Bug with low opacity layer on transparent background?

[Tsuchimi22]

My god finally!

The 'Composite Space' keyword on Google gives me a lot of result about it and my problem.
Thank you for the explanation video, I'll try to get further into this because it seems totally counter-intuitive to me. I understand the problem but can't get why it's now "by default" yet because the resolution of this blurring problem seems to bring more issues than it supposes to solve. But I may be wrong.

Anyway, thank you very much! 

[rich2005]

A  search for a good explanation of why linear mode affects transparency like that - nothing so far. There are users who complain that the Gimp 2.10 GEGL gaussian blur is too different from the Gimp 2.8 blur.

Using Gimp 2.10 there is another way to apply that effect, the new drop shadow filter.

   

[PixLab]

(04-17-2022, 10:19 AM)Tsuchimi22 Wrote: Thank you for your answers but.. I think there is a misunderstanding somewhere because we don't talk about the same thing.
What you describe and solutions you offer is not what I'm concern.

PixLab Wrote:This behavior did not change with GIMP 2.10

It did. There is a different philosophy of handling layer opacity between versions. I don't know if it's better or not, but what is certain is that it changes somehow.
I'll try to explain better. I redownload Gimp 2.8 to make the comparison.

Gimp 2.8



Here we have our 3 layers. In the middle, it's the famous "low opacity layer" at 60%.
On Gimp 2.8, whatever the state of the black background layer (visible or not), the render will be THE SAME on a dark background after I put it somewhere in PNG. I'm web developper (but not designer no kiding), so suppose it's a website where the background-color is black.

To be more precise of my work habits : to create some little logos, images with a little bit a stylization of this kind, I use to work on black background (because global graphics of my website tend towards grey/black). But when I finish, I delete the black background so it lefts transparent and I export it in PNG. But, I know that if I re-place it in on some black background (or not that's the point, I start from 100% black but in the final it could be a black gradient background, a white / black photo...), it will have the same result as I used to work on the software.

Gimp 2.10



This time, the same thing but with Gimp 2.10.
What bothers me and confuses me is this time, the render will DEPENDS ON the state of the black background layer (visible or not). Again, consider the final of the final is to put it in some black background on website. So here I'm totally wrong. I work with black background supposing it'll have the same aspect on black background when I'll export it in transparent. But it won't.

One important thing I notice when doing this comparison is this time : my layer in the middle need to be at 16% to match the aspect of the Gimp 2.8 version.
And I think the key is probably here ?

if I haven't gone completely crazy yet, we can clearly see a difference of behavior of the opacity tool in the final result between theses two versions of Gimp.
And I'd like to understand it properly to retrieve my habits or to change it if I have to change it.

Ok, now I understand what you're speaking about
I'm glad you also got a solution.