Merge pull request #7 from gnoack/picons2

.github/workflows/test.yml

@@ -10,13 +10,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        go-version: [1.14, 1.18]
+        go-version: [1.19, 1.21]
 
     steps:
     - uses: actions/checkout@v2
       with:
         persist-credentials: false
-    - uses: WillAbides/setup-go-faster@v1.7.0
+    - uses: WillAbides/setup-go-faster@v1.9.1
       with:
         go-version: ${{ matrix.go-version }}
 

go.mod

@@ -1,8 +1,14 @@
 module github.com/fyne-io/image
 
-go 1.14
+go 1.19
 
 require (
 	github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25
 	github.com/stretchr/testify v1.7.1
 )
+
+require (
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+)

xpm/fuzz_test.go

@@ -0,0 +1,32 @@
+package xpm
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// FuzzParsePanic runs a fuzzer to detect possible panics in the XPM
+// parser.  To run, use:
+//
+//	go test -fuzz=FuzzParsePanic
+func FuzzParsePanic(f *testing.F) {
+	matches, err := filepath.Glob("testdata/*.xpm")
+	if err != nil {
+		f.Fatalf("filepath.Glob: %v", err)
+	}
+	for _, m := range matches {
+		buf, err := os.ReadFile(m)
+		if err != nil {
+			f.Fatalf("os.ReadFile(%q): %v", m, err)
+		}
+		f.Add(buf)
+	}
+	f.Fuzz(func(t *testing.T, buf []byte) {
+		// It is expected that this may return an error during
+		// fuzzing, but we can at least make sure that it does
+		// not panic.
+		_, _ = Decode(bytes.NewReader(buf))
+	})
+}

xpm/testdata/colors.xpm

@@ -0,0 +1,28 @@
+/* XPM */
+static char * hexcolors_xpm[] = {
+/* width height ncolors chars_per_pixel */
+"15 17 5 1",
+/* colors */
+" 	s None	c None",
+".	c black	m black",
+"h	m white	c orange red",
+"@	c peach puff	m white",
+"#	c #FFF	m white",
+/* pixels */
+" .  .....      ",
+"  ..hhhhh.     ",
+"  .hhhh.hh.    ",
+"   ....@@h.    ",
+"   .@@@@@@.    ",
+"   .@.@@.@.    ",
+"   .@@@@@@..   ",
+"   .@.@@@@@@.  ",
+"   .@..@@@@.   ",
+"   .@@@@.@.    ",
+"   .....@@.    ",
+"    .@@@@@.    ",
+"    .@@@@@.    ",
+"  ..........   ",
+" ..###.####..  ",
+".#..........#. ",
+".#############."};

xpm/testdata/fuzz/FuzzParsePanic/48bee47275066ef2

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5\xb5 t ncolo1\", w* colors *\xb5")

xpm/testdata/fuzz/FuzzParsePanic/49dbcf54a1a83c8b

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\"1 1 1 1000000000\n\"\n\"")

xpm/testdata/fuzz/FuzzParsePanic/5ac08626c909a2f2

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\"1 1 1 1\"00\n\".\n\".00000")

xpm/testdata/fuzz/FuzzParsePanic/a003fd4d2de89c7a

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\"16 1 2 1\"\n\"0c #000 \n\"0c #000 \n\"0000000000000000\n\"0000000000000000")

xpm/testdata/fuzz/FuzzParsePanic/d89382570b33e29e

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\"1 9999999911 1 13\"\b")

xpm/testdata/fuzz/FuzzParsePanic/f275f91493d6574a

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\"1 1 1 1\"\n\"0c c")

xpm/testdata/fuzz/FuzzParsePanic/f3c56373a6c9cfd8

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\"1 0 0 000000\n\"")

xpm/xpm.go

@@ -2,6 +2,7 @@ package xpm
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"image"
 	"image/color"
@@ -10,6 +11,15 @@ import (
 	"strings"
 )
 
