flash as2 BitmapData应用之 画双线

//根据此例子，可以实现划线带阴影的效果。。。
import flash.display.BitmapData;
import flash.geom.Rectangle;
import flash.geom.Point;
createEmptyMovieClip("draw_mc", -999);
createEmptyMovieClip("mm", -992);
var draw_bit:BitmapData = new BitmapData(Stage.width, Stage.height,true,0x226600);
/**/
var draw_;
//draw_mc._visible = false;
mm._x=mm._y=11;
draw_mc.onMouseMove = function() {
    //定义函数
    if (draw_) {
        draw_mc.lineStyle(4, 0xff0000, 100);
        //设置线条粗细、颜色、透明度
        draw_mc.lineTo(_xmouse, _ymouse);
        draw_bit.draw(draw_mc);
        mm.attachBitmap(draw_bit, 1);
    }
};
draw_mc.onMouseDown = function() {
    draw_ = true;
    draw_mc.moveTo(draw_mc._xmouse, draw_mc._ymouse);
};
draw_mc.onMouseUp = function() {
    draw_ = false;
};