experiment: float color components

src/core/SkColor.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 "SkColor.h"
 #include "SkColorPriv.h"
 #include "SkFixed.h"
@@ skipping 82 matching lines @@
     switch (hx >> 16) {
         case 0: r = v; g = t; b = p; break;
         case 1: r = q; g = v; b = p; break;
         case 2: r = p; g = v; b = t; break;
         case 3: r = p; g = q; b = v; break;
         case 4: r = t;  g = p; b = v; break;
         default: r = v; g = p; b = q; break;
     }
     return SkColorSetARGB(a, r, g, b);
 }
+
+#include "SkMathPriv.h"
+
+SkColor4f SkColor4f::Normalize(float a, float r, float g, float b) {

[mtklein, 2016/01/21 19:28:30]

Pin?  (Also, SkNx this?)

+    return { SkPinToUnitFloat(a), SkPinToUnitFloat(r), SkPinToUnitFloat(g), SkPinToUnitFloat(b) };
+}
+
+SkColor4f SkColor4f::FromColor(SkColor c) {

[mtklein, 2016/01/21 19:28:30]

Something like,

#include "SkNx.h"
 SkColor4f SkColor4f::FromColor(SkColor c) {
     auto f4 = SkNx_cast<float>(Sk4b::Load((const uint8_t*)&c));

     // b,g,r,a -> a,r,g,b
     f4 = SkNx_shuffle<3,2,1,0>(f4);
     f4 = f4 * Sk4f(1.0f/255);

     SkColor4f r;
     f4.store(&r.fA);
     return r;
 }

+    const float kOneOver255 = 1.0f / 255;
+    return {
+        SkColorGetA(c) * kOneOver255, SkColorGetR(c) * kOneOver255,
+        SkColorGetG(c) * kOneOver255, SkColorGetB(c) * kOneOver255
+    };
+}
+
+SkPM4f SkColor4f::premul() const {
+    SkColor4f src = this->normalize();
+    SkPM4f dst;
+    dst.fVec[SK_A32_SHIFT/8] = src.fA;
+    dst.fVec[SK_R32_SHIFT/8] = src.fR;
+    dst.fVec[SK_G32_SHIFT/8] = src.fG;
+    dst.fVec[SK_B32_SHIFT/8] = src.fB;
+    return dst;
+}