+// maxPixels is the maximum number of pixels that the parser supports,
+// to protect against prohibitively large memory allocations.  XPM
+// pixmaps tend to be small, it should not be possible to run into
+// this limit with real-life data.
+const maxPixels = 1024 * 1024 * 1024
+
+// ErrInvalidFormat indicates that the input image was malformatted.
+var ErrInvalidFormat = errors.New("invalid format")
+
 func parseXPM(data io.Reader) (image.Image, error) {
 	// Specification: https://www.xfree86.org/current/xpm.pdf
 	var colCount, charSize int
@@ -43,18 +53,19 @@ func parseXPM(data io.Reader) (image.Image, error) {
 				colors[id] = c
 			}
 		} else {
-			parsePixels(row, charSize, rowNum-colCount-1, colors, img)
+			err := parsePixels(row, charSize, rowNum-colCount-1, colors, img)
+			if err != nil {
+				return nil, err
+			}
 		}
 		rowNum++
 	}
 	return img, scan.Err()
 }
 
 func parseColor(data string, charSize int) (id string, c color.Color, err error) {
-	// TODO: parseColor should return a non-nil err in all error cases,
-	// instead of just returning and implicitly leaving err as nil.
 	if len(data) < charSize {
-		return
+		return "", nil, fmt.Errorf("%w: missing color specification", ErrInvalidFormat)
 	}
 
 	id = data[:charSize]
@@ -67,6 +78,10 @@ func parseColor(data string, charSize int) (id string, c color.Color, err error)
 		color := strings.Join(parts[:nki], " ")
 		parts = parts[nki:]
 
+		if color == "" {
+			return "", nil, fmt.Errorf("%w: missing color specification", ErrInvalidFormat)
+		}
+
 		switch key {
 		case "c":
 			c, err := stringToColor(color)
@@ -79,7 +94,7 @@ func parseColor(data string, charSize int) (id string, c color.Color, err error)
 			return "", nil, fmt.Errorf("unknown visual %q", key)
 		}
 	}
-	return
+	return "", nil, fmt.Errorf("%w: missing color specification", ErrInvalidFormat)
 }
 
 // nextKeyIndex returns the index of the next "c", "m", s", "g4", or
@@ -94,7 +109,7 @@ func nextKeyIndex(parts []string) int {
 	return len(parts)
 }
 
-func parseDimensions(data string) (w, h, i, j int, err error) {
+func parseDimensions(data string) (w, h, ncolors, cpp int, err error) {
 	if len(data) == 0 {
 		return
 	}
@@ -111,16 +126,41 @@ func parseDimensions(data string) (w, h, i, j int, err error) {
 	if err != nil {
 		return
 	}
-	i, err = strconv.Atoi(parts[2])
+	if w*h <= 0 {
+		err = fmt.Errorf("%w: empty or negative-sized image (%v x %v)", ErrInvalidFormat, w, h)
+		return
+	}
+	if w*h >= maxPixels {
+		err = fmt.Errorf("%w: too many pixels (%v x %v), want < %v", ErrInvalidFormat, w, h, maxPixels)
+		return
+	}
+	ncolors, err = strconv.Atoi(parts[2])
+	if err != nil {
+		return
+	}
+	if ncolors <= 0 {
+		err = fmt.Errorf("%w: ncolors <= 0: missing color palette", ErrInvalidFormat)
+		return
+	}
+	cpp, err = strconv.Atoi(parts[3])
 	if err != nil {
 		return
 	}
-	j, err = strconv.Atoi(parts[3])
+	if cpp <= 0 {
+		err = fmt.Errorf("%w: characters per pixel <= 0", ErrInvalidFormat)
+		return
+	}
 	return
 }
 
-func parsePixels(row string, charSize int, pixRow int, colors map[string]color.Color, img *image.NRGBA) {
+func parsePixels(row string, charSize int, pixRow int, colors map[string]color.Color, img *image.NRGBA) error {
+	if len(row) < charSize*(img.Stride/4) {
+		return fmt.Errorf("%w: missing pixel data", ErrInvalidFormat)
+	}
 	off := pixRow * img.Stride
+	if len(img.Pix) < off+img.Stride {
+		return fmt.Errorf("%w: too much pixel data", ErrInvalidFormat)
+	}
 	chPos := 0
 	for i := 0; i < img.Stride/4; i++ {
 		id := row[chPos : chPos+charSize]
@@ -137,6 +177,7 @@ func parsePixels(row string, charSize int, pixRow int, colors map[string]color.C
 		img.Pix[pos+3] = uint8(a)
 		chPos += charSize
 	}
+	return nil
 }
 
