Transparency is wrong

[Beosar]

Hi,

I have created a semi-transparent glass "texture" (see attached image) in Gimp 2.10 which is just a single color. I filled the layer mask with 34 (dark grey) and applied it but Gimp outputs the alpha value as 4.

I have opened the image in Photos (the Windows app), which has a background color of #222222. If I put another layer behind the glass texture in Gimp, fill it with #222222 and merge the layers, I get (45, 48, 48). In Photos, the color is (36, 37, 37) and Adobe Photoshop gives me (37, 37, 37).

What is going on?

[Ofnuts]

Are you using high precision in Gimp? (Image > Precision)

[Beosar]

(04-14-2022, 05:18 AM)Ofnuts Wrote: Are you using high precision in Gimp? (Image > Precision)

No, but that was not the problem. It appears GIMP is using linear RGB for alpha blending (unless you're using Legacy mode), which is the correct way to do it. Photos is doing it wrong and there probably is an option in Photoshop for this. I found the answer on StackExchange after a lot of searching.