to fake bKGD chunks for our approximation to
// the sng command-line tool. Package png doesn't keep that metadata when
// png.Decode returns an image.Image.
var fakebKGDs = map[string]string{
"ftbbn0g01": "bKGD {gray: 0;}\n",
"ftbbn0g02": "bKGD {gray: 0;}\n",
"ftbbn0g04": "bKGD {gray: 0;}\n",
"ftbbn2c16": "bKGD {red: 0; green: 0; blue: 65535;}\n",
"ftbbn3p08": "bKGD {index: 245}\n",
"ftbgn2c16": "bKGD {red: 0; green: 65535; blue: 0;}\n",
"ftbgn3p08": "bKGD {index: 245}\n",
"ftbrn2c08": "bKGD {red: 255; green: 0; blue: 0;}\n",
"ftbwn0g16": "bKGD {gray: 65535;}\n",
"ftbwn3p08": "bKGD {index: 0}\n",
"ftbyn3p08": "bKGD {index: 245}\n",
}
// fakegAMAs maps from filenames to fake gAMA chunks for our approximation to
// the sng command-line tool. Package png doesn't keep that metadata when
// png.Decode returns an image.Image.
var fakegAMAs = map[string]string{
"ftbbn0g01": "",
"ftbbn0g02": "gAMA {0.45455}\n",
}
// fakeIHDRUsings maps from filenames to fake IHDR "using" lines for our
// approximation to the sng command-line tool. The PNG model is that
// transparency (in the tRNS chunk) is separate to the color/grayscale/palette
// color model (in the IHDR chunk). The Go model is that the concrete
// image.Image type returned by png.Decode, such as image.RGBA (with all pixels
// having 100% alpha) or image.NRGBA, encapsulates whether or not the image has
// transparency. This map is a hack to work around the fact that the Go model
// can't otherwise discriminate PNG's "IHDR says color (with no alpha) but tRNS
// says alpha" and "IHDR says color with alpha".
var fakeIHDRUsings = map[string]string{
"ftbbn0g01": " using grayscale;\n",
"ftbbn0g02": " using grayscale;\n",
"ftbbn0g04": " using grayscale;\n",
"ftbbn2c16": " using color;\n",
"ftbgn2c16": " using color;\n",
"ftbrn2c08": " using color;\n",
"ftbwn0g16": " using grayscale;\n",
}
// An approximation of the sng command-line tool.
func sng(w io.WriteCloser, filename string, png image.Image) {
defer w.Close()
bounds := png.Bounds()
cm := png.ColorModel()
var bitdepth int
switch cm {
case color.RGBAModel, color.NRGBAModel, color.AlphaModel, color.GrayModel:
bitdepth = 8
default:
bitdepth = 16
}
cpm, _ := cm.(color.Palette)
var paletted *image.Paletted
if cpm != nil {
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)
}
// Write the filename and IHDR.
io.WriteString(w, "#SNG: from "+filename+".png\nIHDR {\n")
fmt.Fprintf(w, " width: %d; height: %d; bitdepth: %d;\n", bounds.Dx(), bounds.Dy(), bitdepth)
if s, ok := fakeIHDRUsings[filename]; ok {
io.WriteString(w, s)
} else {
switch {
case cm == color.RGBAModel, cm == color.RGBA64Model:
io.WriteString(w, " using color;\n")
case cm == color.NRGBAModel, cm == color.NRGBA64Model:
io.WriteString(w, " using color alpha;\n")
case cm == color.GrayModel, cm == color.Gray16Model:
io.WriteString(w, " using grayscale;\n")
case cpm != nil:
io.WriteString(w, " using color palette;\n")
default:
io.WriteString(w, "unknown PNG decoder color model\n")
}
}
io.WriteString(w, "}\n")
// We fake a gAMA chunk. The test files have a gAMA chunk but the go PNG
// parser ignores it (the PNG spec section 11.3 says "Ancillary chunks may
// be ignored by a decoder").
if s, ok := fakegAMAs[filename]; ok {
io.WriteString(w, s)
} else {
io.WriteString(w, "gAMA {1.0000}\n")
}
// Write the PLTE and tRNS (if applicable).
