Preventing division by 0

src/core/SkXfermode.cpp

 
 /*
  * 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.
  */
 
 
 #include "SkXfermode.h"
@@ skipping 450 matching lines @@
         setSaturationComponents(g, b, r, s);
     } else {
         setSaturationComponents(b, g, r, s);
     }
 }
 
 static inline void clipColor(int* r, int* g, int* b, int a) {
     int L = Lum(*r, *g, *b);
     int n = minimum(*r, *g, *b);
     int x = maximum(*r, *g, *b);
-    if(n < 0) {
-       *r = L + SkMulDiv(*r - L, L, L - n);
-       *g = L + SkMulDiv(*g - L, L, L - n);
-       *b = L + SkMulDiv(*b - L, L, L - n);
+    int denom;
+    if ((n < 0) && (denom = L - n)) { // Compute denom and make sure it's non zero
+       *r = L + SkMulDiv(*r - L, L, denom);
+       *g = L + SkMulDiv(*g - L, L, denom);
+       *b = L + SkMulDiv(*b - L, L, denom);
     }
 
-    if (x > a) {
-       *r = L + SkMulDiv(*r - L, a - L, x - L);
-       *g = L + SkMulDiv(*g - L, a - L, x - L);
-       *b = L + SkMulDiv(*b - L, a - L, x - L);
+    if ((x > a) && (denom = x - L)) { // Compute denom and make sure it's non zero
+       int numer = a - L;
+       *r = L + SkMulDiv(*r - L, numer, denom);
+       *g = L + SkMulDiv(*g - L, numer, denom);
+       *b = L + SkMulDiv(*b - L, numer, denom);
     }
 }
 
 static inline void SetLum(int* r, int* g, int* b, int a, int l) {
   int d = l - Lum(*r, *g, *b);
   *r +=  d;
   *g +=  d;
   *b +=  d;
 
   clipColor(r, g, b, a);
@@ skipping 1477 matching lines @@
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkProcCoeffXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkClearXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkSrcXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkDstInXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkDstOutXfermode)
 #if !SK_ARM_NEON_IS_NONE
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkNEONProcCoeffXfermode)
 #endif
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END