Implementing a such program is not as easy as it seems. To Answer your question directly we need to know what are the
that you are using. I guess you are using
If you're using one of those API's, you should know about :
(or any other Graphics Library such as
is a good choice in small programs)
~ Handling messages properly (Mouse, Paint)
~ Undo Redo techniques, see here.
~ Handling Bitmaps
In GDI or GDI+ the key to develop a such program is about handling Memory-DCs and Bitmaps together with other Drawing functions.