Allowing YUV data to be retrieved from the JPEG Decoder.

Source/platform/image-decoders/ImageDecoder.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 31 matching lines @@
 #if USE(QCMSLIB)
 #include "qcms.h"
 #if OS(MACOSX)
 #include <ApplicationServices/ApplicationServices.h>
 #include "wtf/RetainPtr.h"
 #endif
 #endif
 
 namespace blink {
 
+// DecodingBuffers can be used to decode color components into provided buffers instead of using an ImageFrame.
+class DecodingBuffers {

[Alpha Left Google, 2014/07/24 22:07:27]

This should be called ImagePlanes to be clear.

[sugoi1, 2014/07/24 23:16:35]

Acknowledged.

+public:
+    DecodingBuffers();
+
+    void set(void* planes[3], size_t rowBytes[3]);

[Alpha Left Google, 2014/07/24 22:07:27]

It will not always be 3 planes but it's good for now.

[sugoi1, 2014/07/24 23:16:35]

Acknowledged.

+    void* getPlane(int);

[Noel Gordon, 2014/07/25 15:55:01]

blink webcore convention: no "get" prefix in class getters.

[sugoi1, 2014/07/25 16:56:48]

Done.

+    size_t getRowBytes(int) const;
+
+private:
+    void* m_planes[3];
+    size_t m_rowBytes[3];
+};
+
 // ImageDecoder is a base for all format-specific decoders
 // (e.g. JPEGImageDecoder). This base manages the ImageFrame cache.
 //
 class PLATFORM_EXPORT ImageDecoder {
     WTF_MAKE_NONCOPYABLE(ImageDecoder); WTF_MAKE_FAST_ALLOCATED;
 public:
     static const size_t noDecodedImageByteLimit = blink::Platform::noDecodedImageByteLimit;
 
     ImageDecoder(ImageSource::AlphaOption alphaOption, ImageSource::GammaAndColorProfileOption gammaAndColorProfileOption, size_t maxDecodedBytes)
         : m_premultiplyAlpha(alphaOption == ImageSource::AlphaPremultiplied)
@@ skipping 31 matching lines @@
     // decode call out and use it here.
     virtual bool isSizeAvailable()
     {
         return !m_failed && m_sizeAvailable;
     }
 
     virtual IntSize size() const { return m_size; }
 
     // Decoders which downsample images should override this method to
     // return the actual decoded size.
-    virtual IntSize decodedSize() const { return size(); }
+    virtual IntSize decodedSize(int component = 0) const { return size(); }

[Noel Gordon, 2014/07/25 15:55:01]

I believe the Androids might downsample when decoding images.  Did you check if
yuv decoding interworks with that?

[sugoi1, 2014/07/25 16:56:48]

Looking at DecodingImageGenerator::onGetPixels() :
"Implementation doesn't support scaling yet so make sure we're not given a
different size."

For now, I could bail out if any scaling factor is given since it's not yet
supported. I can add that functionality as a follow up.

 
     // This will only differ from size() for ICO (where each frame is a
     // different icon) or other formats where different frames are different
     // sizes. This does NOT differ from size() for GIF or WebP, since
     // decoding GIF or WebP composites any smaller frames against previous
     // frames to create full-size frames.
     virtual IntSize frameSizeAtIndex(size_t) const
     {
         return size();
     }
@@ skipping 130 matching lines @@
     virtual void setMemoryAllocator(SkBitmap::Allocator* allocator)
     {
         // FIXME: this doesn't work for images with multiple frames.
         if (m_frameBufferCache.isEmpty()) {
             m_frameBufferCache.resize(1);
             m_frameBufferCache[0].setRequiredPreviousFrameIndex(
                 findRequiredPreviousFrame(0, false));
         }
         m_frameBufferCache[0].setMemoryAllocator(allocator);
     }
 

[Alpha Left Google, 2014/07/24 22:07:26]

How do I know if the code that uses this decoder can draw the YUV subsampled
data? I think it's good to have method to query YUV subsampling.

[sugoi1, 2014/07/24 23:16:35]

I'm not sure I understand your question. The code would only call these methods
if it wants the YUV data, no? There shouldn't be any surprises for the code
calling these.

[Alpha Left Google, 2014/07/24 23:30:56]

I mean there's different types of subsampling. My question is if the caller
enables YUV decoding, it must handle all subsampling types. Is it true?

[sugoi1, 2014/07/25 02:55:13]

Well, the caller first receives the size of the Y, U and V planes and could
choose to support it or not based on the sizes received. It's fairly easy to
deduce the subsampling type from the sizes.

But, yes, currently the caller can handle all subsampling types. Note that the
JPEG decoder will only accept to set the output type to YUV if the subsampling
is one of : 4:4:4, 4:4:0, 4:2:2, 4:2:0, 4:1:1, 4:1:0, so only 6 subsampling
types need to be supported currently.

+    virtual void setAcceleratedYUVDecoding(bool) { }

[Alpha Left Google, 2014/07/24 22:07:26]

nit: drop "accelerated" from methods names. Decoding is still in software so
nothing is accelerated from the point of view of decoders.

[sugoi1, 2014/07/24 23:16:35]

Acknowledged.

+    virtual bool acceleratedYUVDecoding() const { return false; }
+    virtual bool doAcceleratedYUVDecoding() { return false; }
+    virtual void setDecodingBuffers(OwnPtr<DecodingBuffers>&) { }
+
 protected:
     // Calculates the most recent frame whose image data may be needed in
     // order to decode frame |frameIndex|, based on frame disposal methods
     // and |frameRectIsOpaque|, where |frameRectIsOpaque| signifies whether
     // the rectangle of frame at |frameIndex| is known to be opaque.
     // If no previous frame's data is required, returns WTF::kNotFound.
     //
     // This function requires that the previous frame's
     // |m_requiredPreviousFrameIndex| member has been set correctly. The
     // easiest way to ensure this is for subclasses to call this method and
@@ skipping 34 matching lines @@
 
     IntSize m_size;
     bool m_sizeAvailable;
     bool m_isAllDataReceived;
     bool m_failed;
 };
 
 } // namespace blink
 
 #endif