curveTo加强版的曲线效果

//points是控制点的数组，t是精度吗？n是阶（其实就是控制点的个数）
function bezier(points, t, n) {
var arr = new Array();
for (var i = 0; i<n; i++) {
var temp = new Object();
temp.x = points[i].x;
temp.y = points[i].y;
arr.push(temp);
}
for (var r = 1; r<n; r++) {
for (var i = 0; i<n-r; i++) {
arr[i].x = (1-t)*arr[i].x+t*arr[i+1].x;
arr[i].y = (1-t)*arr[i].y+t*arr[i+1].y;
}
}
return (arr[0]);
}
///////////////////////////////////////////////////////////////////////
var points_arr:Array = new Array();
init();

function doMouseDown() {
_root.clear();
_root.lineStyle(1, 0x0000ff, 15);
for (var i = 0; i<points_arr.length; i++) {
if (i == 0)
_root.moveTo(points_arr[i].x, points_arr[i].y);
_root.lineTo(points_arr[i].x, points_arr[i].y);
}
_root.lineStyle(1, 0xff0000, 100);
n = points_arr.length;
k = 5*n;
for (var i = 0; i<=k; i++) {
var t = i/k;
var point = bezier(points_arr, t, n);
if (i == 0)
_root.moveTo(point.x, point.y);
_root.lineTo(point.x, point.y);
}
if (points_arr.length>20)
points_arr = new Array();
}
///////////////////////////////////////////////////////////////////////

function init() {
l = new Object();
l.onMouseDown = function() {
var point = new Object();
point.x = _xmouse;
point.y = _ymouse;
points_arr.push(point);
if (onEnterFrame != undefined) {
delete onEnterFrame;
points_arr = new Array();
}
};
l.onMouseUp = doMouseDown;
Mouse.addListener(l);
_root.onEnterFrame = function() {
_root.clear();
_root.lineStyle(1, 0xff0000, 100);
var point = new Object();
point.x = 500*Math.random();
point.y = 500*Math.random();
points_arr.push(point);
_root.lineStyle(1, 0xff0000, 100);
doMouseDown();
};
}