Sk4px: Difference and Exclusion

src/core/Sk4px.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef Sk4px_DEFINED
 #define Sk4px_DEFINED
 
 #include "SkNx.h"
 #include "SkColor.h"
 
 // 1, 2 or 4 SkPMColors, generally vectorized.
 class Sk4px : public Sk16b {
 public:
     Sk4px(SkAlpha a) : INHERITED(a) {} // Duplicate 16x: a    -> aaaa aaaa aaaa aaaa
     Sk4px(SkPMColor);                  // Duplicate 4x:  argb -> argb argb argb argb
     Sk4px(const Sk16b& v) : INHERITED(v) {}
 
     Sk4px alphas() const;  // ARGB argb XYZW xyzw -> AAAA aaaa XXXX xxxx
 
+    // Mask away color or alpha lanes.
+    Sk4px zeroColors() const;  // ARGB argb XYZW xyzw -> A000 a000 X000 x000
+    Sk4px zeroAlphas() const;  // ARGB argb XYZW xyzw -> 0RGB 0rgb 0YZW 0yzw
+
     Sk4px inv() const { return Sk16b(255) - *this; }
 
     // When loading or storing fewer than 4 SkPMColors, we use the low lanes.
     static Sk4px Load4(const SkPMColor[4]);  // PMColor[4] -> ARGB argb XYZW xyzw
     static Sk4px Load2(const SkPMColor[2]);  // PMColor[2] -> ARGB argb ???? ????
     static Sk4px Load1(const SkPMColor[1]);  // PMColor[1] -> ARGB ???? ???? ????
 
     // Ditto for Alphas... Load2Alphas fills the low two lanes of Sk4px.
     static Sk4px Load4Alphas(const SkAlpha[4]);  // AaXx -> AAAA aaaa XXXX xxxx
     static Sk4px Load2Alphas(const SkAlpha[2]);  // Aa   -> AAAA aaaa ???? ????
@@ skipping 16 matching lines @@
             return Sk4px::Wide(*this + Sk16h(128)).div255TruncNarrow();
         }
 
     private:
         typedef Sk16h INHERITED;
     };
 
     Wide widenLo() const;               // ARGB -> 0A 0R 0G 0B
     Wide widenHi() const;               // ARGB -> A0 R0 G0 B0
     Wide mulWiden(const Sk16b&) const;  // 8-bit x 8-bit -> 16-bit components.
+    Wide mul255Widen() const {
+        // TODO: x*255 = x*256-x, so something like this->widenHi() - this->widenLo()?
+        return this->mulWiden(Sk16b(255));
+    }
 
     // A generic driver that maps fn over a src array into a dst array.
     // fn should take an Sk4px (4 src pixels) and return an Sk4px (4 dst pixels).
     template <typename Fn>
     static void MapSrc(int count, SkPMColor* dst, const SkPMColor* src, Fn fn) {
         // This looks a bit odd, but it helps loop-invariant hoisting across different calls to fn.
         // Basically, we need to make sure we keep things inside a single loop.
         while (count > 0) {
             if (count >= 8) {
                 Sk4px dst0 = fn(Load4(src+0)),
@@ skipping 91 matching lines @@
     #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
         #include "../opts/Sk4px_SSE2.h"
     #elif defined(SK_ARM_HAS_NEON)
         #include "../opts/Sk4px_NEON.h"
     #else
         #include "../opts/Sk4px_none.h"
     #endif
 #endif
 
 #endif//Sk4px_DEFINED