Filter Inverse Diffusion bug

I use Sharpen [inverse diffusion] all the time and have noticed weird artifacts depending on the particular image, but this is new. From 0px to 262px in the X plane, it has overblown the sharpening of the lines and then abruptly stops. The rest of the image is sharpened as intended.

Here’s the image before sharpening.

My Settings

and result

I’m not sure if it’s related, but the " reset parameters to default values" does not work on this filter.

Thanks.

P.S. Is there a way to have the Before and After preview be vertical instead of horizontal?

@akovia Welcome to the forum!

I can confirm your issue (GIMP 2.10.18 + G’MIC 2.9.0). The odd thing is that preview sometimes doesn’t show this error, but it always shows up when applied.

The workaround is to rectangle select the character side of the image. Then, all you need to do is to clone the pattern to the left. Apparently, if I select a smaller length of the horizontal lines, this artifact doesn’t occur.

In general, I would advise against sharpening the background, as sharpening would generate undesirable halos along the lines.

I confirm and can explain it : by default, this filter computes the result with multiple cores when available, and to do this, it splits the image into several parts.
In your case, the parts of the images are very different from a statistical point of view, and the filter acts then differently on these different parts.
This is unfortunate, but there is a simple workaround : just select “Parallel Processing” → “One Thread” to solve the issue.

Would it be sensible to add a note to the filter?

Thanks everyone. That’s great to hear it’s easily fixable.

I agree that a note would be helpful, but I’d add that maybe 1 thread should be the default since this isn’t a super cpu intensive filter, (at least in my experience) and the note could indicate that you could speed it up if the image has an even distribution?


Most of the background was going to be obscured anyway so it was easier to just sharpen the entire image. I did end up cloning the unaffected area over to the left.

Also, is the reset parameters broken in this filter?

Shouldn’t be. Reset moves the parameters back to their default position.

I see. I guess the ability to reset parameters gets messed up after some updates. Mine wasn’t working, but after deleting and creating a new fave, everything works as expected.

Had a couple others that were acting up and was able to fix those as well.

Cheers.

I took the time this morning to look a bit closer to this filter.
The ‘Parallel’ option was in fact useless, as the filter was already natively parallelized, so I’ve removed the option. Same for Sharpen [Shock filters].