useTransparent := false
if cpm != nil {
lastAlpha := -1
io.WriteString(w, "PLTE {\n")
for i, c := range cpm {
var r, g, b, a uint8
switch c := c.(type) {
case color.RGBA:
r, g, b, a = c.R, c.G, c.B, 0xff
case color.NRGBA:
r, g, b, a = c.R, c.G, c.B, c.A
default:
panic("unknown palette color type")
}
if a != 0xff {
lastAlpha = i
}
fmt.Fprintf(w, " (%3d,%3d,%3d) # rgb = (0x%02x,0x%02x,0x%02x)\n", r, g, b, r, g, b)
}
io.WriteString(w, "}\n")
if s, ok := fakebKGDs[filename]; ok {
io.WriteString(w, s)
}
if lastAlpha != -1 {
io.WriteString(w, "tRNS {\n")
for i := 0; i <= lastAlpha; i++ {
_, _, _, a := cpm[i].RGBA()
a >>= 8
fmt.Fprintf(w, " %d", a)
}
io.WriteString(w, "}\n")
}
} else if strings.HasPrefix(filename, "ft") {
if s, ok := fakebKGDs[filename]; ok {
io.WriteString(w, s)
}
// We fake a tRNS chunk. The test files' grayscale and truecolor
// transparent images all have their top left corner transparent.
switch c := png.At(0, 0).(type) {
case color.NRGBA:
if c.A == 0 {
useTransparent = true
io.WriteString(w, "tRNS {\n")
switch filename {
case "ftbbn0g01", "ftbbn0g02", "ftbbn0g04":
// The standard image package doesn't have a "gray with
// alpha" type. Instead, we use an image.NRGBA.
fmt.Fprintf(w, " gray: %d;\n", c.R)
default:
fmt.Fprintf(w, " red: %d; green: %d; blue: %d;\n", c.R, c.G, c.B)
}
io.WriteString(w, "}\n")
}
case color.NRGBA64:
if c.A == 0 {
useTransparent = true
io.WriteString(w, "tRNS {\n")
switch filename {
case "ftbwn0g16":
// The standard image package doesn't have a "gray16 with
// alpha" type. Instead, we use an image.NRGBA64.
fmt.Fprintf(w, " gray: %d;\n", c.R)
default:
fmt.Fprintf(w, " red: %d; green: %d; blue: %d;\n", c.R, c.G, c.B)
}
io.WriteString(w, "}\n")
}
}
}
// Write the IMAGE.
io.WriteString(w, "IMAGE {\n pixels hex\n")
for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
switch {
case cm == color.GrayModel:
for x := bounds.Min.X; x < bounds.Max.X; x++ {
gray := png.At(x, y).(color.Gray)
fmt.Fprintf(w, "%02x", gray.Y)
}
case cm == color.Gray16Model:
for x := bounds.Min.X; x < bounds.Max.X; x++ {
gray16 := png.At(x, y).(color.Gray16)
fmt.Fprintf(w, "%04x ", gray16.Y)
}
case cm == color.RGBAModel:
for x := bounds.Min.X; x < bounds.Max.X; x++ {
rgba := png.At(x, y).(color.RGBA)
fmt.Fprintf(w, "%02x%02x%02x ", rgba.R, rgba.G, rgba.B)
}
case cm == color.RGBA64Model:
for x := bounds.Min.X; x < bounds.Max.X; x++ {
rgba64 := png.At(x, y).(color.RGBA64)
fmt.Fprintf(w, "%04x%04x%04x ", rgba64.R, rgba64.G, rgba64.B)
}
case cm == color.NRGBAModel:
for x := bounds.Min.X; x < bounds.Max.X; x++ {
nrgba := png.At(x, y).(color.NRGBA)
switch filename {
case "ftbbn0g01", "ftbbn0g02", "ftbbn0g04":
fmt.Fprintf(w, "%02x", nrgba.R)
default:
if useTransparent {
fmt.Fprintf(w, "%02x%02x%02x ", nrgba.R, nrgba.G, nrgba.B)
} else {
fmt.Fprintf(w, "%02x%02x%02x%02x ", nrgba.R, nrgba.G, nrgba.B, nrgba.A)
}
}
}
case cm == color.NRGBA64Model:
for x := bounds.Min.X; x < bounds.Max.X; x++ {
nrgba64 := png.At(x, y).(color.NRGBA64)
switch filename {
case "ftbwn0g16":
fmt.Fprintf(w, "%04x ", nrgba64.R)
default:
if useTransparent {
fmt.Fprintf(w, "%04x%04x%04x ", nrgba64.R, nrgba64.G, nrgba64.B)
} else {
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++ {
b = b<<uint(bitdepth) | int(paletted.ColorIndexAt(x, y))
c++
if c == 8/bitdepth {
fmt.Fprintf(w, "%02x", b)
b = 0
c = 0
}
}
if c != 0 {
for c != 8/bitdepth {
b = b << uint(bitdepth)
c++
}
fmt.Fprintf(w, "%02x", b)
}
}
io.WriteString(w, "\n")
}
io.WriteString(w, "}\n")
}
func TestReader(t *testing.T) {
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 {
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).(color.NRGBA64)
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.NewScanner(piper)
go sng(pipew, fn, img)
defer piper.Close()
// Read the .sng file.
