title: unable to add background color to the canvas using jspdf and chartjs
body: <p>I am exporting a bar chart to pdf by using jspdf plugin. The bars on the chart is in white color so when I export to pdf ( as a png image) , the bars are not visible on the transparent background in the pdf. I added a gray background color on the container so that the white bars are clearly visible. When I export the graph to pdf, it still shows the transparent background not the gray color. Can someone tell me what i am missing?</p>
  
  <p>javascript:</p>
  
  <pre><code>    $(document).ready(function(){
  
      $('#hyppdf').click(function(){
      var canvasImg = document.getElementById("myChart").toDataURL("image/png",     
      1.0);
      var doc = new jsPDF();
      doc.setFontSize(33);
      doc.setFillColor(135, 124,45,0);
      doc.addImage(canvasImg, 'png', 10, 10, 150, 100);
      doc.save('sample.pdf');
      })
  
      var ctx = document.getElementById("myChart").getContext('2d');
  
    var myChart = new Chart(ctx, {
    type: 'bar',
    data: {
      labels: ["M", "T", "W", "T", "F", "S", "S"],
      datasets: [{
        label: 'apples',
        data: [12, 19, 3, 17, 28, 24, 7],
        backgroundColor: "rgba(255,255,255,1)"
      }, {
        label: 'oranges',
        data: [30, 29, 5, 5, 20, 3, 10],
        backgroundColor: "rgba(255,153,0,1)"
      }]
    }
  });
  
  })
  </code></pre>
  
  <p>html:</p>
  
  <pre><code>    &lt;div class="container" style="background-color:#ccc"&gt;
    &lt;h2&gt; &lt;a id="hyppdf" href="#"&gt;download&lt;/a&gt;&lt;/h2&gt;
    &lt;div&gt;
      &lt;canvas id="myChart"&gt;&lt;/canvas&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p><a href="https://jsfiddle.net/2gnajnz4/5/" rel="nofollow noreferrer">https://jsfiddle.net/2gnajnz4/5/</a></p>
  
  <p>Thanks</p>