As far as I know, most of my PbP DMs do that in Photoshop/GIMP.
So, I am in a play by post game and the DM posts images. The problem is that he references grid positions by cell, but does not have the labels and some of the images are quite large (ie, in number of cells). Is there an easy way to print labels on two edges of an image chess style (eg: A5, E10, etc)?
My Finished Maps
Works in Progress(or abandoned tests)
My Tutorials:
Explanation of Layer Masks in GIMP
How to create ISO Mountains in GIMP/PS using the Smudge tool
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Unless otherwise stated by me in the post, all work is licensed under a Creative Commons Attribution-Noncommercial 3.0 United States License.
As far as I know, most of my PbP DMs do that in Photoshop/GIMP.
"Unless I'm allowed to carry around a gun to shoot their giant killer-spiders, Australia needs to stay the hell away from me. Also Australians, who if they have lived this long are obviously agents of the spiders and not to be trusted."
Well that would depend on how professional you want it to look. If I understand the situation correctly you want to mark a map that you have a copy of, in this case I would go old skool with a pen (or if I'm in character a sharpened stick dipped in the dogs blood)