This is by far my most common task, and I'd say I've wasted about 1000 mouse clicks on it in my raster-based program.

Because it's so common for me to start off desaturating an image and then posterizing it, I'd like to write a shell script that does the same, that way I can process an entire directory automagically and simply get on with my work... There are only so many hours in the day. If I can make my computer do all the mouse clicks for me, go away and drink a few cups of coffee while it does so, then come back to it, that's infinitely better for me.

So how can I accomplish these two tasks using the CLI?

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    It'd help to mention GIMP in your question. Took me a few minutes to figure out what app you were using! I don't have an answer for you but am interesting in seeing if others come up with. An easy way to script The GIMP would be useful. There is Script-Fu, though I haven't looked at that in much detail: docs.gimp.org/en/gimp-concepts-script-fu.html – DA01 Jan 20 '11 at 16:19
  • What are doing this with now? There might be scripting-based, non-CLI options available to you in your current set of tools. This, of course, largely depends on whether your application of choice offers an API to target a script. – Philip Regan Jan 20 '11 at 16:24
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    @ixt "Command line" might be a reasonable translation that works on a non-IT-centric site. – Pekka Jan 20 '11 at 21:09
  • @DA01, I'm not asking for an application-specific method. Unfortunately the graphics design community does not seem to have vocabulary that crosses the boundaries drawn by operating systems. – ixtmixilix Jan 20 '11 at 21:11
  • Uh...you tagged in GIMP. Are you not using The GIMP? – DA01 Jan 20 '11 at 21:26

ImageMagick is the most awesome and powerful CLI image editing tool I know. It runs on most operating systems.

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  • +1 for linking to the discussion about desaturation. I already knew how to do it this way and found it unsatisfactory since ImageMagick doesn't give you as many options for desaturation as GIMP does. Otherwise the -posterize parameter does exactly what I need. So I may end up doing it by using one big script that makes a call to both GIMP and ImageMagick. – ixtmixilix Jan 20 '11 at 21:06
  • @ixt I can relate! I never managed to get my head around the alchemies of GIMP, either. :) – Pekka Jan 21 '11 at 15:46
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    Ever since I learned of ImageMagick I use it all the time in Python scripts to batch process entire directories of images. – jhocking Apr 9 '11 at 21:56

This is typically called batch processing and GIMP supports it. More info:


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