Moses Gunesch, creator of Fuse Kit and ZigoEngine , has developed an AS3 Class which handles mouse interactions when dealing with transparent PNG’s.
Here is the theory:
If you have a PNG (one that contains transparent areas) embedded inside of a MovieClip button, the rectangle of the image acts as the hitArea of the MovieClip. In order for the hitArea to only be defined by visible areas of the image, you would normally have to create a custom mask in order to hide the transparent areas of the PNG. This AS3 Class allows you to specify an alpha tolerance (0=transparent, 255=completely opaque), that will allow you to selective exclude the transparent areas from your hitArea based on the value that you give it. This is a very simple concept, but an intricate implementation.
The project is open-sourced under the MITÂ Open Source License. Go and check it out:
