title: Why are symbols rendered three times in a flot graphic?
body: <p>I am using the flot library to render a plot where PNG images are rendered as points. It's working, but each PNG image seems to be rendered three times. This is visible on a refresh (the overlap isn't perfect), and I also logged the image's onload function and Firebug tells me that it is being called three times for each graphic. Here is the function that renders the images (counter is the logging variable):</p>
  
  <pre><code>function generateImageFunction (image) {
      return function getImage(ctx, x, y, radius, shadow) {                   
          var img = new Image();
          img.onload = function() {
              console.log(counter++);
              ctx.drawImage(img, x, y, img.width, img.height);    
          }
          img.src = image;
      }
  }
  </code></pre>
  
  <p>data has 13 series, these are just the first two as an example:</p>
  
  <pre><code>var data = [
              { 
               data: [[1, 1]], 
               points: { symbol: generateImageFunction("face-angel.png") }
              }
              { 
               data: [[2, 2]], 
               points: { symbol: generateImageFunction("face-angry.png") }
              }
             ];
  </code></pre>
  
  <p>My options are these:</p>
  
  <pre><code>var options = {
                 series: {
                     points: { show: true },
                 },
                 xaxis: { min: 0, max: 15},
                 yaxis: { show: false, min: 0, max: 15 },
                 selection: { mode: "x" }
  };
  </code></pre>
  
  <p>And then I do <code>$.plot($("#placeholder"), data, options);</code></p>
  
  <p>With the 13 data series, the counter variable goes to 39 when I first load the page. If I zoom in on a region with only one data point, the counter is increased by 3. Can anyone tell me why this is happening, or what can I do investigate further?</p>