sf, err := os.Open("testdata/pngsuite/" + fn + ".sng")
if err != nil {
t.Error(fn, err)
continue
}
defer sf.Close()
sb := bufio.NewScanner(sf)
if err != nil {
t.Error(fn, err)
continue
}
// Compare the two, in SNG format, line by line.
for {
pdone := !pb.Scan()
sdone := !sb.Scan()
if pdone && sdone {
break
}
if pdone || sdone {
t.Errorf("%s: Different sizes", fn)
break
}
ps := pb.Text()
ss := sb.Text()
// Newer versions of the sng command line tool append an optional
// color name to the RGB tuple. For example:
// # rgb = (0xff,0xff,0xff) grey100
// # rgb = (0x00,0x00,0xff) blue1
// instead of the older version's plainer:
// # rgb = (0xff,0xff,0xff)
// # rgb = (0x00,0x00,0xff)
// We strip any such name.
if strings.Contains(ss, "# rgb = (") && !strings.HasSuffix(ss, ")") {
if i := strings.LastIndex(ss, ") "); i >= 0 {
ss = ss[:i+1]
}
}
if ps != ss {
t.Errorf("%s: Mismatch\n%s\nversus\n%s\n", fn, ps, ss)
break
}
}
if pb.Err() != nil {
t.Error(fn, pb.Err())
}
if sb.Err() != nil {
t.Error(fn, sb.Err())
}
}
}
var readerErrors = []struct {
file string
err string
}{
{"invalid-zlib.png", "zlib: invalid checksum"},
{"invalid-crc32.png", "invalid checksum"},
{"invalid-noend.png", "unexpected EOF"},
{"invalid-trunc.png", "unexpected EOF"},
}
func TestReaderError(t *testing.T) {
for _, tt := range readerErrors {
img, err := readPNG("testdata/" + tt.file)
if err == nil {
t.Errorf("decoding %s: missing error", tt.file)
continue
}
if !strings.Contains(err.Error(), tt.err) {
t.Errorf("decoding %s: %s, want %s", tt.file, err, tt.err)
}
if img != nil {
t.Errorf("decoding %s: have image + error", tt.file)
}
}
}
func TestPalettedDecodeConfig(t *testing.T) {
for _, fn := range filenamesPaletted {
f, err := os.Open("testdata/pngsuite/" + fn + ".png")
if err != nil {
t.Errorf("%s: open failed: %v", fn, err)
continue
}
defer f.Close()
cfg, err := DecodeConfig(f)
if err != nil {
t.Errorf("%s: %v", fn, err)
continue
}
pal, ok := cfg.ColorModel.(color.Palette)
if !ok {
t.Errorf("%s: expected paletted color model", fn)
continue
}
if pal == nil {
t.Errorf("%s: palette not initialized", fn)
continue
}
}
}
func TestInterlaced(t *testing.T) {
a, err := readPNG("testdata/gray-gradient.png")
if err != nil {
t.Fatal(err)
}
b, err := readPNG("testdata/gray-gradient.interlaced.png")
if err != nil {
t.Fatal(err)
}
if !reflect.DeepEqual(a, b) {
t.Fatalf("decodings differ:\nnon-interlaced:\n%#v\ninterlaced:\n%#v", a, b)
}
}
func TestIncompleteIDATOnRowBoundary(t *testing.T) {
// The following is an invalid 1x2 grayscale PNG image. The header is OK,
// but the zlib-compressed IDAT payload contains two bytes "\x02\x00",
// which is only one row of data (the leading "\x02" is a row filter).
