Classic Shell: Forum

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.

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.

thank

I found a free program later, that can switch between premultiplied and not premultiplied.
It is called Blender.

I never got around to trying the buttons I converted on an actual menu.
I had just used screenshots.

Here is example of the shutdown button that got set correctly for CSM:

; Shutdown button

Shutdown_selection=19
Shutdown_jump_selection=19
Shutdown_search_selection=19
Shutdown_selection_slices_X=5,14,4,3,14,5
Shutdown_selection_slices_Y=5,14,5

You can be the first to try it.

More about Premultiplied/Straight

Blender software is ok to convert either Straight or premultiplied image.
Just takes a bit of work.
Today I found thoriumknight from 2011:

https://thoriumknight.deviantart.com/ar ... -262526394

has a great software converter, that is very easy to use.
For all those images in example aero.msstyles
What this means is if you like some button and try and use it in Classic Shell skin, the converted image will look correct brightness.
See how the 2nd column transparent button looks brighter in the below picture. It corrected the RGB layer, so it matches like on real Windows Vista/7 start menu.

I tried it it works.
I just had to force Windows 10 to run the program, as it thought it is harmful.
I checked it with Malwarebytes, and Windows Defender. No threats were found.

It makes the Vista taskbar on Classic Shell better looking
than using the unaltered one from MSstyles