[Gimp-user] Custom brush spacing issues

[N75 <forums gimpusers com>]

...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".

-- 
N75 (via www.gimpusers.com/forums)