I'm trying to use [binfile] ([mrpeach/binfile]) to generate a jpg that is filled with randomly coloured pixels. A search on the internet revealed that all jpgs need to start with "255 216 255" and end with "255 217". I opened up a few jpgs and can confirm that this is the case

I've created a patch (attached) that does this but the output can't be read by any programs. IS this an error in Pd (e.g. is it adding extra data) or are there some other rules about jpgs that I don't understand?

http://www.pdpatchrepo.info/hurleur/generate_jpg.pd

Don't rightly know, but when I glitch something and it breaks the file, I can sometimes fix it using imagemagick. If you have imagemagick, try:

$convert img.jpg img_fixed.jpg

I finally managed to do this. I wrote a tutorial documenting the process. Here's what the output looks like