 func stringToColor(data string) (color.Color, error) {
@@ -159,13 +200,13 @@ func stringToColor(data string) (color.Color, error) {
 			// See https://gitlab.freedesktop.org/xorg/lib/libxpm/-/issues/7
 			r, g, b = 0x10*r, 0x10*g, 0x10*b
 		default:
-			return nil, fmt.Errorf("invalid hex color %q", data)
+			return nil, fmt.Errorf("%w: invalid hex color %q", ErrInvalidFormat, data)
 		}
 		return color.NRGBA{r, g, b, 0xff}, err
 	default:
 		c, ok := x11colors[data]
 		if !ok {
-			return nil, fmt.Errorf("invalid X11 color %q", data)
+			return nil, fmt.Errorf("%w: invalid X11 color %q", ErrInvalidFormat, data)
 		}
 		return c, nil
 	}

xpm/xpm_test.go

@@ -5,36 +5,60 @@ import (
 	"image/color"
 	_ "image/png"
 	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 )
 
 func TestParse(t *testing.T) {
-	r, err := os.Open("testdata/blarg.xpm")
-	assert.Nil(t, err)
-	defer r.Close()
-	img, err := parseXPM(r)
-	assert.Nil(t, err)
-	assert.Equal(t, 0, img.Bounds().Min.X)
-	assert.Equal(t, 0, img.Bounds().Min.Y)
-	assert.Equal(t, 16, img.Bounds().Max.X)
-	assert.Equal(t, 7, img.Bounds().Max.Y)
-
-	r, err = os.Open("testdata/blarg.png")
+	matches, err := filepath.Glob("testdata/*.png")
 	if err != nil {
-		t.Error(err)
+		t.Fatalf("filepath.Glob: %v", err)
 	}
-
-	golden, _, err := image.Decode(r)
-	if err != nil {
-		t.Error(err)
+	if len(matches) == 0 {
+		t.Fatalf("Missing examples and golden files")
 	}
+	for _, pngName := range matches {
+		var (
+			pngName  = pngName
+			xpmName  = pngName[:len(pngName)-4] + ".xpm"
+			testName = filepath.Base(pngName[:len(pngName)-4])
+		)
+		t.Run(testName, func(t *testing.T) {
+			r, err := os.Open(xpmName)
+			if err != nil {
+				t.Fatalf("os.Open(%q): %v", xpmName, err)
+			}
+			defer r.Close()
+
+			img, err := parseXPM(r)
+			assert.Nil(t, err)
+
+			r, err = os.Open(pngName)
+			if err != nil {
+				t.Fatalf("os.Open(%q): %v", pngName, err)
+			}
+			defer r.Close()
+
+			golden, _, err := image.Decode(r)
+			if err != nil {
+				t.Fatalf("image.Decode() for %q: %v", pngName, err)
+			}
+			assert.Equal(t, golden.Bounds(), img.Bounds())
 
-	pixCount := len(golden.(*image.RGBA).Pix)
-	assert.Equal(t, pixCount, len(img.(*image.NRGBA).Pix))
-	for i := 0; i < pixCount; i++ {
-		assert.Equal(t, golden.(*image.RGBA).Pix[i], img.(*image.NRGBA).Pix[i])
+			b := golden.Bounds()
+			for x := b.Min.X; x < b.Max.X; x++ {
+				for y := b.Min.Y; y < b.Max.Y; y++ {
+					iR, iG, iB, iA := img.At(x, y).RGBA()
+					gR, gG, gB, gA := golden.At(x, y).RGBA()
+					assert.Equal(t, iR, gR, "red at (%v, %v)", x, y)
+					assert.Equal(t, iG, gG, "green at (%v, %v)", x, y)
+					assert.Equal(t, iB, gB, "blue at (%v, %v)", x, y)
+					assert.Equal(t, iA, gA, "alpha at (%v, %v)", x, y)
+				}
+			}
+		})
 	}
 }