Hi,

Is there a way to specify the paintbrush's hardness via the C API for a non-generated brush? A plugin I'm developing creates quite a few brushes from PNGs with alpha layers, and when I use gimp_paintbrush() to 'stamp' a single instance of the brush on the canvas, any portions of the brush that have an alpha value less than 255 (i.e. are even partially transparent) are stamped with a lower alpha value than in the brush itself. Completely opaque elements of the brush are unaffected. I'm using Gimp 2.4.2 on Ubuntu 7.10 (Gutsy Gibbon).

I can reproduce this in the UI by simply using the paintbrush tool and clicking once on the canvas. If I check 'hardness' in the pressure sensitivity portion of the paintbrush's tool options, I get the desired behavior when painting manually (even though I'm using a normal mouse). I haven't been able to find a way to reproduce this from a plugin. Varying the paint application mode and/or the gradient length passed to gimp_paintbrush() doesn't do the trick.

So...

1. Is this a bug, or a feature?

2. If the latter, is there a way to avoid the fading via the C API?

I've written up a demo -- individual files may be found at http://www.sellner.org/drop/brush-fader/, while the tarball is at http://www.sellner.org/drop/brush-fader.tgz. It can be installed via gimptool, and installs into "/Filters/Generic/Brush Fader". When run, it takes the current image (which must be RGB) and generates a brush from it. The plugin then creates a new (blank) image, draws with the new brush, and creates a second brush from the result. This is repeated 4 times, creating a total of 6 progressively more transparent brushes. Finally, an example image is created with one instance of each of the 6 brushes. Since the act of painting onto the example image induces fading, the example image won't contain an unfaded copy of the brush image.

Running brush-fader against the two image files included in the tarball illustrates the effects: brush-fader-circle is a single instance of a standard fuzzy brush, and the outer 'fringe' slowly disappears. brush-fader-mountains was created with a tablet, doesn't have any completely opaque portions, and fades away entirely. The images that result from running brush-fader on the two examples are brush-fader-circle-results.xcf and brush-fader-mountains-results.xcf.

Thanks much,

-Brennan