Animated PNG implementation

third_party/WebKit/Source/platform/image-decoders/ImageFrame.h

Index: third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h b/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
index 574b66df089049e866ddfaf8c9bc811a30e10619..9ff7a3ba439efd0436aaba700ae739edbf4733f7 100644
--- a/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
+++ b/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
@@ -218,6 +218,51 @@ class PLATFORM_EXPORT ImageFrame final {
     *dest = SkPackARGB32NoCheck(a, r, g, b);
   }
 
+  inline void overRGBAPremultiply(PixelData* dest,
+                                  unsigned r,
+                                  unsigned g,
+                                  unsigned b,
+                                  unsigned a) {
+    enum FractionControl { RoundFractionControl = 257 * 128 };
+
+    if (!a)
+      return;
+
+    if (a < 255) {
+      unsigned alpha = a * 257;
+      r = (r * alpha + RoundFractionControl) >> 16;
+      g = (g * alpha + RoundFractionControl) >> 16;
+      b = (b * alpha + RoundFractionControl) >> 16;
+      *dest = SkPMSrcOver(SkPackARGB32NoCheck(a, r, g, b), *dest);
+    } else {
+      *dest = SkPackARGB32NoCheck(a, r, g, b);
+    }
+  }
+
+  inline void overRGBARaw(PixelData* dest,
+                          unsigned r,
+                          unsigned g,
+                          unsigned b,
+                          unsigned a) {
+    if (!a)
+      return;
+
+    unsigned aDest = SkGetPackedA32(*dest);
+    if (aDest && a < 255) {
+      unsigned u = a * 255;
+      unsigned v = (255 - a) * aDest;
+      unsigned alpha = u + v;
+      unsigned rDest = SkGetPackedR32(*dest);
+      unsigned gDest = SkGetPackedG32(*dest);
+      unsigned bDest = SkGetPackedB32(*dest);
+      a = (alpha + (alpha >> 8) + 1) >> 8;
+      r = (r * u + rDest * v) / alpha;
+      g = (g * u + gDest * v) / alpha;
+      b = (b * u + bDest * v) / alpha;
+    }
+    *dest = SkPackARGB32NoCheck(a, r, g, b);
+  }
+
   // Blend the RGBA pixel provided by |r|, |g|, |b|, |a| over the pixel in
   // |dest|, without premultiplication, and overwrite |dest| with the result.
   static inline void blendRGBARaw(PixelData* dest,