Cover entire movie clip

I have been trying to come up with a way to get the borders of a movie clip (lets say a triangle) and place a smaller movie clip on each pixel or every certain number of occurring pixels in order to cover the entire movie clip (triangle). what i’m trying to do is place small blades of grass that cover an entire movie clip with actionscript, that do not go over the movieclip’s borders. does anyone know how to do this or where to get a head start?