get objects from image

[Jannis Syntychakis]

Hallo Everybody,

Maybe you can help me with this:

i have a picture. The picture is black, with some white objects.

Is there any way i can detect the automatically? Something like:
if there white objects bigger than 3 pixels draw a box there or get
their
position!

getting their position is more important for me.

One more question:"

can i let the user tell the software there the white object is? like a
square
this moves with the mouse and the user will be able to click on the
white objects.

Maybe somebosy could help? with an example maybe?

Thank you very much in advance!!!!

Ioannis