Add 4:2:0 YUVA to ARGB & ABGR conversion for SkCanvasVideoRenderer.

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For this function:
https://code.google.com/p/chromium/codesearch#chromium/src/media/blink/skcanvas_
video_renderer.cc&l=581

Could just do YV12 -> ARGB/ABGR and copy and attenuate alpha.

Original issue reported on code.google.com by dalecurtis@chromium.org on 24 Jul 2015 at 9:47

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There's an SkCanvasVideoRenderer unittest in media_blink_unittests

Original comment by dalecurtis@chromium.org on 24 Jul 2015 at 10:00

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Theres 3 ways to implement this:

1. Caller can do 2 steps: I420ToARGB and ARGBCopyYToAlpha   

ARGBCopyYToAlpha takes a plane of data and copies it to the 4th byte of ARGB.  
See planarfunctions.h
LIBYUV_API
int ARGBCopyYToAlpha(const uint8* src_y, int src_stride_y,
                     uint8* dst_argb, int dst_stride_argb,
                     int width, int height);

Advantages:
a. Allows any form of I420 conversion, including I422, J420 and ABGR 
destination.  b. works with existing libyuv.
c. both functions are highly optimized including AVX2.
Disadvantage:
a. less cache/memory friendly for large images where ARGB destination doesnt 
fit cache.

2. Implement A420ToARGB (I420 with alpha), internally doing 2 steps per row.
Advantages:
a. faster - using a row buffer for intermediate ARGB is cache friendly.
b. abstracts implementation, which can be improved in future.
Disadvantage:
a. implements a specific color space.  less flexible.

3. Implement optimized A420ToARGB.
Internally the I420ToARGB is done with 3 macros to implement the I420 fetch, 
YUV conversion, and ARGB storing.  The ARGB storing fills in 255.  This macro 
could implement a variation that fetches alpha from another pointer.
Advantage: fastest
Disadvantage: most complex, least flexible.

Original comment by fbarch...@chromium.org on 11 Aug 2015 at 6:03

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I420AlphaToARGB implemented in r1466

I420AlphaToARGB_Any (1373 ms)
I420AlphaToARGB_Unaligned (1625 ms)
I420AlphaToARGB_Invert (1303 ms)
I420AlphaToARGB_Opt (1302 ms)

I420ToARGB_Any (660 ms)
I420ToARGB_Unaligned (637 ms)
I420ToARGB_Invert (615 ms)
I420ToARGB_Opt (542 ms)

Original comment by fbarch...@chromium.org on 18 Aug 2015 at 6:25

• Changed state: Started

[GoogleCodeExporter]

change is integrated into chrome.

a followup improvement would be I420AlphaToABGR and some performance 
improvements.

Original comment by fbarch...@chromium.org on 20 Aug 2015 at 11:32

• Changed state: Fixed

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This is the CL that switches to libyuv::I420AlphaToARGB
https://codereview.chromium.org/1293293003/

Original comment by fbarch...@chromium.org on 21 Aug 2015 at 12:49

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Starting ABGR version.

Original comment by fbarch...@chromium.org on 21 Aug 2015 at 1:07

• Changed state: Started

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Performance went from 2 steps (for android)
SkCanvasVideoRendererTest.TransparentFrame (1610 ms)
to 1 step:
SkCanvasVideoRendererTest.TransparentFrame (1256 ms)

Original comment by fbarch...@chromium.org on 27 Aug 2015 at 1:25

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ABGR integrated into skcanvas.

consider merging ARGB and ABGR functions into a single function and exposing 
other color spaces - BGRA, J420 etc.

consider removing premultiplication and have renderer do unattenuated alpha 
blend.

consider implmenting I420AlphaToARGB internally as a single assembly function, 
which fills in alpha as it goes, instead of filling in 255 and then doing 2nd 
step to copy, and/or third step to attenuate RGB by alpha.

Original comment by fbarch...@chromium.org on 27 Aug 2015 at 1:40

• Changed state: Fixed