i need help in graphics

This is probably inefficient,
You could probably save the backbuffer (rendering surface) using some time interval and when the person wishes to undo the change you could just retrieve the previous saved backbuffer (rendering surface).
You could also look at GDI+ and saving the drawing parameters in a list
This should give you some ideas on how to go about thinking of your own solution...

I hope this helps.
Take care.