If you have any ethics or care about security, a free(libre) license software is really the only way to go. So for my IT students I recommend GIMP and Inkscape. The learning slope is not too steep. They have pretty much all the graphics power you ever need, and for scripting I would use either Imagemagick or the Python image manipulation libraries.
Then I would ask, why would anyone ever risk using closed source proprietary software? With the FLOSS alternatives there is no reason.