perf: Add support for webgl pixelmaps.

This also adds a 2D texture lookup table.

This is a necessary antecedent to adding tiled pixelmaps.

src/canvas/pixelmapFeature.js

@@ -1,6 +1,8 @@
 var inherit = require('../inherit');
 var registerFeature = require('../registry').registerFeature;
 var pixelmapFeature = require('../pixelmapFeature');
+var geo_event = require('../event');
+var util = require('../util');
 
 /**
  * Create a new instance of class pixelmapFeature.
@@ -22,6 +24,191 @@ var canvas_pixelmapFeature = function (arg) {
   var object = require('./object');
   object.call(this);
 
+  var m_quadFeature,
+      s_exit = this._exit,
+      m_this = this;
+
+  /**
+   * If the specified coordinates are in the rendered quad, use the basis
+   * information from the quad to determine the pixelmap index value so that it
+   * can be included in the `found` results.
+   *
+   * @param {geo.geoPosition} geo Coordinate.
+   * @param {string|geo.transform|null} [gcs] Input gcs.  `undefined` to use
+   *    the interface gcs, `null` to use the map gcs, or any other transform.
+   * @returns {geo.feature.searchResult} An object with a list of features and
+   *    feature indices that are located at the specified point.
+   */
+  this.pointSearch = function (geo, gcs) {
+    if (m_quadFeature && m_this.m_info) {
+      var result = m_quadFeature.pointSearch(geo, gcs);
+      if (result.index.length === 1 && result.extra && result.extra[result.index[0]].basis) {
+        var basis = result.extra[result.index[0]].basis, x, y, idx;
+        x = Math.floor(basis.x * m_this.m_info.width);
+        y = Math.floor(basis.y * m_this.m_info.height);
+        if (x >= 0 && x < m_this.m_info.width &&
+            y >= 0 && y < m_this.m_info.height) {
+          idx = m_this.m_info.indices[y * m_this.m_info.width + x];
+          result = {
+            index: [idx],
+            found: [m_this.data()[idx]]
+          };
+          return result;
+        }
+      }
+    }
+    return {index: [], found: []};
+  };
+
+  /**
+   * Compute information for this pixelmap image.  It is wasteful to call this
+   * if the pixelmap has already been prepared (it is invalidated by a change
+   * in the image).
+   *
+   * @returns {geo.pixelmapFeature.info}
+   */
+  this._preparePixelmap = function () {
+    var i, idx, pixelData;
+
+    if (!util.isReadyImage(m_this.m_srcImage)) {
+      return;
+    }
+    m_this.m_info = {
+      width: m_this.m_srcImage.naturalWidth,
+      height: m_this.m_srcImage.naturalHeight,
+      canvas: document.createElement('canvas')
+    };
+
+    m_this.m_info.canvas.width = m_this.m_info.width;
+    m_this.m_info.canvas.height = m_this.m_info.height;
+    m_this.m_info.context = m_this.m_info.canvas.getContext('2d');
+
+    m_this.m_info.context.drawImage(m_this.m_srcImage, 0, 0);
+    m_this.m_info.imageData = m_this.m_info.context.getImageData(
+      0, 0, m_this.m_info.canvas.width, m_this.m_info.canvas.height);
+    pixelData = m_this.m_info.imageData.data;
+    m_this.m_info.indices = new Array(pixelData.length / 4);
+    m_this.m_info.area = pixelData.length / 4;
+
+    m_this.m_info.mappedColors = {};
+    for (i = 0; i < pixelData.length; i += 4) {
+      idx = pixelData[i] + (pixelData[i + 1] << 8) + (pixelData[i + 2] << 16);
+      m_this.m_info.indices[i / 4] = idx;
+      if (!m_this.m_info.mappedColors[idx]) {
+        m_this.m_info.mappedColors[idx] = {first: i / 4};
+      }
+      m_this.m_info.mappedColors[idx].last = i / 4;
+    }
+    return m_this.m_info;
+  };
+
+  /**
+   * Given the loaded pixelmap image, create a canvas the size of the image.
