Add SkGammaColorFilter

src/effects/SkGammaColorFilter.cpp

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkGammaColorFilter.h"
+
+#include "SkReadBuffer.h"
+#include "SkString.h"
+
+#if SK_SUPPORT_GPU
+#include "effects/GrGammaEffect.h"
+#endif
+
+void SkGammaColorFilter::filterSpan(const SkPMColor src[], int count,
+                                    SkPMColor dst[]) const {
+    // Gamma-correcting bytes to bytes is pretty questionable.
+    SkASSERT(0);
+    for (int i = 0; i < count; ++i) {
+        SkPMColor c = src[i];
+
+        // TODO: implement cpu gamma correction?
+        dst[i] = c;
+    }
+}
+
+sk_sp<SkColorFilter> SkGammaColorFilter::Make(SkScalar gamma) {
+    return sk_sp<SkColorFilter>(new SkGammaColorFilter(gamma));
+}
+
+SkGammaColorFilter::SkGammaColorFilter(SkScalar gamma) : fGamma(gamma) {}
+
+sk_sp<SkFlattenable> SkGammaColorFilter::CreateProc(SkReadBuffer& buffer) {
+    SkScalar gamma = buffer.readScalar();
+
+    return Make(gamma);
+}
+
+void SkGammaColorFilter::flatten(SkWriteBuffer& buffer) const {
+    this->INHERITED::flatten(buffer);
+    buffer.writeScalar(fGamma);
+}
+
+#ifndef SK_IGNORE_TO_STRING
+void SkGammaColorFilter::toString(SkString* str) const {
+    str->appendf("SkGammaColorFilter (%.2f)", fGamma);
+}
+#endif
+
+#if SK_SUPPORT_GPU
+sk_sp<GrFragmentProcessor> SkGammaColorFilter::asFragmentProcessor(GrContext*) const {
+    return GrGammaEffect::Make(fGamma);
+}
+#endif