refactor parts of SkGr.cpp for use by SkImages

src/gpu/GrYUVProvider.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrYUVProvider_DEFINED
+#define GrYUVProvider_DEFINED
+
+#include "GrTypes.h"
+#include "SkImageInfo.h"
+
+class GrContext;
+class GrTexture;
+
+/**
+ *  There are at least 2 different ways to extract/retrieve YUV planar data...
+ *  - SkPixelRef
+ *  - SkImageGeneartor
+ *
+ *  To share common functionality around using the planar data, we use this abstract base-class
+ *  to represent accessing that data.
+ */
+class GrYUVProvider {
+public:
+    virtual ~GrYUVProvider() {}
+
+    /**
+     *  On success, this returns a texture that has converted the YUV data from the provider
+     *  into a form that is supported by the GPU (typically transformed into RGB). If useCache
+     *  is true, then the texture will automatically have a key added, so it can be retrieved
+     *  from the cache (assuming it is requested by a provider w/ the same genID).
+     *
+     *  On failure (e.g. the provider had no data), this returns NULL.
+     */
+    GrTexture* refAsTexture(GrContext*, const GrSurfaceDesc&, bool useCache);
+
+    virtual uint32_t onGetID() = 0;
+
+    enum {
+        kY_Index = 0,
+        kU_Index = 1,
+        kV_Index = 2,
+
+        kPlaneCount = 3
+    };
+
+    // These are not meant to be called by a client, only by the implementation
+
+    /**
+     *  Return the 3 dimensions for each plane and return true. On failure, return false and
+     *  ignore the sizes parameter. Typical failure is that the provider does not contain YUV
+     *  data, and may just be an RGB src.
+     */
+    virtual bool onGetYUVSizes(SkISize sizes[kPlaneCount]) = 0;
+
+    /**
+     *  On success, return true, and set sizes, rowbytes and colorspace to the appropriate values.
+     *  planes[] will have already been allocated by the client (based on the worst-case sizes
+     *  returned by onGetYUVSizes(). This method copies its planar data into those buffers.
+     *
+     *  On failure, return false and ignore other parameters.
+     */
+    virtual bool onGetYUVPlanes(SkISize sizes[kPlaneCount], void* planes[kPlaneCount],
+                                size_t rowBytes[kPlaneCount], SkYUVColorSpace*) = 0;
+};
+
+#endif