"Failed to execute 'toDataURL' on 'HTMLCanvasElement'" in a local web-page

[amcharts]

"Failed to execute 'toDataURL' on 'HTMLCanvasElement'" in a local web-page

[martynasma]

Well, I'm not sure about qt, but Chrome will never allow exporting the image when loaded locally. We're not aware of any workarounds, I'm afraid. Maybe it's not Chrome or qt, maybe it's the restriction of the rendering engine. I wish there was something more that we could do for you.

[martynasma]

This error means that you have an image loaded from different host than the web page itself ("tainted") OR you are loading this web page directly from the file system (file:///). Try loading it through web server. If the issue still persists, make sure that amCharts libraries are loaded from the same host as the web page displaying the chart itself.

[iprotsyuk]

Yes, I load the web-page directly from a file system. Actually, I'd like to embed amcharts into a native c++ app for graph visualization, that's why I'm looking for a solution without a web-server. Are there any options for this?

[martynasma]

That won't work I'm afraid, due to aforementioned browser security restrictions.

In this case you will need to embed your data as a JavaScript (JSON) code along the chart code.

I.e.:

var chartData = [{
  "category": "1",
  "value": 100
}, {
  "category": "2",
  "value": 110
}];

AmCharts.makeChart("chartdiv", {
  // ...
  "dataProvider": chartData,
  // ...
});

I hope this helps.

[iprotsyuk]

Yep, this is what I do, and everything works fine except the export plugin. I use qt webkit for html rendering, and I changed all its default security settings to allow working with local files, but it still gives me this security error.

Sorry for misleading you in the beginning. Chrome gives the same error with local files, and it uses webkit under the hood. As most of people are more familiar with chrome than qt webkit, I raised a bit different question, but I believe that the solution must be the same.

[iprotsyuk]

Alright, there's definitely a way to hack into html, pull an image out of canvas and pass it to the wrapping c++ code and save it afterwards. But of course, it would be easier for me to just use a working and tested solution. Thanks anyway.