> How is that even relevant? Images cost in bandwidth, not in computing power.

Sounds like you need to do some STFU yourself, having clearly never come anywhere near this problem domain. Using standard tools to process and resize user-uploaded images can easily soak up all the CPU time and memory you could throw at it.

I recently spent a bunch of time rewriting a client's image processing pipeline fromt the usual O(n)-space ImageMagick crap that loads the full uncompressed image into memory a few times over to be O(1)-space doing streaming downsampling by exploiting the compression implementations of JPEG and PNG. It was more than worth it — even with the PNG implementation being a bit more CPU intensive now, it's a lot nicer having it operate in constant space without fear of swap and the OOM-killer.