Hello world

,
I'm beginner in codeblocks (but not in unity3d & blitz3d programing), I would help with his tools ..
I want to create an application where I can capture the pixel position on the screen, to know its color, and free hand draw.
in short, process images (nothing exceptional).
but do not know how to use libraries or know the commands of them, and I would like you to indicate where to start.
can tell me?