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July 4, 2022 19:45
Should simplify working with the BLEND_PREMULTIPLIED blend mode.
Starbuck5
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Jul 10, 2022
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I added a bit more information to the documentation. I have a task to make a larger tutorial on pre-multiplied alpha as well to try and explain how to use it with some worked examples. |
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If you call premul-alpha on a surface twice, will the first second result be different from the first? |
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Yes, the output surface will be different because you will multiply by the
alpha again.
I considered flagging a surface after alpha multiplying, but since we can't
do that for loaded surfaces, or constructed in pygame by the user surfaces
(there is no difference between a surface with the intent that it is alpha
multiplied and an identical one where this isn't intended), it seemed like
it would just make it more confusing.
Alpha premultiplication is essentially all about the users blitting intent
rather than something inherent to the pixels.
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If you call premul-alpha on a surface twice, will the first second result
be different from the first?
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Maybe add this to the docs? |
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I can do. |
added 6 commits
July 18, 2022 19:32
# Conflicts: # src_c/simd_blitters.h
# Conflicts: # src_c/alphablit.c # src_c/simd_blitters_sse2.c # src_c/surface.h
Starbuck5
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Nov 7, 2022
Starbuck5
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Nov 7, 2022
Starbuck5
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Nov 7, 2022
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Left a couple minor things to do before merge, but otherwise I couldn't find anything wrong in the PR. Nice job!
JoKing-1999
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Dec 11, 2022
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This should simplify working with the BLEND_PREMULTIPLIED blend mode.
This is an adaption and simplification of an old PR I had lying around. If I get some time before the 2.1.4 release, I will add an AVX2 version of the pre-multiplication - though it's not critical as this shouldn't normally be a critical path function like blit.
I also now kind of want to work up a little BEFORE and AFTER demo program showing how to use the same assets in the old school (normal alpha blending, blits()) way versus the new-ish (premul_alpha(), BLEND_PREMULTIPLED, ublits() - maybe threaded blitting?) way.