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HTML5 Canvas - Translation
HTML5 canvas provides translate(x, y) method which is used to move the canvas and its origin to a different point in the grid.
Here argument x is the amount the canvas is moved to the left or right, and y is the amount it's moved up or down
Example:
Following is a simple example which makes use of above method to draw various Spirographs:
<!DOCTYPE HTML>
<html>
<head>
<script type="text/javascript">
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.fillRect(0,0,300,300);
for (i=0;i<3;i++) {
for (j=0;j<3;j++) {
ctx.save();
ctx.strokeStyle = "#FF0066";
ctx.translate(50+j*100,50+i*100);
drawSpirograph(ctx,10*(j+3)/(j+2),-2*(i+3)/(i+1),10);
ctx.restore();
}
}
}else {
alert('You need Safari or Firefox 1.5+ to see this demo.');
}
}
function drawSpirograph(ctx,R,r,O){
var x1 = R-O;
var y1 = 0;
var i = 1;
ctx.beginPath();
ctx.moveTo(x1,y1);
do {
if (i>20000) break;
var x2 = (R+r)*Math.cos(i*Math.PI/72) -
(r+O)*Math.cos(((R+r)/r)*(i*Math.PI/72))
var y2 = (R+r)*Math.sin(i*Math.PI/72) -
(r+O)*Math.sin(((R+r)/r)*(i*Math.PI/72))
ctx.lineTo(x2,y2);
x1 = x2;
y1 = y2;
i++;
} while (x2 != R-O && y2 != 0 );
ctx.stroke();
}
</script>
</head>
<body onload="drawShape();">
<canvas id="mycanvas" width="400" height="400"></canvas>
</body>
</html>
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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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