title: Converting Chart.js canvas chart to image using .toDataUrl() results in blank image
body: <p>I am using Chart.js. I am trying to convert the chart to an image by getting a base 64 string. The tutorial (<a href="http://www.chartjs.org/docs/" rel="noreferrer">http://www.chartjs.org/docs/</a>) devotes an entire 1 line on the topic:</p>
  
  <blockquote>
    <p>The canvas element also allows for saving the contents as a base 64
    string, allowing saving the chart as an image.</p>
  </blockquote>
  
  <p>A <code>canvas</code> element has the method of <code>toDataURL</code>, which returns a base64 string of the image. However, when I do that, the image it renders is just a transparent rectangle with the dimensions of the chart, and it does not include the chart contents. </p>
  
  <p>Here is a fiddle: <a href="http://jsfiddle.net/KSgV7/" rel="noreferrer">http://jsfiddle.net/KSgV7/</a></p>
  
  <p>The "images" in the fiddle are styled with a black border, so you can see where they are supposed to be, since they seem to just be a big transparent block.</p>
  
  <p>Has anyone successfully converted a Chart.js chart to an image?</p>