Gaussian blur in Mac OS GIMP does not correctly blur the alpha channel
Environment/Versions
- GIMP version: 2.10.36
- Package: Installer from gimp.org, also in MacPorts build
- Operating System: Mac OS Sonoma 14.3.1
Description of the bug
Applying Gaussian Blur on a layer that has an Alpha channel, will not fully blur the alpha channel. The original un-blurred channel seems to be overlaid onto the blurred result.
Reproduction
Is the bug reproducible? Always
Reproduction steps:
- Open attached BlurTest.xcf file.BlurTest.xcf
- Apply Gaussian Blur with radius 8 or greater.
- Observe result.
Expected result:
The black and white regions are fully blurred. This is the result I get with GIMP 2.10.36 in Ubuntu installed through snap.
Actual result:
The result I get in the Mac OS build, looks like the un-blurred image overlaid onto the blurred image. The 1-pixel wide details can still be discerned, which should be impossible with an 8-pixel radius blur.
Additional information
I don't seem to remember seeing this problem while I was using GIMP in Mac OS Ventura. I have tried reinstalling my entire MacPorts including GIMP, but the bug is still present. The other types of blur filters seem to work as expected.