How to scale ImageData using HTML5?

2019-07-13 03:10发布

Particularly i have this example but it does not seem to work :

<!DOCTYPE html>
<html>
<body>

<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">
your browser does not support the canvas tag </canvas>

<canvas id="myCanvas2" width="300" height="150" style="border:1px solid #d3d3d3;">
your browser does not support the canvas tag </canvas>

<script type="text/javascript">

var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");

var c2=document.getElementById("myCanvas2");
var ctx2=c2.getContext("2d");

ctx.strokeRect(5,5,25,15);
var imageData = ctx.getImageData(0,0,c.width, c.height);


ctx2.putImageData(imageData, 100, 100);
ctx2.scale(2,2);
</script> 

</body>
</html>

Shouldn't the rect get scaled in the second canvas ?

标签： html5 canvas scale

2条回答

爷、活的狠高调

2楼-- · 2019-07-13 04:06

You need to do the transformation before you "write" the image into canvas.

ctx2.scale(2,2);
ctx2.putImageData(imageData, 100, 100);

Then everything should work fine.

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傲

3楼-- · 2019-07-13 04:13

Try the following code:

var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");

var c2=document.getElementById("myCanvas2");
var ctx2=c2.getContext("2d");

ctx.strokeRect(5,5,25,15);

ctx2.scale(2, 2);
ctx2.drawImage(c, 10, 10);

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How to scale ImageData using HTML5?

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