Generic 4f gradient T sampler fallback

src/effects/gradients/Sk4fGradientPriv.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef Sk4fGradientPriv_DEFINED
+#define Sk4fGradientPriv_DEFINED
+
+#include "SkColor.h"
+#include "SkNx.h"
+#include "SkPM4f.h"
+
+// Templates shared by various 4f gradient flavors.
+
+namespace {
+
+inline Sk4f premul_4f(const Sk4f& c) {
+    const float alpha = c[SkPM4f::A];
+    // FIXME: portable swizzle?
+    return c * Sk4f(alpha, alpha, alpha, 1);
+}
+
+template <bool do_premul>
+inline SkPMColor trunc_from_255(const Sk4f& c) {
+    SkPMColor pmc;
+    SkNx_cast<uint8_t>(c).store(&pmc);
+    if (do_premul) {
+        pmc = SkPreMultiplyARGB(SkGetPackedA32(pmc), SkGetPackedR32(pmc),
+                                SkGetPackedG32(pmc), SkGetPackedB32(pmc));
+    }
+    return pmc;
+}
+
+template<typename DstType, bool do_premul>
+void store(const Sk4f& color, DstType* dst);
+
+template<>
+inline void store<SkPM4f, false>(const Sk4f& c, SkPM4f* dst) {
+    c.store(dst);
+}
+
+template<>
+inline void store<SkPM4f, true>(const Sk4f& c, SkPM4f* dst) {
+    store<SkPM4f, false>(premul_4f(c), dst);
+}
+
+template<>
+inline void store<SkPMColor, false>(const Sk4f& c, SkPMColor* dst) {
+    *dst = trunc_from_255<false>(c);
+}
+
+template<>
+inline void store<SkPMColor, true>(const Sk4f& c, SkPMColor* dst) {
+    *dst = trunc_from_255<true>(c);
+}
+
+template<typename DstType, bool do_premul>
+inline void store4x(const Sk4f& c0,
+                    const Sk4f& c1,
+                    const Sk4f& c2,
+                    const Sk4f& c3,
+                    DstType* dst) {
+    store<DstType, do_premul>(c0, dst++);
+    store<DstType, do_premul>(c1, dst++);
+    store<DstType, do_premul>(c2, dst++);
+    store<DstType, do_premul>(c3, dst++);
+}
+
+template<>
+inline void store4x<SkPMColor, false>(const Sk4f& c0,
+                                      const Sk4f& c1,
+                                      const Sk4f& c2,
+                                      const Sk4f& c3,
+                                      SkPMColor* dst) {
+    Sk4f_ToBytes((uint8_t*)dst, c0, c1, c2, c3);
+}
+
+template<typename DstType>
+float dst_component_scale();
+
+template<>
+inline float dst_component_scale<SkPM4f>() {
+    return 1;
+}
+
+template<>
+inline float dst_component_scale<SkPMColor>() {
+    return 255;
+}
+
+template<typename DstType>
+Sk4f dst_swizzle(const SkPM4f&);
+
+template<>
+inline Sk4f dst_swizzle<SkPM4f>(const SkPM4f& c) {
+    return c.to4f();
+}
+
+template<>
+inline Sk4f dst_swizzle<SkPMColor>(const SkPM4f& c) {
+    return c.to4f_pmorder();
+}
+
+}
+
+#endif // Sk4fGradientPriv_DEFINED