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PostPosted: Thu Jan 05, 2017 1:46 pm 
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Joined: Thu Jun 13, 2013 12:07 pm
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Premultiplied Alpha and not premultiplied images.


From what I see in the skinning tutorial, CSM does not use premultiplied images:
"For 32-bit images don't premultiply the alpha channel. If you don't know what "premultiply the alpha" means, never mind."


A lot of buttons, user picture frames, menu images from msstyles files have some type of premultiplied alpha in them.
It's some kind of merging, and throwing away pixels process. They appear darker in a photo program.

Example red color:

* Red pixels with a premultiplied alpha of 50% have 8bit RGBA value: 127,0,0,127

* Red pixels with a ………straight alpha of 50% have 8bit RGBA value: 255,0,0,127

What's puzzling to me is photo programs do this anyway, and a premultiplied, or not premultipled same image look same in editor.
I think MS multiplied with a different factor, to make it hard on us. :x

How to exactly undo premultiplied alpha image, so it can be used?
Beats the H%LL out of me, and everyone else.
Can only boost the brightness of all channels to get approximate look from original os.


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Not premultiplied. examples.zip [1.15 KiB]
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