Add special case circle blur for Ganesh

include/core/SkColor.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkColor_DEFINED
 #define SkColor_DEFINED
 
@@ skipping 121 matching lines @@
         hsv[2] is Value [0...1]
     If hsv values are out of range, they are pinned.
     @param hsv  3 element array which holds the input HSV components.
     @return the resulting argb color
 */
 static inline SkColor SkHSVToColor(const SkScalar hsv[3])
 {
     return SkHSVToColor(0xFF, hsv);
 }
 
+static inline U8CPU SkUnitScalarToByte(SkScalar x) {
+    if (x < 0) {
+        return 0;
+    }
+    if (x >= SK_Scalar1) {
+        return 255;
+    }
+    return SkScalarToFixed(x) >> 8;

[bsalomon, 2015/09/11 13:05:46]

Maybe SkUnitScalarClampToByte(). Many of our SkXToY functions just assert that
the X fits in the Y.

[robertphillips, 2015/09/11 15:55:34]

Done.

[reed1, 2015/09/11 18:47:11]

Independent of the clamping question...

This is a recent hot-topic for me. What *is* the right scaling function?

1. round(x * 255)
2. floor(x * 255.9999)

The current impl is "close" to #2, but not exactly either.

[robertphillips, 2015/09/15 16:35:06]

It seems like some pinned version of #2 would be best for this use case.

+}
+
 ////////////////////////////////////////////////////////////////////////
 
 /** 32 bit ARGB color value, premultiplied. The byte order for this value is
     configuration dependent, matching the format of kARGB32 bitmaps. This is different
     from SkColor, which is nonpremultiplied, and is always in the same byte order.
 */
 typedef uint32_t SkPMColor;
 
 /** Return a SkPMColor value from unpremultiplied 8 bit component values
 */
 SK_API SkPMColor SkPreMultiplyARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b);
 /** Return a SkPMColor value from a SkColor value. This is done by multiplying the color
     components by the color's alpha, and by arranging the bytes in a configuration
     dependent order, to match the format of kARGB32 bitmaps.
 */
 SK_API SkPMColor SkPreMultiplyColor(SkColor c);
 
 /** Define a function pointer type for combining two premultiplied colors
 */
 typedef SkPMColor (*SkXfermodeProc)(SkPMColor src, SkPMColor dst);
 
 #endif