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Getting weird pixel artifacts when using animated brushes

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Getting weird pixel artifacts when using animated brushes
Jan Thümmler Offline
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#1
09-18-2021, 07:15 PM
Hi there, newbe here.

I have been using GIMP for a couple of weeks now an am very pleased with my experience so far. I especially like the animated brush feature. Unfortunately I am getting some issues with it. Some custom animated brushes I set up for random scatter get very annoying artifact around the edges. I suspect they might have something to do with the alpha channel?

I am using GIMP 2.10.28 on a Win10 64bit PC and imported .png files I created in Photoshop to generate the animated brushes. As you can see in the attachment, the random scattered apples have these artifacts all around, while the coins I created earlier look just fine. Is there some option or knowledge I am missing? I really like the use of animated brushes and would be grateful for any help.

Thanks in advance
Jan


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rich2005 Offline
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#2
09-19-2021, 08:24 AM
This has been reported as a bug and it looks like no fix. https://gitlab.gnome.org/GNOME/gimp/-/issues/3686

It seems to be caused by a sub-pixel rendering effect, the paint tool brush is not aligned with the pixels grid. You can also get this effect using a brush and a dynamic where the brush is rotated when painting.
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Jan Thümmler Offline
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#3
09-19-2021, 10:34 AM (This post was last modified: 09-19-2021, 10:45 AM by Jan Thümmler.)
Aw dang.
Thanks for your answer. So is there a way to create brushes form scratch that are aligned with the pixels grid? I am already using a dynamic with rotation, so is the issue with the animated brush then? I'll try to experiment further, but i really like the use of multiple, randomly selected images for the brush.

[EDIT: I found a somewhat satisfying solution, thanks to your suggestion about using the regular brush, thanks a bunch!]
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PixLab Offline
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#4
09-19-2021, 11:29 AM (This post was last modified: 09-19-2021, 11:30 AM by PixLab.)
(09-19-2021, 10:34 AM)Jan Thümmler Wrote: [EDIT: I found a somewhat satisfying solution, thanks to your suggestion about using the regular brush, thanks a bunch!]

Can you please tell us more about this solution?
I got a kind of same problem with with my "on the fly" brush (Select/Copy, then use the "Image clipboard" brush), is it about number of pixels or size? or something else?
I'm very curious about your solution even if it a quoted "solution"
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rich2005 Offline
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#5
09-19-2021, 11:29 AM
As long as you get some solution that works with your images.

Just a note, stole some of your apples, this a comparison between a RGB gih brush and the same as a grayscale gih. No artifacts with the grayscale brush. Obviously not much use for apples but might come in handy sometime.

   
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Jan Thümmler Offline
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#6
09-19-2021, 01:51 PM
(09-19-2021, 11:29 AM)PixLab Wrote:
(09-19-2021, 10:34 AM)Jan Thümmler Wrote: [EDIT: I found a somewhat satisfying solution, thanks to your suggestion about using the regular brush, thanks a bunch!]

Can you please tell us more about this solution?
I got a kind of same problem with with my "on the fly" brush (Select/Copy, then use the "Image clipboard" brush), is it about number of pixels or size? or something else?
I'm very curious about your solution even if it a quoted "solution"

Well, I just created several normal brushes with just one image as the base and then mix them together to get the variety I want. Works most of the time (sometimes I still get artifacts, seems to be depending on the base image. Weird stuff, it would be so awesome if i could just scatter multiple images all over the place.

(09-19-2021, 11:29 AM)rich2005 Wrote: As long as you get some solution that works with your images.

Just a note, stole some of your apples, this a comparison between a RGB gih brush and the same as a grayscale gih. No artifacts with the grayscale brush. Obviously not much use for apples but might come in handy sometime.

OK interesting. I still have much to learn about GIMP ^^
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Ellye Offline
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#7
02-18-2024, 07:08 AM
(09-19-2021, 08:24 AM)rich2005 Wrote: This has been reported as a bug and it looks like no fix. https://gitlab.gnome.org/GNOME/gimp/-/issues/3686

It seems to be caused by a sub-pixel rendering effect, the paint tool brush is not aligned with the pixels grid. You can also get this effect using a brush and a dynamic where the brush is rotated when painting.
This bug is seriously affecting the progress speed in my current project.

From the issue tracker there, there seems to have been no fix on the 3+ years, right?

Is there a known work-around for it? Downgrading to 2.8 isn't really an option for me.
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