ARM Skia NEON patches - 07 - Equation simplification

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 382 matching lines @@
     int sa = SkGetPackedA32(src);
     int da = SkGetPackedA32(dst);
     int a = srcover_byte(sa, da);
     int r = difference_byte(SkGetPackedR32(src), SkGetPackedR32(dst), sa, da);
     int g = difference_byte(SkGetPackedG32(src), SkGetPackedG32(dst), sa, da);
     int b = difference_byte(SkGetPackedB32(src), SkGetPackedB32(dst), sa, da);
     return SkPackARGB32(a, r, g, b);
 }
 
 // kExclusion_Mode
-static inline int exclusion_byte(int sc, int dc, int sa, int da) {
+static inline int exclusion_byte(int sc, int dc, int, int) {
     // this equations is wacky, wait for SVG to confirm it
-    int r = sc * da + dc * sa - 2 * sc * dc + sc * (255 - da) + dc * (255 - sa);
+    //int r = sc * da + dc * sa - 2 * sc * dc + sc * (255 - da) + dc * (255 - sa);
+
+    // The above equation can be simplified as follows
+    int r = 255*(sc + dc) - 2 * sc * dc;
     return clamp_div255round(r);
 }
 static SkPMColor exclusion_modeproc(SkPMColor src, SkPMColor dst) {
     int sa = SkGetPackedA32(src);
     int da = SkGetPackedA32(dst);
     int a = srcover_byte(sa, da);
     int r = exclusion_byte(SkGetPackedR32(src), SkGetPackedR32(dst), sa, da);
     int g = exclusion_byte(SkGetPackedG32(src), SkGetPackedG32(dst), sa, da);
     int b = exclusion_byte(SkGetPackedB32(src), SkGetPackedB32(dst), sa, da);
     return SkPackARGB32(a, r, g, b);
@@ skipping 1552 matching lines @@
     return proc16;
 }
 
 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)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END