html5 canvas 加载图片错误 SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement'

html5 canvas 加载图片错误 SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported

原因：跨域加载图片

解决方案：
javascript ：

<img src="your_domain.com/img.png" crossorigin="Anonymous" />

<script>
var image = new Image();
image.crossOrigin = "Anonymous";
...
</script>

server 返回的http response中要加以下值到header：

Access-Control-Allow-Origin "*"