Assignment 5

by Ebony McCoy

HTML

<button onclick="doDrawing();">Start Drawing</button>
<canvas id="myCanvas" width="400" height="400" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.</canvas>

JavaScript

var t = 0;
var r = 0;
var O = 50;
var c = document.getElementById("myCanvas");
var ctr = c.width/2;
var R = ctr/2;
var ctx = c.getContext("2d");

function doDrawing() {
    t = 0;
     r += 2*Math.random()-1;

    ctx.clear();
    
   
    var timesRun = 0;
    var color =  '#'+Math.floor(Math.random()*16777215).toString(16);
    
    var x = (ctr+(R+r)*Math.cos(t) - (r+O)*Math.cos(((R+r)/r)*t));
    var y = (ctr+(R+r)*Math.sin(t) - (r+O)*Math.sin(((R+r)/r)*t));   

    ctx.beginPath();
    ctx.strokeStyle = color;
    ctx.moveTo(x,y);
      
    var interval = setInterval(function(){
    timesRun += 1;
    if(timesRun === 500){
        clearInterval(interval); }
        
    drawSpirograph();}, 10); 
    
}
function drawSpirograph()
{
  t += 0.05;
  x = Math.floor(ctr+(R+r)*Math.cos(t) - (r+O)*Math.cos(((R+r)/r)*t));
  y = Math.floor(ctr+(R+r)*Math.sin(t) - (r+O)*Math.sin(((R+r)/r)*t));

  ctx.lineTo(x,y);  
  ctx.stroke();
}

CanvasRenderingContext2D.prototype.clear = 
  CanvasRenderingContext2D.prototype.clear || function (preserveTransform) {
    if (preserveTransform) {
      this.save();
      this.setTransform(1, 0, 0, 1, 0, 0);
    }

    this.clearRect(0, 0, this.canvas.width, this.canvas.height);

    if (preserveTransform) {
      this.restore();
    }           
};