JPEG YUV Decoding

include/core/SkImageDecoder.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageDecoder_DEFINED
 #define SkImageDecoder_DEFINED
 
@@ skipping 28 matching lines @@
         kKTX_Format,
 
         kLastKnownFormat = kKTX_Format,
     };
 
     /** Return the format of image this decoder can decode. If this decoder can decode multiple
         formats, kUnknown_Format will be returned.
     */
     virtual Format getFormat() const;
 
+
+    /**  Returns the sizes of each component of the image
+    */
+    virtual bool getComponentSizes(SkStream* stream, SkISize sizes[3]) {
+        return this->onGetComponentSizes(stream, sizes);
+    }
+
+    /* Assigns buffers for YUV decoding
+    */
+    void setYUVBuffers(void* yuv[3], size_t rowBytes[3]) {
+        this->onSetYUVBuffers(yuv, rowBytes);
+    }
+
     /** Return the format of the SkStreamRewindable or kUnknown_Format if it cannot be determined.
         Rewinds the stream before returning.
     */
     static Format GetStreamFormat(SkStreamRewindable*);
 
     /** Return a readable string of the Format provided.
     */
     static const char* GetFormatName(Format);
 
     /** Return a readable string of the value returned by getFormat().
@@ skipping 318 matching lines @@
     virtual bool onBuildTileIndex(SkStreamRewindable*, int *width, int *height) {
         return false;
     }
 
     // If the decoder wants to support tiled based decoding,
     // this method must be overridden. This guy is called by decodeRegion(...)
     virtual bool onDecodeSubset(SkBitmap* bitmap, const SkIRect& rect) {
         return false;
     }
 
+    /* If the decoder wants to support YUV based decoding, this method must be overridden.
+    */
+    virtual void onSetYUVBuffers(void* yuv[3], size_t rowBytes[3]) {}

[scroggo, 2014/07/25 20:48:34]

Why not create a new entry point? Right now the client makes calls something
like:

  decoder->getComponentSIzes();
  decoder->setYUVBuffers();
  SkBitmap ignoredBitmap;
  decoder->decode(&ignoredBitmap); // Not meaningfully used but cannot be NULL

wouldn't it be cleaner if we had some function like

  SkImageDecoder::decodeIntoYUV();

?

+
+    /**  Returns the sizes of each component of the image
+    */
+    virtual bool onGetComponentSizes(SkStream*, SkISize sizes[3]) {
+        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.
      *
      * @param dst the destination bitmap.
      * @param src the source bitmap that is sampled by sampleSize from the
      *            original bitmap.
      * @param sampleSize the sample size that src is sampled from the original bitmap.
      * @param (dstX, dstY) the upper-left point of the dest bitmap in terms of
      *                     the coordinate in the original bitmap.
@@ skipping 128 matching lines @@
 DECLARE_DECODER_CREATOR(WEBPImageDecoder);
 DECLARE_DECODER_CREATOR(PKMImageDecoder);
 DECLARE_DECODER_CREATOR(KTXImageDecoder);
 
 // Typedefs to make registering decoder and formatter callbacks easier.
 // These have to be defined outside SkImageDecoder. :(
 typedef SkTRegistry<SkImageDecoder*(*)(SkStreamRewindable*)>        SkImageDecoder_DecodeReg;
 typedef SkTRegistry<SkImageDecoder::Format(*)(SkStreamRewindable*)> SkImageDecoder_FormatReg;
 
 #endif