bmp: support to decode 8-bit format with up to 256 color palette
If colorUsed is 0, the number of palette is 2 to the power of bit per pixel.
testdata/colormap-251.{bmp,png} are added for testing 8-bit format with colorUsed less than 256.
testdata/colormap-0.{bmp,png} are added for testing 8-bit format with colorUsed 0.
Fixes golang/go#61240
Change-Id: I1a627a570f667874a91c517f4a771e9e97d2af6b
Reviewed-on: https://go-review.googlesource.com/c/image/+/508575
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Nigel Tao <nigeltao@golang.org>
Reviewed-by: Nigel Tao (INACTIVE; USE @golang.org INSTEAD) <nigeltao@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Nigel Tao <nigeltao@golang.org>
diff --git a/bmp/reader.go b/bmp/reader.go
index e165c2e..1939c11 100644
--- a/bmp/reader.go
+++ b/bmp/reader.go
@@ -191,14 +191,22 @@
}
switch bpp {
case 8:
- if offset != fileHeaderLen+infoLen+256*4 {
+ colorUsed := readUint32(b[46:50])
+ // If colorUsed is 0, it is set to the maximum number of colors for the given bpp, which is 2^bpp.
+ if colorUsed == 0 {
+ colorUsed = 256
+ } else if colorUsed > 256 {
return image.Config{}, 0, false, false, ErrUnsupported
}
- _, err = io.ReadFull(r, b[:256*4])
+
+ if offset != fileHeaderLen+infoLen+colorUsed*4 {
+ return image.Config{}, 0, false, false, ErrUnsupported
+ }
+ _, err = io.ReadFull(r, b[:colorUsed*4])
if err != nil {
return image.Config{}, 0, false, false, err
}
- pcm := make(color.Palette, 256)
+ pcm := make(color.Palette, colorUsed)
for i := range pcm {
// BMP images are stored in BGR order rather than RGB order.
// Every 4th byte is padding.
diff --git a/bmp/reader_test.go b/bmp/reader_test.go
index 8325f34..003d64f 100644
--- a/bmp/reader_test.go
+++ b/bmp/reader_test.go
@@ -41,6 +41,8 @@
func TestDecode(t *testing.T) {
testCases := []string{
"colormap",
+ "colormap-0",
+ "colormap-251",
"video-001",
"yellow_rose-small",
"yellow_rose-small-v5",
diff --git a/testdata/colormap-0.bmp b/testdata/colormap-0.bmp
new file mode 100644
index 0000000..03a9a6a
--- /dev/null
+++ b/testdata/colormap-0.bmp
Binary files differ
diff --git a/testdata/colormap-0.png b/testdata/colormap-0.png
new file mode 100644
index 0000000..7a6b866
--- /dev/null
+++ b/testdata/colormap-0.png
Binary files differ
diff --git a/testdata/colormap-251.bmp b/testdata/colormap-251.bmp
new file mode 100644
index 0000000..6b8dad6
--- /dev/null
+++ b/testdata/colormap-251.bmp
Binary files differ
diff --git a/testdata/colormap-251.png b/testdata/colormap-251.png
new file mode 100644
index 0000000..81c489c
--- /dev/null
+++ b/testdata/colormap-251.png
Binary files differ