+   * Compute a color for each distinct index and recolor the canvas based on
+   * these colors, then draw the resultant image as a quad.
+   *
+   * @fires geo.event.pixelmap.prepared
+   */
+  this._computePixelmap = function () {
+    var data = m_this.data() || [],
+        colorFunc = m_this.style.get('color'),
+        i, idx, lastidx, color, pixelData, indices, mappedColors,
+        updateFirst, updateLast = -1, update, prepared;
+
+    if (!m_this.m_info) {
+      if (!m_this._preparePixelmap()) {
+        return;
+      }
+      prepared = true;
+    }
+    mappedColors = m_this.m_info.mappedColors;
+    updateFirst = m_this.m_info.area;
+    for (idx in mappedColors) {
+      if (mappedColors.hasOwnProperty(idx)) {
+        color = colorFunc(data[idx], +idx) || {};
+        color = [
+          (color.r || 0) * 255,
+          (color.g || 0) * 255,
+          (color.b || 0) * 255,
+          color.a === undefined ? 255 : (color.a * 255)
+        ];
+        mappedColors[idx].update = (
+          !mappedColors[idx].color ||
+          mappedColors[idx].color[0] !== color[0] ||
+          mappedColors[idx].color[1] !== color[1] ||
+          mappedColors[idx].color[2] !== color[2] ||
+          mappedColors[idx].color[3] !== color[3]);
+        if (mappedColors[idx].update) {
+          mappedColors[idx].color = color;
+          updateFirst = Math.min(mappedColors[idx].first, updateFirst);
+          updateLast = Math.max(mappedColors[idx].last, updateLast);
+        }
+      }
+    }
+    /* If nothing was updated, we are done */
+    if (updateFirst >= updateLast) {
+      return;
+    }
+    /* Update only the extent that has changed */
+    pixelData = m_this.m_info.imageData.data;
+    indices = m_this.m_info.indices;
+    for (i = updateFirst; i <= updateLast; i += 1) {
+      idx = indices[i];
+      if (idx !== lastidx) {
+        lastidx = idx;
+        color = mappedColors[idx].color;
+        update = mappedColors[idx].update;
+      }
+      if (update) {
+        pixelData[i * 4] = color[0];
+        pixelData[i * 4 + 1] = color[1];
+        pixelData[i * 4 + 2] = color[2];
+        pixelData[i * 4 + 3] = color[3];
+      }
+    }
+    /* Place the updated area into the canvas */
+    m_this.m_info.context.putImageData(
+      m_this.m_info.imageData, 0, 0, 0, Math.floor(updateFirst / m_this.m_info.width),
+      m_this.m_info.width, Math.ceil((updateLast + 1) / m_this.m_info.width));
+
+    /* If we haven't made a quad feature, make one now.  The quad feature needs
+     * to have the canvas capability. */
+    if (!m_quadFeature) {
+      m_quadFeature = m_this.layer().createFeature('quad', {
+        selectionAPI: false,
+        gcs: m_this.gcs(),
+        visible: m_this.visible(undefined, true)
+      });
+      m_this.dependentFeatures([m_quadFeature]);
+      m_quadFeature.style({
+        image: m_this.m_info.canvas,
+        position: m_this.style.get('position')})
+      .data([{}])
+      .draw();
+    }
+    /* If we prepared the pixelmap and rendered it, send a prepared event */
+    if (prepared) {
+      m_this.geoTrigger(geo_event.pixelmap.prepared, {
+        pixelmap: m_this
+      });
+    }
+  };
+
+  /**
+   * Destroy.  Deletes the associated quadFeature.
+   *
+   * @returns {this}
+   */
+  this._exit = function () {
+    if (m_quadFeature && m_this.layer()) {
+      m_this.layer().deleteFeature(m_quadFeature);
+      m_quadFeature = null;
+      m_this.dependentFeatures([]);
+    }
+    s_exit();
+    return m_this;
+  };
+
   this._init(arg);
   return this;
 };