New API for encoding bitmaps during serialization.

include/core/SkPicture.h

Index: include/core/SkPicture.h
diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index b2c2b62edec4ee3684dc4ef4ef3129a1e29f2ad8..f3057016e19443c9e5be961e9ac7cca264cee4b0 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -15,6 +15,7 @@
 
 class SkBBoxHierarchy;
 class SkCanvas;
+class SkData;
 class SkPicturePlayback;
 class SkPictureRecord;
 class SkStream;
@@ -168,14 +169,28 @@ public:
     */
     int height() const { return fHeight; }
 
+    enum RecordPixelRefOffset {
+        kYes_RecordPixelRefOffset,
+        kNo_RecordPixelRefOffset,
+    };
+
     /**
-     *  Function to encode an SkBitmap to an SkWStream. A function with this
-     *  signature can be passed to serialize() and SkOrderedWriteBuffer. The
-     *  function should return true if it succeeds. Otherwise it should return
-     *  false so that SkOrderedWriteBuffer can switch to another method of
-     *  storing SkBitmaps.
+     *  Function to encode an SkBitmap to an SkData. A function with this
+     *  signature can be passed to serialize() and SkOrderedWriteBuffer.
+     *  Returning NULL will tell the SkOrderedWriteBuffer to use
+     *  SkBitmap::flatten() to store the bitmap.
+     *  @param RecordPixelRefOffset Output parameter, telling the
+     *      SkOrderedWriteBuffer whether to record the bitmap's pixelRefOffset.
+     *      If set to kYes_RecordPixelRefOffset, the returned SkData contains
+     *      compressed data containing the entire image, so the pixelRefOffset
+     *      should also be recorded to the stream. If set to
+     *      kNo_RecordPixelRefOffset, only the extracted subset is written to
+     *      the returned SkData, so the offset should not be written to the
+     *      stream.
+     *  @return SkData If non-NULL, holds encoded data representing the passed
+     *      in bitmap. The caller is responsible for calling unref().
      */
-    typedef bool (*EncodeBitmap)(SkWStream*, const SkBitmap&);
+    typedef SkData* (*EncodeBitmap)(RecordPixelRefOffset*, const SkBitmap&);

[scroggo, 2013/05/20 19:50:52]

Mike, you mentioned perhaps wanting to use the same signature in other places.
In that case, I think RecordPixelRefOffset should be changed to something more
general. Maybe ContainsLargerImage, or something that makes it clear that the
SkData represents a superset of the pixels used by the SkBitmap.

 
     /**
      *  Serialize to a stream. If non NULL, encoder will be used to encode