What would be great is to be able to "render" transparent pixels... Sort of premultiplied alpha, but not during the saving picture process (it already exists when PNG is used for ex.),
but the Photoshop-way :
That is why the Photoshop-like transparent background is needed, i can't use any arbitrary background except a 128grey as a medium-range one...
the 'Photoshop-like transparent bg needed' is only a visual interpretation of a black alpha channel. That's all.
asking for transparent pixel rendering shows a misconception of the premultiply thing.
https://limnu.com/premultiplied-alpha-primer-artists/I only had a brief look into it, but it seems ok.
I had a very hard and long time myself fully understanding the concept of premultiplied/unpremultiplied. But after I got it I never complained about 'fringes' or 'contours'.
Key is to know what you've got: Pre or unpremultiplied images.
When you will need to know what the software getting the images expect to get: Pre or unpremultiplied images.
And if this mismatches you'll either have to to tell the software otherwise or use a premultiply/unpremultiply operation.
Hope this helps a bit...