javascript - SecurityError: The operation is insecure in canvas.toDataURL

Question

I've tried to resolve the next error but without success.

I have the following jQuery and HTML5 code:

<script language="javascript" type="text/javascript">

  function doExportMap() {

      map.once('postcompose', function(event) {

        var canvas = event.context.canvas;

        var exportBMPElement = document.createElement('a');
        exportBMPElement.download = 'Mapa.bmp';
        exportBMPElement.href = canvas.toDataURL('image/bmp');
        document.body.appendChild(exportBMPElement);
        exportBMPElement.click();
        document.body.removeChild(exportBMPElement);
      });

      map.renderSync();
  }

It was working perfectly way, but now, I'm getting the following error:

SecurityError: The operation is insecure.
exportBMPElement.href = canvas.toDataURL('image/bmp');

What is wrong? Any ideas?

The funny is that I'm not loading the image from an external source. The image is from localhost

Answer 1

It would be helpful if you could post the code you are using to modify the canvas before attempting to export it. With the information you provided, my guess would be that you are writing content from an external source to your canvas. This is why it was working before and is no longer working. I assume your initial tests used a resource from the same origin.

---

Explanation

The same security sandbox exists with the canvas as does with any data requests being made from your code. Anytime you load content from another domain/origin it will trigger the canvas to set the origin-clean flag to false. This means the browser will prevent you from exporting data that has been loaded into the canvas. There are quite a few posts pertaining to this type of issue on StackOverflow:

• canvas.toDataURL() Security Error The operation is insecure
• Security Error with canvas.toDataURL() and drawImage()