I worked for a company that used ImageMagick for compositing images together and resizing them to one of ~60 sizes (different page locations, device types, etc.). While it worked, and it was at the core of the company's technology, it was truly the worst software I have ever had to wrangle into a production service.

You name it and ImageMagick could do it:

  - Leak memory
  - Perform terribly until you find the magic incantation that is 10x faster
  - Output wildly different images after a minor patch release
  - Remove / change options after a minor patch release
  - Enormously degrade performance after a minor patch release
  - Have numerous security vulnerabilities all the time, which require frequent upgrades
  - Dump core more often than you might like

It took us upwards of 3 months to simply move from one ImageMagick release to another (a few minor versions ahead), and we had to do all sorts of workarounds and A/B tests to ensure the images would look right.

I heard that GraphicsMagick was superior in that it maintained some consistency of behavior between versions, but it doesn't have all of the functionality of ImageMagick. So we couldn't switch to it.

Another company that I worked for had a fleet of several thousand servers running constantly just to thumbnail user uploaded images, and it was not unheard of for it to fall behind.

IM / GM are the stock answer to process images, but from my experiences they have no place in a production system. I think this is an area that is pretty poorly served by open source software; there are lots of libraries to handle different image formats, but no good infrastructure exists to tie it all together (that I'm aware of).