HTML5 Canvas Transformation

Javascript Web Development Front End Scripts

HTML5 canvas provides methods that allow modifications directly to the transformation matrix. The transformation matrix must initially be the identity transform. It may then be adjusted using the transformation methods.

Example

Let us see an example of canvas transformation:

<!DOCTYPE HTML>
<html>
   <head>
      <script>
         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');
               var sin = Math.sin(Math.PI/6);
               var cos = Math.cos(Math.PI/6);
               ctx.translate(200, 200);
               var c = 0;
               
               for (var i=0; i <= 12; i++) {
                  c = Math.floor(255 / 12 * i);
                  ctx.fillStyle = "rgb(" + c + "," + c + "," + c + ")";
                  ctx.fillRect(0, 0, 100, 100);
                  ctx.transform(cos, sin, -sin, cos, 0, 0);
               }
               ctx.setTransform(-1, 0, 0, 1, 200, 200);
               ctx.fillStyle = "rgba(100, 100, 255, 0.5)";
               ctx.fillRect(50, 50, 100, 100);
            } else {
               alert('You need Safari or Firefox 1.5+ to see this demo.');
            }
         }
      </script>
   </head>
   <body onload = "drawShape();">
      <canvas id = "mycanvas" width = "400" height = "400"></canvas>
   </body>
</html>

Krantik Chavan

Published on 11-Apr-2018 14:20:36

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