Copyright law information on image alteration?

Here is the deal, I have no idea about copyright information and would like to find out. Ok say i take an photo image of someperson. I want to cartoonize over the image like a template, the finished product is an cartoon image that only holds the same shapes as the photo but has been painted over. The image afterwards looks different then the original with come custom changes. I consider this a form of art but unsure if you can do this and sell the material since it resembles someone since it was painted over. The overall product isnt an exact duplication but a product of said template. can anyone give me some web page material to help me understand copyright. Thanks