SkColorCubeFilter: require alpha == 0xFF.

src/opts/SkColorCubeFilter_opts.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SkColorCubeFilter_opts_DEFINED
 #define SkColorCubeFilter_opts_DEFINED
 
 #include "SkColor.h"
 #include "SkPMFloat.h"
 #include "SkUnPreMultiply.h"
@@ skipping 35 matching lines @@
                    g1b0(g1*b0),
                    g1b1(g1*b1);
 
         const int i00 = (colorToIndex[0][g] + colorToIndex[0][b] * dim) * dim;
         const int i01 = (colorToIndex[0][g] + colorToIndex[1][b] * dim) * dim;
         const int i10 = (colorToIndex[1][g] + colorToIndex[0][b] * dim) * dim;
         const int i11 = (colorToIndex[1][g] + colorToIndex[1][b] * dim) * dim;
 
         SkPMFloat color(0);
 
         for (int x = 0; x < 2; ++x) {

[Noel Gordon, 2015/08/20 07:10:07]

Possible followup: unroll this loop.  Mac air goes from 129ms -> 119ms for me in
that case.

             const int ix = colorToIndex[x][r];
 
             const SkColor lutColor00 = colorCube[ix + i00];
             const SkColor lutColor01 = colorCube[ix + i01];
             const SkColor lutColor10 = colorCube[ix + i10];
             const SkColor lutColor11 = colorCube[ix + i11];
 
-            Sk4f  sum = SkPMFloat::FromBGRx(lutColor00) * g0b0;
-            sum = sum + SkPMFloat::FromBGRx(lutColor01) * g0b1;
-            sum = sum + SkPMFloat::FromBGRx(lutColor10) * g1b0;
-            sum = sum + SkPMFloat::FromBGRx(lutColor11) * g1b1;
+            Sk4f  sum = SkPMFloat::FromOpaqueColor(lutColor00) * g0b0;
+            sum = sum + SkPMFloat::FromOpaqueColor(lutColor01) * g0b1;
+            sum = sum + SkPMFloat::FromOpaqueColor(lutColor10) * g1b0;
+            sum = sum + SkPMFloat::FromOpaqueColor(lutColor11) * g1b1;
 
             color = color + sum * Sk4f((float)colorToFactors[x][r]);
         }
 
         if (a != 255) {
             color = color * Sk4f(a * 1.0f/255);
         }
 
         dst[i] = color.round();
 
         ptr_dst[SK_A32_SHIFT / 8] = a;
         ptr_dst += 4;
     }
 }
 
 }  // namespace SK_OPTS NS
 
 #endif  // SkColorCubeFilter_opts_DEFINED