I have built, and got working, a polar graphic plotter. The machine uses a processing sketch, which scans from left to right, top to bottom, on an image, (much like an old CRT scans an image). The data is churned out onto an arduino which plots the image.
it currently producesdiamond images: I use Gimp, to manually rotate the image through 135 degrees. The "top left" of the image,  actually becomes the bottom point of the image.



I want to produce "square" not "diamond" images, while maintaining the 45 degree line passes (as a necessity, due to the way the plotter works)

Heres a vid should you be interested!
http://www.youtube.com/watch?feature=player_embedded&v=5SB8V-LM_NM

does anyone have any suggestions for scanning an image at 45 degrees, rather than left to right.

I suppose instead of looping around, adding 1 to x every time, i could add 1 to both X and Y, simultaneously, but would need to keep track of the "edge" of the image, as each pass will be of a different length.
Is there a function for detecting the edge of an image?

suggestions greatly appreciated!
cheers

Ol