I've just understand how to use bitblt to put non-rect objects into a picture box. This put my headache of pic update speed to and end but ... another problem arise :

How can I detect, when I click a point in a picture box area, that which object I'm clicking at? Like if I put a doughnut and say, detect if the clicked point is on the doughnut, not in the inner hole or ouside spaces? It is simple when I was using .click method before, but what should I do for this now? for bitblted object's click detection?