[Bf-codereview] Alpha premul pipeline cleanup (issue 7018048)

[brechtvanlommel at gmail.com]

https://codereview.appspot.com/7018048/diff/1/intern/opencolorio/fallback_impl.cc
File intern/opencolorio/fallback_impl.cc (right):

https://codereview.appspot.com/7018048/diff/1/intern/opencolorio/fallback_impl.cc#newcode266
intern/opencolorio/fallback_impl.cc:266: inv_alpha = alpha != 0.0f ?
1.0f / alpha : 1.0f;
This test is unnecessary given that it already checks for pixel[3] ==
0.0f above.

https://codereview.appspot.com/7018048/diff/1/intern/opencolorio/ocio_impl.cc
File intern/opencolorio/ocio_impl.cc (right):

https://codereview.appspot.com/7018048/diff/1/intern/opencolorio/ocio_impl.cc#newcode408
intern/opencolorio/ocio_impl.cc:408: inv_alpha = alpha != 0.0f ? 1.0f /
alpha : 1.0f;
Same here

https://codereview.appspot.com/7018048/diff/1/source/blender/makesrna/intern/rna_scene.c
File source/blender/makesrna/intern/rna_scene.c (left):

https://codereview.appspot.com/7018048/diff/1/source/blender/makesrna/intern/rna_scene.c#oldcode3336
source/blender/makesrna/intern/rna_scene.c:3336: -		{R_ALPHAKEY,
"STRAIGHT", 0, "Straight Alpha", "Transparent RGB and alpha pixels are
unmodified"},
I think this option could become "Sky" and "Transparent". In the tooltip
for transparent it can perhaps mentioned that the alpha is
premultiplied.

https://codereview.appspot.com/7018048/diff/1/source/blender/makesrna/intern/rna_sequencer.c
File source/blender/makesrna/intern/rna_sequencer.c (right):

https://codereview.appspot.com/7018048/diff/1/source/blender/makesrna/intern/rna_sequencer.c#newcode1545
source/blender/makesrna/intern/rna_sequencer.c:1545:
{SEQ_ALPHA_STRAIGHT, "STRAIGHT", 0, "Straight", "Transparent RGB and
alpha pixels are unmodified"},
Suggestions to make the description more clear:
RGB channels in transparent pixels are unaffected by the alpha channel

https://codereview.appspot.com/7018048/diff/1/source/blender/makesrna/intern/rna_sequencer.c#newcode1546
source/blender/makesrna/intern/rna_sequencer.c:1546: {SEQ_ALPHA_PREMUL,
"PREMUL", 0, "Premultiplied", "Transparent RGB pixels are multiplied by
the alpha channel"},
RGB channels in transparent pixels are multiplied by the alpha channel

https://codereview.appspot.com/7018048/