fast.html

<!doctype html>

<html>
<head>
  <meta charset="utf-8">
  <title>tracking.js - feature detection</title>
  <link rel="stylesheet" href="assets/demo.css">

  <script src="../build/tracking-min.js"></script>
   <script src="../node_modules/dat.gui/build/dat.gui.min.js"></script>

  <style>
  .demo-container {
    background: #131112;
  }
  #image {
    position: absolute;
    left: -1000px;
    top: -1000px;
  }
  #canvas {
    position: absolute;
    left: 50%;
    top: 50%;
    margin: -200px 0 0 -200px;
  }
  </style>
</head>
<body>
  <div class="demo-title">
    <p><a href="http://trackingjs.com" target="_parent">tracking.js</a> － detect feature points on a image</p>
  </div>

  <div class="demo-frame">
    <div class="demo-container">
      <img id="image" src="assets/fast.png" />
      <canvas id="canvas" width="400" height="400"></canvas>
    </div>
  </div>

  <script>
    window.onload = function() {
      var width = 400;
      var height = 400;
      var canvas = document.getElementById('canvas');
      var context = canvas.getContext('2d');

      var image = document.getElementById('image');

      window.fastThreshold = 10;

      var doFindFeatures = function() {
        tracking.Fast.THRESHOLD = window.fastThreshold;
        context.drawImage(image, 0, 0, width, height);

        var imageData = context.getImageData(0, 0, width, height);
        var gray = tracking.Image.grayscale(imageData.data, width, height);
        var corners = tracking.Fast.findCorners(gray, width, height);

        for (var i = 0; i < corners.length; i += 2) {
          context.fillStyle = '#f00';
          context.fillRect(corners[i], corners[i + 1], 3, 3);
        }
      };

      doFindFeatures();

      var gui = new dat.GUI();
      gui.add(window, 'fastThreshold', 0, 100).onChange(doFindFeatures);
    }
  </script>
</body>
</html>