Changeset 102519 in webkit

Timestamp:

Dec 10, 2011 1:54:37 AM (12 years ago)

Author:

noel.gordon@gmail.com

Message:

WebPImageDecoder progressive decodes fail to decode valid images
​https://bugs.webkit.org/show_bug.cgi?id=74062

Reviewed by Adam Barth.

The WEBP header is followed by a so-called P0 header, then some data to
decode. If a partial P0 header is received during progressive decodes,
WebPIDecGetRGB() returns false; that makes the decoder enter the failed
state, no image appears on the page.

James Zern (webp) recommended the following via e-mail:

WebPIUpdate() validates input data, and will return an error status for
malformed data (bit-stream error, invalid data). Otherwise, it returns
OK or SUSPENDED. OK means that decoding is done/complete/no-error, and
SUSPENDED means more input data is needed to complete decoding. A NULL
return from WebPIDecGetRGB() is valid at this time due to a partial P0,
and should not be interpreted as a decoding failure.

No new tests. Not something DumpRenderTree can easily test.

• platform/image-decoders/webp/WEBPImageDecoder.cpp:

(WebCore::WEBPImageDecoder::decode): A NULL WebPIDecGetRGB() return is
acceptable here. Return false instead of failing the decoder.

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/image-decoders/webp/WEBPImageDecoder.cpp (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2011-12-10  Noel Gordon  <noel.gordon@gmail.com>
+
+        WebPImageDecoder progressive decodes fail to decode valid images
+        https://bugs.webkit.org/show_bug.cgi?id=74062
+
+        Reviewed by Adam Barth.
+
+        The WEBP header is followed by a so-called P0 header, then some data to
+        decode.  If a partial P0 header is received during progressive decodes,
+        WebPIDecGetRGB() returns false; that makes the decoder enter the failed
+        state, no image appears on the page.
+
+        James Zern (webp) recommended the following via e-mail:
+
+        WebPIUpdate() validates input data, and will return an error status for
+        malformed data (bit-stream error, invalid data).  Otherwise, it returns
+        OK or SUSPENDED.  OK means that decoding is done/complete/no-error, and
+        SUSPENDED means more input data is needed to complete decoding.  A NULL
+        return from WebPIDecGetRGB() is valid at this time due to a partial P0,
+        and should not be interpreted as a decoding failure.
+
+        No new tests. Not something DumpRenderTree can easily test.
+
+        * platform/image-decoders/webp/WEBPImageDecoder.cpp:
+        (WebCore::WEBPImageDecoder::decode):  A NULL WebPIDecGetRGB() return is
+        acceptable here.  Return false instead of failing the decoder.
+
 2011-12-09  Benjamin Poulain  <bpoulain@apple.com>
 

trunk/Source/WebCore/platform/image-decoders/webp/WEBPImageDecoder.cpp

@@ -135 +135 @@
             return setFailed();
         if (!WebPIDecGetRGB(m_decoder, &newLastVisibleRow, 0, 0, 0))
-            return setFailed();
+            return false;
         ASSERT(newLastVisibleRow >= 0);
         ASSERT(newLastVisibleRow <= height);