HTML5 Game - Canvas Transformation Matrix

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Creating a custom transform

The HTML5 canvas API can define a custom transformation matrix that can be applied to the current context.

The following code creates a translational transform via the transform() method.

Demo

ResultView the demo in separate window 

<html>
    <head>
        <script> 
            window.onload = function(){
                let canvas = document.getElementById("myCanvas");
                let context = canvas.getContext("2d");
                /*  w  ww  .  j a va2 s .  c om*/
                let rectWidth = 150;
                let rectHeight = 75;
                
                // translation matrix:
                //  1  0  tx              
                //  0  1  ty
                //  0  0  1  
                let tx = canvas.width / 2;
                let ty = canvas.height / 2;
                
                // apply custom transform
                context.transform(1, 0, 0, 1, tx, ty);
                
                context.fillStyle = "blue";
                context.fillRect(-rectWidth / 2, -rectHeight / 2, rectWidth, rectHeight);
            };
        </script>
    </head>
    <body>
        <canvas id="myCanvas" width="600" height="250" style="border:1px solid black;">
        </canvas>
    </body>
</html>

Note

The code above created a custom translation transform via translation transformation matrix.

A transformation matrix is a 2-dimensional matrix.

It can be used to transform the current matrix.

The custom transformations can be applied to the context state using the transform(): 

context.transform(a,b,c,d,e,f);

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