Brush problem

[PixLab]

Here is the brush, there is no other colors, than white, red, green.

   

Load it as an image in GIMP
Ctrl + A then Ctrl + C
Create new doc then Select that brush (Clipboard Image, first in the brush list)
Spacing 1
Force 70
   

Make a square....
do you got some black stripes?

Even worse...
Try Dynamics / Untitled >  Edit dynamics check "angle with Fade"
   

Fade length ~100
Repeat > Sawtooth wave (or any repeat will do)
   

Make a square...
Is it only me getting those black things?

   

So I tried to save it as a brush.gbr and put it in the brushes folder => same things happening
I tried also to select without feather =0 > shrink 3 pixels
same thing is happening but sharper....
And if you change the size of the brush (like smaller) it's even worse than above

Patterns that I saw (it's more obvious with dynamics):
drawing right to left is better (less black)
drawing bottom to top is better (less black)
drawing left to right is the worst
drawing top to bottom is the worst as well
reducing Force below 30 have a better effect, (less black parasites) but the candy alike is not sharp enough anymore > and goes on the blur side...

I'm getting out of ideas...
buntu 20.04, GIMP 2.10.24/25 PPA/appimage
did try also on my kid computer > MX Linux 19.4 GIMP from the original repo (Debian) 2.10.24, same problem

[programmer_ceds]

(08-21-2021, 04:35 AM)PixLab Wrote: Here is the brush, there is no other colors, than white, red, green.



Load it as an image in GIMP
Ctrl + A then Ctrl + C
Create new doc then Select that brush (Clipboard Image, first in the brush list)
Spacing 1
Force 70


Make a square....
do you got some black stripes?

Even worse...
Try Dynamics / Untitled >  Edit dynamics check "angle with Fade"


Fade length ~100
Repeat > Sawtooth wave (or any repeat will do)


Make a square...
Is it only me getting those black things?



So I tried to save it as a brush.gbr and put it in the brushes folder => same things happening
I tried also to select without feather =0 > shrink 3 pixels
same thing is happening but sharper....
And if you change the size of the brush (like smaller) it's even worse than above

Patterns that I saw (it's more obvious with dynamics):
drawing right to left is better (less black)
drawing bottom to top is better (less black)
drawing left to right is the worst
drawing top to bottom is the worst as well
reducing Force below 30 have a better effect, (less black parasites) but the candy alike is not sharp enough anymore > and goes on the blur side...

I'm getting out of ideas...
buntu 20.04, GIMP 2.10.24/25 PPA/appimage
did try also on my kid computer > MX Linux 19.4 GIMP from the original repo (Debian) 2.10.24, same problem

Not quite as dramatic as you describe but the dithered pixels around the edge of the circle are causing streaks of colours that are not the pure white, green and red of the png file when I draw with it as the brush. Could these pixels be connected with the problem?

[PixLab]

(08-21-2021, 12:56 PM)programmer_ceds Wrote: Not quite as dramatic as you describe but the dithered pixels around the edge of the circle are causing streaks of colours that are not the pure white, green and red of the png file when I draw with it as the brush. Could these pixels be connected with the problem?

Thanks to had a look at it.
Did you got the same on Windows? If so, do you think it's a bug?

[programmer_ceds]

(08-22-2021, 03:08 AM)PixLab Wrote:

(08-21-2021, 12:56 PM)programmer_ceds Wrote: Not quite as dramatic as you describe but the dithered pixels around the edge of the circle are causing streaks of colours that are not the pure white, green and red of the png file when I draw with it as the brush. Could these pixels be connected with the problem?

Thanks to had a look at it.
Did you got the same on Windows? If so, do you think it's a bug?

What I was seeing was caused, I think, by the pixels that were not solid colour. You could use a 1 pixel hard brush with the pencil to make these pixels either solid white, green or red and then see what happens.

[PixLab]

(08-22-2021, 07:48 AM)programmer_ceds Wrote: What I was seeing was caused, I think, by the pixels that were not solid colour. You could use a 1 pixel hard brush with the pencil to make these pixels either solid white, green or red and then see what happens.

Did tried this as well (no fading between color and transparency, pure harsh raw pixel) = Same problem, but sharper

(08-21-2021, 04:35 AM)PixLab Wrote: I tried also to select without feather =0 > shrink 3 pixels
same thing is happening but sharper...

[PixLab]

Can some one try this -> https://youtu.be/Ynr2TzNz3MA?t=119 ?
brush spacing 1
During your test, Is it as clean as on the video? especially if you resize to a lower size

[rich2005]

I think it is this bug: https://gitlab.gnome.org/GNOME/gimp/-/issues/5509

Rotating the brush introduces (semi-)transparent pixels, which show black especially over the white quarters.

I tried all ways, hard edge brush, anti-aliased brush, all the precisions, all the modes, without success.

[PixLab]

(08-23-2021, 03:02 PM)rich2005 Wrote: I think it is this bug: https://gitlab.gnome.org/GNOME/gimp/-/issues/5509

Rotating the brush introduces (semi-)transparent pixels, which show black especially over the white quarters.

I tried all ways, hard edge brush, anti-aliased brush, all the precisions, all the modes, without success.

Thanks to have tried Rich. (also @programmer_ceds, thanks a lot for your inputs)
I think, that's not the same bug (I think), he got white problem when rotating picture AND exporting jpg,
for this one we do not need to rotate the brush to see the black, but yes when rotating the brush it's way-way worse.

I did tried with GIMP back to 2.10.12 (.13 appimage) bug was there already...

I'm gonna fill a bug report tomorrow