Add ability to extract YUV planes from SkImage

src/gpu/effects/GrYUVEffect.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrYUVEffect_DEFINED
+#define GrYUVEffect_DEFINED
+
+#include "SkImageInfo.h"
+
+class GrFragmentProcessor;
+class GrTexture;
+
+namespace GrYUVEffect {
+    /**
+     * Creates an effect that performs color conversion from YUV to RGB. The input textures are
+     * assumed to be kA8_GrPixelConfig.
+     */
+    const GrFragmentProcessor* CreateYUVToRGB(GrTexture* yTexture, GrTexture* uTexture,
+                                              GrTexture* vTexture, const SkISize sizes[3],
+                                              SkYUVColorSpace colorSpace);
+
+    /**
+     * Creates a processor that performs color conversion from the passed in processor's RGB
+     * channels to Y, U ,and V channels. The output color is (y, u, v, a) where a is the passed in
+     * processor's alpha output.
+     */
+    const GrFragmentProcessor* CreateRGBToYUV(const GrFragmentProcessor*,
+                                              SkYUVColorSpace colorSpace);
+
+    /**
+     * Creates a processor that performs color conversion from the passed in processor's RGB
+     * channels to U and V channels. The output color is (u, v, 0, a) where a is the passed in
+     * processor's alpha output.
+     */
+    const GrFragmentProcessor* CreateRGBToUV(const GrFragmentProcessor*,
+                                             SkYUVColorSpace colorSpace);
+    /**
+     * Creates a processor that performs color conversion from the passed in fragment processors's
+     * RGB channels to Y, U, or V (replicated across all four output color channels). The alpha
+     * output of the passed in fragment processor is ignored.
+     */
+    const GrFragmentProcessor* CreateRGBToY(const GrFragmentProcessor*, SkYUVColorSpace colorSpace);
+    const GrFragmentProcessor* CreateRGBToU(const GrFragmentProcessor*, SkYUVColorSpace colorSpace);
+    const GrFragmentProcessor* CreateRGBToV(const GrFragmentProcessor*, SkYUVColorSpace colorSpace);
+};
+
+#endif