Incase you don’t know the color to specify, try with floodfill:
1. Take 2 copies of your bitmap data.
2. Floodfill one of them with alpha value set to 0 in ARGB . Start fill from a corner. Ex:
bitmapData1.floodFill(1, 1, 0×00FFFFFF);
3. Now your bitmap data hides one object. Now copy that alpha channel using copyChannel() method into 2nd bitmap.
4. Inverse the alpha channel
Not tested, but worth a try.
^ Just checked the weekly popular files and from the top 25, only 5 files are made in AS2 . Remaining are either AS3 or a few AS2 +AS3
Feeling the same here, no wonder after 4 years of release!
Also performance improvements in player 10.1 and .2 can easily motivate people to make rapid switch to take advantage of AS3