Check for divide by zero in fill_in_2D_gaussian_kernel

Same change as the 1D one, but now with more dimensions!!

Bug: skia:7769
Change-Id: I152031780ab71ba106d4fa65d52960ec4358274e
Reviewed-on: https://skia-review.googlesource.com/118262
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>

2 files changed, 14 insertions, 3 deletions

diff --git a/src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp b/src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp
index 121e225796..fdd4990328 100644
--- a/src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp
+++ b/src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp
@@ -177,7 +177,7 @@ void GrGLConvolutionEffect::GenKey(const GrProcessor& processor, const GrShaderC
 
 ///////////////////////////////////////////////////////////////////////////////
 static void fill_in_1D_gaussian_kernel(float* kernel, int width, float gaussianSigma, int radius) {
-    float twoSigmaSqrd = 2.0f * gaussianSigma * gaussianSigma;
+    const float twoSigmaSqrd = 2.0f * gaussianSigma * gaussianSigma;
     if (SkScalarNearlyZero(twoSigmaSqrd, SK_ScalarNearlyZero)) {
         for (int i = 0; i < width; ++i) {
             kernel[i] = 0.0f;
diff --git a/src/gpu/effects/GrMatrixConvolutionEffect.cpp b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
index ffbcf500ab..56b012afe5 100644
--- a/src/gpu/effects/GrMatrixConvolutionEffect.cpp
+++ b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
@@ -215,8 +215,19 @@ bool GrMatrixConvolutionEffect::onIsEqual(const GrFragmentProcessor& sBase) cons
 static void fill_in_2D_gaussian_kernel(float* kernel, int width, int height,
                                        SkScalar sigmaX, SkScalar sigmaY) {
     SkASSERT(width * height <= MAX_KERNEL_SIZE);
-    const float sigmaXDenom = 1.0f / (2.0f * SkScalarToFloat(SkScalarSquare(sigmaX)));
-    const float sigmaYDenom = 1.0f / (2.0f * SkScalarToFloat(SkScalarSquare(sigmaY)));
+    const float twoSigmaSqrdX = 2.0f * SkScalarToFloat(SkScalarSquare(sigmaX));
+    const float twoSigmaSqrdY = 2.0f * SkScalarToFloat(SkScalarSquare(sigmaY));
+
+    if (SkScalarNearlyZero(twoSigmaSqrdX, SK_ScalarNearlyZero) ||
+        SkScalarNearlyZero(twoSigmaSqrdY, SK_ScalarNearlyZero)) {
+        for (int i = 0; i < width * height; ++i) {
+            kernel[i] = 0.0f;
+        }
+        return;
+    }
+
+    const float sigmaXDenom = 1.0f / twoSigmaSqrdX;
+    const float sigmaYDenom = 1.0f / twoSigmaSqrdY;
     const int xRadius = width / 2;
     const int yRadius = height / 2;