How to develop coloring pages application for iPhone/ iPad

I am developing an application in which I have 开发者_Go百科to develop coloring pages for kids. I have no idea about how to do it. So, I need start up hints. In which form the page will be presented? Will it be an Image? How to identify part of an image in page to fill with color? What else will help developing it?

I would start with a book on iPhone / Objective C development and work through the examples. Starting with basic labels, text fields and table views. Doing your own custom drawing based on user gestures will be easier to learn once you have a handle on the basics.

I would suggest using png with transparent areas for the areas which should be filled. Then coloring could be done on a deeper layer, so the borders of the shape aren't painted over. I would directly paint on the "coloring" layer. An eraser could easily be created as a white brush or whatever color the paper should have.