const (
ihdr = "\x00\x00\x00\x0dIHDR\x00\x00\x00\x01\x00\x00\x00\x02\x08\x00\x00\x00\x00\xbc\xea\xe9\xfb"
idat = "\x00\x00\x00\x0eIDAT\x78\x9c\x62\x62\x00\x04\x00\x00\xff\xff\x00\x06\x00\x03\xfa\xd0\x59\xae"
iend = "\x00\x00\x00\x00IEND\xae\x42\x60\x82"
)
_, err := Decode(strings.NewReader(pngHeader + ihdr + idat + iend))
if err == nil {
t.Fatal("got nil error, want non-nil")
}
}
func TestTrailingIDATChunks(t *testing.T) {
// The following is a valid 1x1 PNG image containing color.Gray{255} and
// a trailing zero-length IDAT chunk (see PNG specification section 12.9):
const (
ihdr = "\x00\x00\x00\x0dIHDR\x00\x00\x00\x01\x00\x00\x00\x01\x08\x00\x00\x00\x00\x3a\x7e\x9b\x55"
idatWhite = "\x00\x00\x00\x0eIDAT\x78\x9c\x62\xfa\x0f\x08\x00\x00\xff\xff\x01\x05\x01\x02\x5a\xdd\x39\xcd"
idatZero = "\x00\x00\x00\x00IDAT\x35\xaf\x06\x1e"
iend = "\x00\x00\x00\x00IEND\xae\x42\x60\x82"
)
_, err := Decode(strings.NewReader(pngHeader + ihdr + idatWhite + idatZero + iend))
if err != nil {
t.Fatalf("decoding valid image: %v", err)
}
// Non-zero-length trailing IDAT chunks should be ignored (recoverable error).
// The following chunk contains a single pixel with color.Gray{0}.
const idatBlack = "\x00\x00\x00\x0eIDAT\x78\x9c\x62\x62\x00\x04\x00\x00\xff\xff\x00\x06\x00\x03\xfa\xd0\x59\xae"
img, err := Decode(strings.NewReader(pngHeader + ihdr + idatWhite + idatBlack + iend))
if err != nil {
t.Fatalf("trailing IDAT not ignored: %v", err)
}
if img.At(0, 0) == (color.Gray{0}) {
t.Fatal("decoded image from trailing IDAT chunk")
}
}
func TestMultipletRNSChunks(t *testing.T) {
/*
The following is a valid 1x1 paletted PNG image with a 1-element palette
containing color.NRGBA{0xff, 0x00, 0x00, 0x7f}:
0000000: 8950 4e47 0d0a 1a0a 0000 000d 4948 4452 .PNG........IHDR
0000010: 0000 0001 0000 0001 0803 0000 0028 cb34 .............(.4
0000020: bb00 0000 0350 4c54 45ff 0000 19e2 0937 .....PLTE......7
0000030: 0000 0001 7452 4e53 7f80 5cb4 cb00 0000 ....tRNS..\.....
0000040: 0e49 4441 5478 9c62 6200 0400 00ff ff00 .IDATx.bb.......
0000050: 0600 03fa d059 ae00 0000 0049 454e 44ae .....Y.....IEND.
0000060: 4260 82 B`.
Dropping the tRNS chunk makes that color's alpha 0xff instead of 0x7f.
*/
const (
ihdr = "\x00\x00\x00\x0dIHDR\x00\x00\x00\x01\x00\x00\x00\x01\x08\x03\x00\x00\x00\x28\xcb\x34\xbb"
plte = "\x00\x00\x00\x03PLTE\xff\x00\x00\x19\xe2\x09\x37"
trns = "\x00\x00\x00\x01tRNS\x7f\x80\x5c\xb4\xcb"
idat = "\x00\x00\x00\x0eIDAT\x78\x9c\x62\x62\x00\x04\x00\x00\xff\xff\x00\x06\x00\x03\xfa\xd0\x59\xae"
iend = "\x00\x00\x00\x00IEND\xae\x42\x60\x82"
)
for i := 0; i < 4; i++ {
var b []byte
b = append(b, pngHeader...)
b = append(b, ihdr...)
b = append(b, plte...)
for j := 0; j < i; j++ {
b = append(b, trns...)
}
b = append(b, idat...)
b = append(b, iend...)
