Thanks, Simon. That alpha mask plugin looked like a great suggestion. Unfortunately, I tried it and I can't figure it out. I tried using it with the ScriptLab. What I did was install the Alpha Mask plugin and restart Paint.Net
I loaded my images and for the first image I started ScriptLab, then I selected Alpha Mask and saved the alpha mask as "temp.bmp" in the current directory. Then I selected Ink Sketch with 20% / 45% for the settings and applied that. Then I reselected Alpha mask and loaded the "temp.bmp" that I had saved previously. That didn't work right for some reason. The mask was wrong....
So, I tried it again but this time when I got to the part where I reloaded the Alpha Mask, I applied the filter without pulling the mask from the saved file and that worked! So, I was pretty happy but.... when I tried the same on next file, it trashed the alpha mask for some reason and used the first images alpha mask... Drat! Foiled again.
I tried several other variations on this theme and so far I haven't figured out how to actually use a combination of the Alpha Mask tool with the Ink Sketch filter to preserve the original alpha channel... What you suggested makes perfect sense, and I was pretty sure you were onto something there, but I haven't been able to get it to work right.
I am linking to an HTML page showing some more details.
http://www.wizardchat.com/colors/forum- ... tails.html
Export an alpha mask of the image, run the effect, then re-import it.
Plugin to do this: viewtopic.php?f=16&t=24191 (I linked to this as I have not tried the other plugins and this is the only one that am sure can export a mask as well.)