Thanks for the reply. I appreciate it.
I tried the suggestion of increasing resolution by factor of 10 (from 1200 dpi to 12000 dpi) but as that reduced the physical size by a factor of 10 the problem with being able to distinguish tics became vastly worse (the whole ruler had only one labeled tic). Uping the physical size to compensate takes the ruler tics back to where they were (difficult to discern) but in the process messes up the artwork (resampling was set to bilinear). I cannot go in the other direction (lower resolution) because the lines would then come out poorly in a reduced size printed version.
I attached an image of the ruler in a separate e-mail to you so you could see what I am talking about. (I do not know how to include in this post an image that does not have a URL on the web.).
If the code for the tic lengths is part of a relatively small .cs file that produces its own .dll (so that I could see the results of changes) and if you were interested in letting me look at, I would be happy to see if I could do any good. (I work in VS 2008 and have written code to automatically adjust a distance scale while zooming.)
Background wise, I am comfortable in much of C# and VS but am a novice with respect to raster images.
By the way, thanks for paint.net. I find it to be a wonderful program.