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..c9f4a1433dfd9a856c5d7f6bed4725147e0bde89 100644
--- a/src/core/SkColor.cpp
+++ b/src/core/SkColor.cpp
@@ -100,3 +100,37 @@ SkColor SkHSVToColor(U8CPU a, const SkScalar hsv[3]) {
     }
     return SkColorSetARGB(a, r, g, b);
 }
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+#include "SkNx.h"
+
+SkColor4f SkColor4f::Pin(float a, float r, float g, float b) {
+    SkColor4f c4;
+    Sk4f::Min(Sk4f::Max(Sk4f(a, r, g, b), Sk4f(0)), Sk4f(1)).store(c4.vec());
+    return c4;
+}
+
+SkColor4f SkColor4f::FromColor(SkColor c) {
+    Sk4f value = SkNx_shuffle<3,2,1,0>(SkNx_cast<float>(Sk4b::Load((const uint8_t*)&c)));
+    SkColor4f c4;
+    (value * Sk4f(1.0f / 255)).store(c4.vec());
+    return c4;
+}
+
+SkPM4f SkColor4f::premul() const {
+    auto src = Sk4f::Load(this->pin().vec());
+    float srcAlpha = src.kth<0>();  // need the pinned version of our alpha
+    src = src * Sk4f(1, srcAlpha, srcAlpha, srcAlpha);
+
+#ifdef SK_PMCOLOR_IS_BGRA
+    // ARGB -> BGRA
+    Sk4f dst = SkNx_shuffle<3,2,1,0>(src);
+#else
+    // ARGB -> RGBA
+    Sk4f dst = SkNx_shuffle<1,2,3,0>(src);
+#endif
+
+    SkPM4f pm4;
+    dst.store(pm4.fVec);
+    return pm4;
+}