the image's dimension are determined by it's filename. for best results stick to the original filename during this format conversion.

eg. if you want to create a personilized poweron picture:

1. convert /image/poweron/01.art into 01.png
2. use your favorite image editor to make your changes
3. convert 01.png back into art format and save / replace original 01.art file
4. continue with /image/poweron/02.art, and so forth

alpha is 1bit, first (?) pixel, converted color is #FFFBFF