HTML5 Canvas - Animations


Advertisements


HTML5 canvas provides necessary methods to draw an image and erase it completely. We can take Javascript help to simulate good animation over a HTML5 canvas.

Following are the two important Javascript methods which would be used to animate an image on a canvas −

Sr.No. Method and Description
1 setInterval(callback, time);

This method repeatedly executes the supplied code after a given time milliseconds.

2 setTimeout(callback, time);

This method executes the supplied code only once after a given time milliseconds.

Example

Following is a simple example which would rotate a small image repeatedly −

<!DOCTYPE HTML>
<html>
   <head>
      
      <script type="text/javascript">
         var pattern= new Image();
         
         function animate(){
            pattern.src = '/html5/images/pattern.jpg';
            setInterval(drawShape, 100);
         }
         
         function drawShape(){
            // get the canvas element using the DOM
            var canvas = document.getElementById('mycanvas');
            
            // Make sure we don't execute when canvas isn't supported
            if (canvas.getContext){
            
               // use getContext to use the canvas for drawing
               var ctx = canvas.getContext('2d');
               
               ctx.fillStyle = 'rgba(0,0,0,0.4)';
               ctx.strokeStyle = 'rgba(0,153,255,0.4)';
               ctx.save();
               ctx.translate(150,150); 
               
               var time = new Date(); 
               ctx.rotate( ((2*Math.PI)/6)*time.getSeconds() + ( (2*Math.PI)/6000)*time.getMilliseconds() );
               ctx.translate(0,28.5);
               ctx.drawImage(pattern,-3.5,-3.5);
               ctx.restore();
            }
            
            else {
               alert('You need Safari or Firefox 1.5+ to see this demo.');
            }
         }
      </script>
   </head>
   
   <body onload="animate();">
      <canvas id="mycanvas" width="400" height="400"></canvas>
   </body>
   
</html>

The above example would produce following result −


html5_canvas.htm