谢尔宾斯基三角形.js

var c=document.getElementById("XcCanvas");
var ctx=c.getContext("2d");
ctx.drawPoint = function (point) {
    var x, y, size;
    if (arguments.length === 2) {
        x = arguments[0];
        y = arguments[1];
    } else {
        x = point.x;
        y = point.y;
        if (point.color !== undefined) {
            this.fillStyle = point.color;
        };
        if (point.size === undefined) {
            x = Math.floor(x);
            y = Math.floor(y);
            size = 1;
        } else {
            x = Math.floor(x - point.size/2);
            y = Math.floor(y - point.size/2);
            size = point.size;
        }
    }
    this.fillRect(x, y, size, size);
};
ctx.translate(10, 10);
ctx.fillStyle="#FF0000";

var Point = function (x, y) {
    this.x = x;
    this.y = y;
};
Point.prototype.setColor = function (color) {
    this.color = color;
    return this;
};
Point.prototype.setSize = function (size) {
    this.size = size;
    return this;
};

var getTriangleTreePoint = function(a) {
    return [
        new Point(a/2, 0).setColor('#FF0000').setSize(5),
        new Point(0, a*Math.sqrt(3)/2).setColor('#00FF00').setSize(5),
        new Point(a, a*Math.sqrt(3)/2).setColor('#0000FF').setSize(5)
    ];
};
var drawTreePoint = function (a) {
    var PointList = getTriangleTreePoint(a);
    for (var i = 0; i < PointList.length; i++) {
        ctx.drawPoint(PointList[i]);
    };
};

var getRandomPoint = function(a) {
    var sqrt3 = Math.sqrt(3);
    var getRandomPointIter = function () {
        return {x: Math.random()*a, y: Math.random()*a};
    };
    var point;
        point = getRandomPointIter(a);
            return point;
}

var a = 400;
drawTreePoint(a);

var StartPoint = getRandomPoint(a);
StartPoint.color = "#000000";
StartPoint.size = 8;
ctx.drawPoint(StartPoint);
var getMidPoint = function (p1, p2) {
    return {x: (p1.x + p2.x) / 2, y: (p1.y + p2.y) / 2, color: p2.color};
};
var chooseOnePointFromTree = function (a) {
    var index = Math.floor(Math.random()*3);
    var point_list = getTriangleTreePoint(a);
    return point_list[index];
};
var p;
var MidPoint;
var i = 0;
var iter = function () {
    p = chooseOnePointFromTree(a);
    MidPoint = getMidPoint(StartPoint, p);
    ctx.drawPoint(MidPoint);
    StartPoint = MidPoint;
    if (i < 40000) {
        setTimeout(iter, 1);
    };
    i++;
};
iter();
console.log('end');