WIP: Implement APNG

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 9c5615bfd8ad515126a9c1561ad7764344606de5..b94cd42566073d076472e9854219491a91b9d129 100644
--- a/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
+++ b/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
@@ -218,6 +218,47 @@ class PLATFORM_EXPORT ImageFrame final {
     *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 void blendRGBARaw(PixelData* dest,
+                           unsigned r,
+                           unsigned g,
+                           unsigned b,
+                           unsigned a);
+
+  // Blend the pixel, without premultiplication, in |src| over |dst| and
+  // overwrite |src| with the result.
+  static void blendSrcOverDstRaw(PixelData* src, PixelData dst);
+
+  // Blend the RGBA pixel provided by |r|, |g|, |b|, |a| over the pixel in
+  // |dest| and overwrite |dest| with the result. Premultiply the pixel values
+  // before blending.
+  static inline void blendRGBAPremultiply(PixelData* dest,
+                                          unsigned r,
+                                          unsigned g,
+                                          unsigned b,
+                                          unsigned a) {
+    // If the new pixel is completely transparent, no operation is necessary
+    // since |dest| contains the background pixel.
+    if (a == 0x0)
+      return;
+
+    // If the new pixel is opaque, no need for blending - just write the pixel.
+    if (a == 0xFF)
+      return setRGBAPremultiply(dest, r, g, b, a);
+
+    PixelData src;
+    setRGBAPremultiply(&src, r, g, b, a);
+    *dest = SkPMSrcOver(src, *dest);
+  }
+
+  // Blend the pixel in |src| over |dst| and overwrite |src| with the result.
+  // This assumes the pixel values in |src| are already premultiplied.
+  static inline void blendSrcOverDstPremultiplied(PixelData* src,
+                                                  PixelData dst) {
+    *src = SkPMSrcOver(*src, dst);
+  }
+
   // Notifies the SkBitmap if any pixels changed and resets the flag.
   inline void notifyBitmapIfPixelsChanged() {
     if (m_pixelsChanged)