It looks as though scripting-up the various modules is easier than building complicated script-processing in Photoshop. Seems that it would be easier to edit, at any rate.

I've worked with Photoshop--lo, these many years, now--and find that Actions are things that I avoid more often than not.

Plus, not everybody can afford P-shop, or has a sister working for a Univerisity that can get them an educational discount. A hypothetical sister, I mean. In which case, netpbm and the poorly-named Gimp would make a marvy combination.

I haven't used Photoshop since 2.5, so... To me the netpbm tools are ideal for bulk processing and non-interactive editing. Photoshop and GIMP are ideal for interactive stuff, localized editing, and one off filters.

When I get 30 gigs of TIFFs that are thousands of pixels wide and need to make web suitable jpegs, netpbm is my suite of choice. (I did this four weeks ago.)

When I need to cook up 10,000 unique images, each scaled to five sizes, netpbm is my suite of choice. (I did this last week, I used "ppmforge -clouds" as a base image and then superimposed id numbers on top with ppmlabel, and then ppmarithed a very large last digit in, since the id number was hard to read at the smallest size.)

When I wanted to make a selection of ascii characters on different colored backgrounds to experiment with ascii art from GIMP's photo mosaic tool, I used pbmtext to make base B&W images and ppmchange to colorize them. One million files and twelve hours of cputime later I was disappointed with the resulting mosaic, but I wouldn't have even attempted it without netpbm.

That said, I also use netpbm when I want to experiment with settings, by say, changing each of several successive filters by a little bit in nested loops and looking at the dozens or more files that come out to find the best combination. Similar stuff can be done interactively editing, undoing, trying again, but this way I can let the cpu work while I read tribe.net or Usenet.