问题
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 ?
回答1:
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);
回答2:
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.
来源：https://stackoverflow.com/questions/11391149/how-to-scale-imagedata-using-html5