天津 亚惠:关于一个flash遮罩代码的问题

znum = 0;
_root.img.setMask(_root.mov);
allz = new Array();

allz[0] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10];
allz[1] = [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9];
allz[2] = [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8];
allz[3] = [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7];
allz[4] = [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6];
allz[5] = [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5];
allz[6] = [7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4];
allz[7] = [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3];
allz[8] = [9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2];
allz[9] = [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1];
for (i=0; i<30; i++) {
for (j=0; j<10; j++) {
_root.mov.nemo.duplicateMovieClip("m"+(i-1)*30+j, (i-1)*30+j);
_root.mov["m"+(i-1)*30+j].xnum = i;
_root.mov["m"+(i-1)*30+j].ynum = j;
_root.mov["m"+(i-1)*30+j]._x = i*20+0;
_root.mov["m"+(i-1)*30+j]._y = j*20+20;
_root.mov["m"+(i-1)*30+j].onEnterFrame = function() {
if (_root.allz[this.ynum][this.xnum] == _root.znum) {
this.play();
}
};
}
}

_root.onEnterFrame = function() {
if (znum<21) {
_root.znum++;
}
};

如果现在我的图片跟场景放大了，应该怎么改才能把图片全遮罩？