experiment: float color components

src/core/SkColor.cpp

Index: src/core/SkColor.cpp
diff --git a/src/core/SkColor.cpp b/src/core/SkColor.cpp
index a21f0192398f95ba3c4256a41c0d2ff47da4ed64..a80a78597a83fd7e701aad89c3aff39cdf2434c9 100644
--- a/src/core/SkColor.cpp
+++ b/src/core/SkColor.cpp
@@ -100,3 +100,27 @@ SkColor SkHSVToColor(U8CPU a, const SkScalar hsv[3]) {
     }
     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;
+}