Making a button with a picture

Question

I'm trying to make a button with a picture I made in photoshop.. but the problem is that the background is transparent, I just want the main part to be clickable.
Here is an example.. I just want the purple part to be clickable. The box around that is the actually whole image. So how can I fix this?

Answer 1

if you are using a simple button with up / over / down / hit frames do the following.
add a new layer to your button's timeline above the bitmap
in the up keyframe of this new layer draw a circle the same size and position of the purple starburst.
select the circle and cut the the circle (cmd-x or cntrl-x)
delete the layer you just made
make sure there is a keyframe in the hit frame of the remaining layer (f6)
if the bitmap is in the hit frame, delete it.
with the hit frame selected do a paste in place: cmd-shift-v or cntrl-shift-v
now you should have only the vector circle shape in the hit frame of the button.
now your button will only respond to mouse events when you rollover where the circle is.
the reason i had you add a new layer is because when you draw vectors in the same layer / frame as a bitmap, the vectors go behind the bitmaps and are hard to select, see, or modify.