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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:
SN | 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. |
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 = '/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> |
Assuming we have following pattern images/pattern.jpg.
The above example would produce following result:
To learn above concept - Do Online Practice using latest version of either Safari or Opera.
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