We had to do some things at work using TIFF files with software thatrelied on the presence of certain TIFF Tags. We’re slowly phasing out some legacy C applications with Python equivalents, and decided to use Python Imaging Library for the task.
Everything worked brilliantly, aside from the fact that most of the tags from the original file we were modifying were getting wiped out in the newly saved file. This was a show-stopper, so I spent some time spelunking in PIL source and fixed the tag-obliterating behavior for the tags we were primarily interested in.
By no means is my work all-inclusive, but I did find some other minor bugs that probably weren’t noticed by most applications that were reading the resulting tiffs. Right now my modifications are sitting in a fork of the main repository on Bitbucket. I’ve got a pull request in with effbot, but until then, check out my work on the pil-2010-gtaylor fork. Comments, suggestions, and mean-spirited nit-picking are welcome.