JPEG YUV Decoding

include/core/SkImageDecoder.h

Index: include/core/SkImageDecoder.h
diff --git a/include/core/SkImageDecoder.h b/include/core/SkImageDecoder.h
index 5910d33a997a4950aad0694d1beb0619f6edb31b..1c975063eae0b28ee75fb25b81b6d318d9da74c8 100644
--- a/include/core/SkImageDecoder.h
+++ b/include/core/SkImageDecoder.h
@@ -18,6 +18,24 @@
 class SkStream;
 class SkStreamRewindable;
 
+/** \class SkImagePlanes
+
+    SkImagePlanes can be used to decode color components into provided buffers
+    instead of using an SkBitmap.
+*/
+class SkImagePlanes : public SkRefCnt {
+public:
+    SkImagePlanes();
+    SkImagePlanes(void* planes[3], size_t rowBytes[3]);
+
+    void* plane(int);
+    size_t rowBytes(int) const;
+
+private:
+    void* m_planes[3];
+    size_t m_rowBytes[3];
+};
+
 /** \class SkImageDecoder
 
     Base class for decoding compressed images into a SkBitmap
@@ -47,6 +65,17 @@ public:
     */
     virtual Format getFormat() const;
 
+    /** Returns the sizes of each component of the image
+        @param sizes On success, returns the sizes of each component of the image.
+    */
+    bool getYUVComponentSizes(SkStream* stream, SkISize sizes[3]);
+
+    /** Decodes the YUV planes into the provided planes
+        Returns whether the decoding to YUV was successful.
+    */
+    bool decodeToYUV(SkStream* stream, SkISize componentSizes[3], void* planes[3],
+                     size_t rowBytes[3]);
+
     /** Return the format of the SkStreamRewindable or kUnknown_Format if it cannot be determined.
         Rewinds the stream before returning.
     */
@@ -339,6 +368,17 @@ protected:
         return false;
     }
 
+    /** If imagePlanes is NULL, decodes the header and computes componentSizes
+        for memory allocation.
+        Otherwise, decodes the YUV planes into the provided image planes and
+        updates componentSizes to the final image size.
+        Returns whether the decoding was successful.
+    */
+    virtual bool onDecodeToYUV(SkStream* stream, SkISize componentSizes[3],
+                               SkImagePlanes* imagePlanes) {

[reed1, 2014/10/13 13:15:35]

I thnk passing the planes and sizes arrays is better than creating s small
object to hold them. i.e. not sure we need SkImagePlanes object.

[sugoi1, 2014/10/14 15:07:36]

Done. This was added only to mimic what is used in Blink, but since skia's
decoder is much simpler, it's not required.

+        return false;
+    }
+
     /*
      * Crop a rectangle from the src Bitmap to the dest Bitmap. src and dst are
      * both sampled by sampleSize from an original Bitmap.