var want color.Color
m, err := Decode(bytes.NewReader(b))
switch i {
case 0:
if err != nil {
t.Errorf("%d tRNS chunks: %v", i, err)
continue
}
want = color.RGBA{0xff, 0x00, 0x00, 0xff}
case 1:
if err != nil {
t.Errorf("%d tRNS chunks: %v", i, err)
continue
}
want = color.NRGBA{0xff, 0x00, 0x00, 0x7f}
default:
if err == nil {
t.Errorf("%d tRNS chunks: got nil error, want non-nil", i)
}
continue
}
if got := m.At(0, 0); got != want {
t.Errorf("%d tRNS chunks: got %T %v, want %T %v", i, got, got, want, want)
}
}
}
func TestUnknownChunkLengthUnderflow(t *testing.T) {
data := []byte{0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x06, 0xf4, 0x7c, 0x55, 0x04, 0x1a,
0xd3, 0x11, 0x9a, 0x73, 0x00, 0x00, 0xf8, 0x1e, 0xf3, 0x2e, 0x00, 0x00,
0x01, 0x00, 0xff, 0xff, 0xff, 0xff, 0x07, 0xf4, 0x7c, 0x55, 0x04, 0x1a,
0xd3}
_, err := Decode(bytes.NewReader(data))
if err == nil {
t.Errorf("Didn't fail reading an unknown chunk with length 0xffffffff")
}
}
func benchmarkDecode(b *testing.B, filename string, bytesPerPixel int) {
b.StopTimer()
data, err := ioutil.ReadFile(filename)
if err != nil {
b.Fatal(err)
}
s := string(data)
cfg, err := DecodeConfig(strings.NewReader(s))
if err != nil {
b.Fatal(err)
}
b.SetBytes(int64(cfg.Width * cfg.Height * bytesPerPixel))
b.StartTimer()
for i := 0; i < b.N; i++ {
Decode(strings.NewReader(s))
}
}
func BenchmarkDecodeGray(b *testing.B) {
benchmarkDecode(b, "testdata/benchGray.png", 1)
}
func BenchmarkDecodeNRGBAGradient(b *testing.B) {
benchmarkDecode(b, "testdata/benchNRGBA-gradient.png", 4)
}
func BenchmarkDecodeNRGBAOpaque(b *testing.B) {
benchmarkDecode(b, "testdata/benchNRGBA-opaque.png", 4)
}
func BenchmarkDecodePaletted(b *testing.B) {
benchmarkDecode(b, "testdata/benchPaletted.png", 1)
}
func BenchmarkDecodeRGB(b *testing.B) {
benchmarkDecode(b, "testdata/benchRGB.png", 4)
}
func BenchmarkDecodeInterlacing(b *testing.B) {
benchmarkDecode(b, "testdata/benchRGB-interlace.png", 4)
}
func TestIssue19553(t *testing.T) {
var buf = []byte{
0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x0b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x85, 0x2c, 0x88, 0x80, 0x00, 0x00, 0x00, 0x02, 0x74, 0x52, 0x4e, 0x53, 0x00, 0xff, 0x5b, 0x91, 0x22, 0xb5, 0x00, 0x00, 0x00, 0x02, 0x62, 0x4b, 0x47, 0x44, 0x00, 0xff, 0x87, 0x8f, 0xcc, 0xbf, 0x00, 0x00, 0x00, 0x09, 0x70, 0x48, 0x59, 0x73, 0x00, 0x00, 0x0a, 0xf0, 0x00, 0x00, 0x0a, 0xf0, 0x01, 0x42, 0xac, 0x34, 0x98, 0x00, 0x00, 0x00, 0x07, 0x74, 0x49, 0x4d, 0x45, 0x07, 0xd5, 0x04, 0x02, 0x12, 0x11, 0x11, 0xf7, 0x65, 0x3d, 0x8b, 0x00, 0x00, 0x00, 0x4f, 0x49, 0x44, 0x41, 0x54, 0x08, 0xd7, 0x63, 0xf8, 0xff, 0xff, 0xff, 0xb9, 0xbd, 0x70, 0xf0, 0x8c, 0x01, 0xc8, 0xaf, 0x6e, 0x99, 0x02, 0x05, 0xd9, 0x7b, 0xc1, 0xfc, 0x6b, 0xff, 0xa1, 0xa0, 0x87, 0x30, 0xff, 0xd9, 0xde, 0xbd, 0xd5, 0x4b, 0xf7, 0xee, 0xfd, 0x0e, 0xe3, 0xef, 0xcd, 0x06, 0x19, 0x14, 0xf5, 0x1e, 0xce, 0xef, 0x01, 0x31, 0x92, 0xd7, 0x82, 0x41, 0x31, 0x9c, 0x3f, 0x07, 0x02, 0xee, 0xa1, 0xaa, 0xff, 0xff, 0x9f, 0xe1, 0xd9, 0x56, 0x30, 0xf8, 0x0e, 0xe5, 0x03, 0x00, 0xa9, 0x42, 0x84, 0x3d, 0xdf, 0x8f, 0xa6, 0x8f, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82,
}
_, err := Decode(bytes.NewReader(buf))
if err != chunkOrderError {
t.Errorf("Decode: expected chunkOrderError for transparent gray8, got %v", err)
}
}