Canvas heatmap

examples/heatmap/example.json

@@ -0,0 +1,9 @@
+{
+  "path": "heatmap",
+  "title": "Heatmap Feature",
+  "exampleCss": ["main.css"],
+  "exampleJs": ["main.js"],
+  "about": {
+    "text": "This example shows how to add a heatmap to a map."
+  }
+}

examples/heatmap/index.jade

@@ -0,0 +1 @@
+extends ../common/templates/index.jade

examples/heatmap/main.js

@@ -0,0 +1,49 @@
+// Run after the DOM loads
+$(function () {
+  'use strict';
+
+  var map = geo.map({
+    node: '#map',
+    center: {
+      x: -98,
+      y: 39
+    },
+    zoom: 3
+  });
+
+  $.ajax('https://s3.amazonaws.com/uploads.hipchat.com/446632/3114847/4dZfl0YfZpTfYzq/AdderallCities2015.csv', {
+    success: function (resp) {
+      var rows = resp.split(/\r\n|\n|\r/);
+      rows = rows.map( function (r) {
+        var fields = r.split(',');
+        return [fields[12], fields[24], fields[25]].map(parseFloat);
+      });
+      rows.splice(0, 1);
+
+      var layer = map.createLayer('feature', {renderer: 'canvas'});
+      var heatmap = layer.createFeature('heatmap')
+                      .data(rows)
+                      .intensity(function (d) {
+                        return d[0];
+                      })
+                      .position(function (d) {
+                        return {
+                          x: d[2],
+                          y: d[1]
+                        };
+                      })
+                      .style('radius', 10)
+                      .style('blurRadius', 30)
+                      .style('opacity', 1.0)
+                      .style('color',
+                        {0:    {r: 0, g: 0, b: 0, a: 0.0},
+                         0.25: {r: 0, g: 1, b: 0, a: 0.5},
+                         0.5:  {r: 1, g: 1, b: 0, a: 0.8},
+                         1:    {r: 1, g: 0, b: 0, a: 1.0}});
+      map.draw();
+    }
+  });
+
+  var base = map.createLayer('osm');
+  map.draw();
+});

sources.json

@@ -41,7 +41,8 @@
         "renderer.js",
         "osmLayer.js",
         "domRenderer.js",
-        "choroplethFeature.js"
+        "choroplethFeature.js",
+        "heatmapFeature.js"
       ]
     },
     "geo.util": {
@@ -77,7 +78,8 @@
         "init.js",
         "quadFeature.js",
         "canvasRenderer.js",
-        "tileLayer.js"
+        "tileLayer.js",
+        "heatmapFeature.js"
       ]
     },
     "geo.d3": {

