image processing API

i might be doing a project on image processing; dont know the exact functionality yet, but from what i gather it has something to do with image histograms and color vectors of jpeg files; basically its about feature extraction of those color vectors using some sorta java image API.
i wanna know which API's shud i go thru before starting off, i mean, those concerning jpeg image processing and color vectors.
i know all this sounds too vague, my profound apologies.

Try the Java Advanced Imaging Tutorial.