...just so we're on the same page, I'm using GIMP v2.8.10

I'd like to know if there's a calculation I can do to work out the precise spacing of a custom brush, based on the original image width/canvas width (and possibly height? I've noticed that changing the height of the canvas does eventually have some effect).

The brush I'm working on is best described as technical and requires precise spacing for stroke/straight line painting. I was thinking that if I know the spacing calculation, I could work it backwards, and make sure that my brush image/brush canvas size complies with the program's mechanics.

As it is, my brush canvas is 512px wide, 822px high, and I've got spacing set to 84.1, but given the "underlap" I'm getting it should probably be 84.15. If I set it to 84.2 then I get an overlap.

Umm, and just saying: it would be really nice if I could set brush spacing to pixels, rather the GIMP's does-not-seem-to-make-sense spacing figures. Though it'll probably* make sense if I know how the program calculates spacing.

Thanks in advance.

-N

*I'm mathematically challenged. That "probably" should actually read "yeah, probably NOT".