Example Processing script

by Andrew Wooldridge

HTML

<h1>Processing.js</h1>
<h2>Simple processing.js via JavaScript</h2>
<p>Clock</p>

<p><canvas id="canvas1" width="200" height="200"></canvas></p>

JavaScript

// Simple way to attach js code to the canvas is by using a function
function sketchProc(processing) {
  // Override draw function, by default it will be called 60 times per second
  processing.draw = function() {
    // determine center and max clock arm length
    var centerX = processing.width / 2, centerY = processing.height / 2;
    var maxArmLength = Math.min(centerX, centerY);

    function drawArm(position, lengthScale, weight) {      
      processing.strokeWeight(weight);
      processing.line(centerX, centerY, 
        centerX + Math.sin(position * 2 * Math.PI) * lengthScale * maxArmLength,
        centerY - Math.cos(position * 2 * Math.PI) * lengthScale * maxArmLength);
    }

    // erase background
    processing.background(224);

    var now = new Date();

    // Moving hours arm by small increments
    var hoursPosition = (now.getHours() % 12 + now.getMinutes() / 60) / 12;
    drawArm(hoursPosition, 0.5, 5);

    // Moving minutes arm by small increments
    var minutesPosition = (now.getMinutes() + now.getSeconds() / 60) / 60;
    drawArm(minutesPosition, 0.80, 3);

    // Moving hour arm by second increments
    var secondsPosition = now.getSeconds() / 60;
    drawArm(secondsPosition, 0.90, 1);
  };
  
}

var canvas = document.getElementById("canvas1");
// attaching the sketchProc function to the canvas
var p = new Processing(canvas, sketchProc);
// p.exit(); to detach it