Finding certain combinations of pixels on the screen... (and more)

Hi,

My first post here, hope its in its right place...

I would like to know how I could find certain combinations of pixels on the screen or on something like a bitmap. (both 32-bit color). If say I were looking for the letter 'A' (verdana or something) on the screen, how would a "sense" it?

Should I split up the screen in rows and columns and look for a particular combination of pixels or something like that?

The metod cant be to demanding, as I want to read the screen/bitmap at least once per second.

Any help/ideas will be greatly appreciated.

I prefer C++/C#/.NET

Also using GDI/GDI+

Thanks

JoPPeN