Image manipulation

Hi,
I'm doing a project in Fingerprint Matching. I am beginning to code it now. There are a number of steps involved prior to minutia extraction and the comparison. I am not sure how to change the image in C++, I will be converting to gray-scale, smoothing, thinning it etc. How is the image accessed, how do I change the pixels individually?? Is it a two-dimensional array of numbers? If you help me with this I would be very grateful.
Thanks
-Colin:)

Thanks for the advice Salem. Wotsit has a lot of information that will help. I have lots to do!!
Thanks again,
-Colin.

after reading some of that, I think I want to try to make an image format, just for the heck of it.