src/canvas/heatmapFeature.js

@@ -0,0 +1,207 @@
+var inherit = require('../inherit');
+var registerFeature = require('../registry').registerFeature;
+var heatmapFeature = require('../heatmapFeature');
+
+//////////////////////////////////////////////////////////////////////////////
+/**
+ * Create a new instance of class heatmapFeature
+ * Inspired from
+ *    https://github.com/mourner/simpleheat/blob/gh-pages/simpleheat.js
+ *
+ * @class
+ * @param {Object} arg Options object
+ * @extends geo.heatmapFeature
+ * @returns {canvas_heatmapFeature}
+ */
+//////////////////////////////////////////////////////////////////////////////
+var canvas_heatmapFeature = function (arg) {
+  'use strict';
+
+  if (!(this instanceof canvas_heatmapFeature)) {
+    return new canvas_heatmapFeature(arg);
+  }
+  heatmapFeature.call(this, arg);
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * @private
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  var m_this = this,
+      s_exit = this._exit,
+      s_init = this._init,
+      s_update = this._update;
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * Meta functions for converting from geojs styles to canvas.
+   * @private
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  this._convertColor = function (c) {
+    var color;
+    if (c.hasOwnProperty('r') &&
+      c.hasOwnProperty('g') &&
+      c.hasOwnProperty('b') &&
+      c.hasOwnProperty('a')) {
+      color = 'rgba(' + 255 * c.r + ',' + 255 * c.g + ','
+                    + 255 * c.b + ',' + c.a + ')';
+    }
+    return color;
+  };
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * Compute gradient (color lookup table)
+   * @protected
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  this._computeGradient = function () {
+    var canvas, stop, context2d, gradient, colors;
+
+    if (!m_this._grad) {
+      canvas = document.createElement('canvas');
+      context2d = canvas.getContext('2d');
+      gradient = context2d.createLinearGradient(0, 0, 0, 256);
+      colors = m_this.style('color');
+
+      canvas.width = 1;
+      canvas.height = 256;
+
+      for (stop in colors) {
+        gradient.addColorStop(stop, m_this._convertColor(colors[stop]));
+      }
+
+      context2d.fillStyle = gradient;
+      context2d.fillRect(0, 0, 1, 256);
+      m_this._grad = context2d.getImageData(0, 0, 1, 256).data;
+    }
+
+    return m_this;
+  };
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * Create circle for each data point
+   * @protected
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  this._createCircle = function () {
+    var circle, ctx, r, r2, blur;
+    if (!m_this._circle) {
+      circle = m_this._circle = document.createElement('canvas');
+      ctx = circle.getContext('2d');
+      r = m_this.style('radius');
+      blur = m_this.style('blurRadius');
+
+      r2 = blur + r;
+
+      circle.width = circle.height = r2 * 2;
+      ctx.shadowOffsetX = ctx.shadowOffsetY = r2 * 2;
+      ctx.shadowBlur = blur;
+      ctx.shadowColor = 'black';
+
+      ctx.beginPath();
+      ctx.arc(-r2, -r2, r, 0, Math.PI * 2, true);
+      ctx.closePath();
+      ctx.fill();
+      m_this._circle = circle;
+    }
+    return m_this;
+  };
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * Compute color for each pixel on the screen
+   * @protected
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  this._colorize = function (pixels, gradient) {
+    var i, j;
+    for (i = 0; i < pixels.length; i += 4) {
+      // Get opacity from the temporary canvas image,
+      // then multiply by 4 to get the color index on linear gradient
+      j = pixels[i + 3] * 4;
+      if (j) {
+        pixels[i] = gradient[j];
+        pixels[i + 1] = gradient[j + 1];
+        pixels[i + 2] = gradient[j + 2];
+        pixels[i + 3] = m_this.style('opacity') * gradient[j + 3];
+      }
+    }
+  };
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * Render each data point on canvas
+   * @protected
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  this._renderOnCanvas = function (context2d, map) {
+    var data = m_this.data() || [],
+        radius = m_this.style('radius') + m_this.style('blurRadius'),
+        pos, intensity, canvas, pixelArray;
+    m_this._createCircle();
+    m_this._computeGradient();
+    data.forEach(function (d) {
+      pos = m_this.layer().map().gcsToDisplay(m_this.position()(d));
+      intensity = (m_this.intensity()(d) - m_this.minIntensity()) /
+                  (m_this.maxIntensity() - m_this.minIntensity());
+      // Small values are not visible because globalAlpha < .01
+      // cannot be read from imageData
+      context2d.globalAlpha = intensity < 0.01 ? 0.01 : intensity;
+      context2d.drawImage(m_this._circle, pos.x - radius, pos.y - radius);
+    });
+    canvas = m_this.layer().canvas()[0];
+    pixelArray = context2d.getImageData(0, 0, canvas.width, canvas.height);
+    m_this._colorize(pixelArray.data, m_this._grad);
+    context2d.putImageData(pixelArray, 0, 0);
+    return m_this;
+  };
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * Initialize
+   * @protected
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  this._init = function () {
+    s_init.call(m_this, arg);
+    return m_this;
+  };
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * Update
+   * @protected
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  this._update = function () {
+    s_update.call(m_this);
+    if (m_this.buildTime().getMTime() <= m_this.dataTime().getMTime() ||
+        m_this.updateTime().getMTime() < m_this.getMTime()) {
+      m_this._build();
+    }
+    m_this.updateTime().modified();
+    return m_this;
+  };
+
+  ////////////////////////////////////////////////////////////////////////////
+  /**
+   * Destroy
+   * @protected
+   */
+  ////////////////////////////////////////////////////////////////////////////
+  this._exit = function () {
+    s_exit.call(m_this);
+  };
+
+  m_this._init(arg);
+  return this;
+};
+
+inherit(canvas_heatmapFeature, heatmapFeature);
+
+// Now register it
+registerFeature('canvas', 'heatmap', canvas_heatmapFeature);
+module.exports = canvas_heatmapFeature;

src/canvas/index.js

@@ -4,5 +4,6 @@
 module.exports = {
   canvasRenderer: require('./canvasRenderer'),
   quadFeature: require('./quadFeature'),
+  heatmapFeature: require('./heatmapFeature'),
   tileLayer: require('./tileLayer')
 };