Make image decoders faster by refactoring hot loops that fills the lines of ImageFrame.

Source/core/platform/image-decoders/ImageDecoder.h

Index: Source/core/platform/image-decoders/ImageDecoder.h
diff --git a/Source/core/platform/image-decoders/ImageDecoder.h b/Source/core/platform/image-decoders/ImageDecoder.h
index 591548dc1b66be8314bbdbc14affef93a64acc24..9a05e212b8df0c6a2f95eb74aef81250af39a320 100644
--- a/Source/core/platform/image-decoders/ImageDecoder.h
+++ b/Source/core/platform/image-decoders/ImageDecoder.h
@@ -175,24 +175,61 @@ namespace WebCore {
             return  (fixed * v) >> fixPointShift;
         }
 
+        inline void setRGB(PixelData* dest, unsigned r, unsigned g, unsigned b)
+        {
+            checkAddress(dest);
+            *dest = SkPackARGB32NoCheck(255, r, g, b);
+        }
+
         inline void setRGBA(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
         {
-            if (m_premultiplyAlpha && a < 255) {
-                if (!a) {
-                    *dest = 0;
-                    return;
-                }
+            if (m_premultiplyAlpha)
+                setRGBAPremultiply(dest, a, r, g, b);
+            else
+                setRGBANoPremultiply(dest, a, r, g, b);
+        }
+
+        inline void setRGBAPremultiply(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
+        {
+            checkAddress(dest);
+            ASSERT(m_premultiplyAlpha);
 
+            if (!a) {
+                *dest = 0;
+                return;
+            }
+            if (a < 255) {
                 unsigned alphaMult = a * fixPointMult;
                 r = fixPointUnsignedMultiply(r, alphaMult);
                 g = fixPointUnsignedMultiply(g, alphaMult);
                 b = fixPointUnsignedMultiply(b, alphaMult);
             }
+
             // Call the "NoCheck" version since we may deliberately pass non-premultiplied
             // values, and we don't want an assert.
             *dest = SkPackARGB32NoCheck(a, r, g, b);
         }
 
+        inline void setRGBANoPremultiply(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
+        {
+            checkAddress(dest);
+            ASSERT(!m_premultiplyAlpha);
+
+            *dest = SkPackARGB32NoCheck(a, r, g, b);
+        }
+
+        inline void setInvertedCMYK(PixelData* dest, unsigned c, unsigned m, unsigned y, unsigned k)
+        {
+            checkAddress(dest);
+
+            unsigned kMult = k * fixPointMult;
+            unsigned r = fixPointUnsignedMultiply(c, kMult);
+            unsigned g = fixPointUnsignedMultiply(m, kMult);
+            unsigned b = fixPointUnsignedMultiply(y, kMult);
+
+            *dest = SkPackARGB32NoCheck(255, r, g, b);
+        }
+
     private:
         int width() const
         {
@@ -204,6 +241,11 @@ namespace WebCore {
             return m_bitmap->bitmap().height();
         }
 
+        void checkAddress(PixelData* address)

[Peter Kasting, 2013/06/12 18:47:07]

I would just omit this.  The previous code had a setRGBA() function that wrote
to a pointer without checking and I think it's OK for the new functions to do so
too.  This just adds verbosity and debug-mode slowness, callers should be doing
something legal here.

+        {
+            ASSERT(getAddr(0, 0) <= address && address <= getAddr(0, 0) + width() * height() * m_hasAlpha ? 4 : 3);
+        }
+
         RefPtr<NativeImageSkia> m_bitmap;
         SkBitmap::Allocator* m_allocator;
         bool m_hasAlpha;