title: High resolution canvas of radar chart for pdf file
body: <p>I have the given code below for displaying a radar chart using Chart.js. When I display it as PDF on my screen it appears blurry. I've been trying to scale using webkitBackingStorePixelRatio and devicePixelRatio on Chrome, but I'm a little bit stuck.</p>
  
  <p>--HTML--</p>
  
  <pre><code>&lt;div class="chart"&gt;
      &lt;canvas id="myChart"&gt;&lt;/canvas&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>--Javascript--</p>
  
  <pre><code>&lt;script&gt;
  
          var ctx1 = document.getElementById("myChart");
  
          var myRadarChart1 = new Chart(ctx1, {
              type: 'radar',
              data: {
                  labels: {{ competenceCleTitle|json_encode|raw }},
                  datasets: [
                      {
                          backgroundColor: "#F79646",
                          borderColor: "#f59c1a",
                          pointBackgroundColor: "#f59c1a",
                          pointBorderColor: "#fff",
                          pointHoverBackgroundColor: "#fff",
                          pointHoverBorderColor: "#f59c1a",
                          pointRadius: 0,
                          data: {{ competenceCleNiveau|json_encode|raw }}
                      }
                  ]
              },
              options: {
                  legend: {
                      display: false
                  },
                  responsive: true,
                  scale: {
                      reverse: false,
                      ticks: {
                          display: false,
                          maxTicksLimit: 8,
                          stepSize: 1,
                          beginAtZero: true,
                          max: 5
                      }
                  }
              }
          });
  &lt;/script&gt;
  </code></pre>