A brief outline of the steps needed on a desktop computer or device to "posterize" a photograph for use in laying out a painting.

Used in
Adobe Photoshop CS3
Notanzer app from #bigpantsgroup http://www.bigpantsgroup.com/
Gimp software from https://www.gimp.org/

Other possible software and apps:

Posterize in
Adobe Photoshop (best, #levels and brightness control)
Adobe Photoshop Elements ($99, perspective crop, posterize)
Microsoft Word (image Filter “Paint strokes”)
Sporkforge.com (free online, 2 values, lo res)
Windows Live Photo Gallery (adjust histogram)
Corel Painter (posterize)
pinetools.com (free online, choose # values, med res)
IMGonline.com.au (free online, choose # values, good res)

http://posterize.imageonline.co (free online, choose #value, good res
Apps iPhone
poster shine pro (choose # value, good full res