GNOME Bugzilla – Bug 399221
Pixel artifacts when drawing with brush scaling and generated brushes
Last modified: 2007-03-16 14:19:55 UTC
To reproduce: create a new generated brush, set it radius to a non integer value (like 32.1), paintbrushtool, set brush scaling on tool option to something between 0.75 and 0.99 (best with 0.97). Try and paint something. There are less artifactes if the brush radius is an integer value (like 32.0), but they also show up, suggesting a rounding problem somewhere. Also, there are far less artifacts if spikes is set to "3" instead of 2. But that can lead to a segmentation fault. As the two may not be related I will open a second bug report. So, scaling a .vbr is not needed at all in normal usage, why am I marking this one as "critical"? Because when painting with a tablet, with "size" checked on the pressure options will trigger the artifacts. There is no easy work around to these artifacts - one is indeed prevented from making the best usage of changing a brush tip size with the pressure.
Forgot to mention I am on a x86_64 Linux system.
Created attachment 80852 [details] Small screen shot showing the reported problem I'm seeing the same thing with GIMP built from SVN (revision 21750) on an i686 machine. I created a new feathered brush and set the size to 16.1 and drew a line with the pencil using 0.97 as the radius.
Additional information: If the brush size is set to 16 or the scale is set to 1 the artifacts are not seen.
As the new brush resizing algorithm, that allows upscaling, takes place, this one is gone.
So how does the new brush resizing algorithms affect generated brushes? They shouldn't be used here at all, or am I missing something?
r22113 made some changes to gimpbrushgenerated.c 2007-03-14 Martin Nordholts <martinn@svn.gnome.org> (...) * app/core/gimpbrushgenerated.c: Implemented the new scale_size method inherited from GimpBrush, and modified gimp_brush_generated_calc to use this helper function. I'd say that removed the buggy part.