Ensure the Gaussian tail of circle blurs goes to zero.

src/effects/GrCircleBlurFragmentProcessor.cpp

 
 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrCircleBlurFragmentProcessor.h"
 
@@ skipping 191 matching lines @@
     SkAutoTArray<float> halfKernel(kernelWH*kernelWH/2);
 
     make_half_kernel(halfKernel.get(), kernelWH, sigma);
 
     float offset;
     int numSteps;
 
     compute_profile_offset_and_size(halfWH, sigma, &offset, &numSteps);
 
     uint8_t* weights = new uint8_t[numSteps];
-    for (int i = 0; i < numSteps; ++i) {
+    for (int i = 0; i < numSteps - 1; ++i) {
         weights[i] = eval_at(offset+i, halfWH, halfKernel.get(), kernelWH);
     }
+    // Ensure the tail of the Gaussian goes to zero.
+    weights[numSteps-1] = 0;
 
     return weights;
 }
 
 GrTexture* GrCircleBlurFragmentProcessor::CreateCircleBlurProfileTexture(
                                                                 GrTextureProvider* textureProvider,
                                                                 const SkRect& circle,
                                                                 float sigma,
                                                                 float* offset) {
     float halfWH = circle.width() / 2.0f;
@@ skipping 32 matching lines @@
 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrCircleBlurFragmentProcessor);
 
 const GrFragmentProcessor* GrCircleBlurFragmentProcessor::TestCreate(GrProcessorTestData* d) {
     SkScalar wh = d->fRandom->nextRangeScalar(100.f, 1000.f);
     SkScalar sigma = d->fRandom->nextRangeF(1.f,10.f);
     SkRect circle = SkRect::MakeWH(wh, wh);
     return GrCircleBlurFragmentProcessor::Create(d->fContext->textureProvider(), circle, sigma);
 }
 
 #endif