Always use a color table with 256 colors

Speculative fix for skbug.com/5883

We are hitting an assert (which I have not been able to repro - still
need to get the skp that triggers it) because we are trying to read
beyond the end of the color table. We use 8-bit indices, so 256 should
be enough to prevent going beyond the end. There is only one case when
we use a smaller color table - when it is a dummy. Make the dummy full
size.

NOTREECHECKS=true

BUG=skia:5883
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2452673002

Review-Url: https://codereview.chromium.org/2452673002

diff --git a/src/codec/SkGifCodec.cpp b/src/codec/SkGifCodec.cpp
index 263004b6cdea084ba93004dbc2fa4d0a71804a1c..e55f6f3a6e46d959d6ceb9b9b0999e83e2828ffa 100644 (file)
--- a/src/codec/SkGifCodec.cpp
+++ b/src/codec/SkGifCodec.cpp
@@ -37,6 +37,7 @@
 #include "SkGifCodec.h"
 #include "SkStream.h"
 #include "SkSwizzler.h"
+#include "SkUtils.h"
 
 #include <algorithm>
 
@@ -143,9 +144,10 @@ void SkGifCodec::initializeColorTable(const SkImageInfo& dstInfo, size_t frameIn
     fCurrColorTable = fReader->getColorTable(dstInfo.colorType(), frameIndex);
     fCurrColorTableIsReal = fCurrColorTable;
     if (!fCurrColorTable) {
-        // This is possible for an empty frame. Create a dummy with one value (transparent).
-        SkPMColor color = SK_ColorTRANSPARENT;
-        fCurrColorTable.reset(new SkColorTable(&color, 1));
+        // This is possible for an empty frame. Create a dummy with all transparent.
+        SkPMColor colors[MAX_COLORS];
+        sk_memset32(colors, SK_ColorTRANSPARENT, MAX_COLORS);
+        fCurrColorTable.reset(new SkColorTable(colors, 256));
     }
 
     if (inputColorCount) {