1 files changed, 13 insertions, 0 deletions
diff --git a/include/core/SkBitmap.h b/include/core/SkBitmap.h
index 1def198..84d069c 100644
--- a/include/core/SkBitmap.h
+++ b/include/core/SkBitmap.h
@@ -404,6 +404,19 @@ public:
         this->extractAlpha(dst, paint, NULL, offset);
     }
 
+    /** Set dst to contain alpha layer of this bitmap. If destination bitmap
+        fails to be initialized, e.g. because allocator can't allocate pixels
+        for it, dst will be resetted (zero width and height, no pixels).
+
+        @param dst The bitmap to be filled with alpha layer
+        @param paint The paint to draw with
+        @param allocator Allocator used to allocate the pixelref for the dst
+                         bitmap. If this is null, the standard HeapAllocator
+                         will be used.
+        @param offset If not null, it is set to top-left coordinate to position
+                      the returned bitmap so that it visually lines up with the
+                      original
+    */
     void extractAlpha(SkBitmap* dst, const SkPaint* paint, Allocator* allocator,
                       SkIPoint* offset) const;