the constructor accepts two other parameters, the 3rd is transparency and the 4th is background color:
tf.text = my_txtS;
var bm:BitmapData = new BitmapData(tf._width, tf._height,false,0xff0000); // for a red background
tf._visible = true;
oooohhhhhh, that's great
thanks a lot!
I just tested it, working amazing, thanks again,
just want to add a bit of info, in order to make the 3rd parameter work you need the fourth as well, regardless you need a color background or not.