Pass data object to operations

examples/raster.js

@@ -7,7 +7,7 @@ goog.require('ol.layer.Tile');
 goog.require('ol.source.BingMaps');
 goog.require('ol.source.Raster');
 
-function tgi(pixels) {
+function tgi(pixels, data) {
   var pixel = pixels[0];
   var r = pixel[0] / 255;
   var g = pixel[1] / 255;
@@ -17,20 +17,17 @@ function tgi(pixels) {
   return pixels;
 }
 
-var counts = new Counts(0, 25);
 
-function summarize(pixels) {
+function summarize(pixels, data) {
   var value = pixels[0][0];
-  counts.increment(value);
+  data.counts.increment(value);
   return pixels;
 }
 
-var threshold = 10;
-
-function color(pixels) {
+function color(pixels, data) {
   var pixel = pixels[0];
   var value = pixel[0];
-  if (value > threshold) {
+  if (value > data.threshold) {
     pixel[0] = 0;
     pixel[1] = 255;
     pixel[2] = 0;
@@ -51,12 +48,17 @@ var raster = new ol.source.Raster({
   operations: [tgi, summarize, color]
 });
 
-raster.on('beforeoperations', function() {
+var counts = new Counts(0, 25);
+var threshold = 10;
+
+raster.on('beforeoperations', function(event) {
   counts.clear();
+  event.data.counts = counts;
+  event.data.threshold = threshold;
 });
 
 raster.on('afteroperations', function(event) {
-  schedulePlot(event.resolution);
+  schedulePlot(event.resolution, event.data.counts);
 });
 
 var map = new ol.Map({
@@ -114,12 +116,12 @@ Counts.prototype.increment = function(value) {
 };
 
 var timer = null;
-function schedulePlot(resolution) {
+function schedulePlot(resolution, counts) {
   if (timer) {
     clearTimeout(timer);
     timer = null;
   }
-  timer = setTimeout(plot.bind(null, resolution), 1000 / 60);
+  timer = setTimeout(plot.bind(null, resolution, counts), 1000 / 60);
 }
 
 var barWidth = 15;
@@ -133,7 +135,7 @@ var chartRect = chart[0][0].getBoundingClientRect();
 var tip = d3.select(document.body).append('div')
     .attr('class', 'tip');
 
-function plot(resolution) {
+function plot(resolution, counts) {
   var yScale = d3.scale.linear()
       .domain([0, d3.max(counts.values)])
       .range([0, plotHeight]);

externs/oli.js

@@ -284,6 +284,12 @@ oli.source.RasterEvent.prototype.extent;
 oli.source.RasterEvent.prototype.resolution;
 
 
+/**
+ * @type {Object}
+ */
+oli.source.RasterEvent.prototype.data;
+
+
 /**
  * @interface
  */

src/ol/raster/operation.js

@@ -21,9 +21,12 @@ ol.raster.OperationType = {
  * return an array of the same.  For `'image'` type operations, functions will
  * be called with an array of {@link ImageData
  * https://developer.mozilla.org/en-US/docs/Web/API/ImageData} and should return
- * an array of the same.
+ * an array of the same.  The operations are called with a second "data"
+ * argument, which can be used for storage.  The data object is accessible
+ * from raster events, where it can be initialized in "beforeoperations" and
+ * accessed again in "afteroperations."
  *
- * @typedef {function((Array.<ol.raster.Pixel>|Array.<ImageData>)):
+ * @typedef {function((Array.<ol.raster.Pixel>|Array.<ImageData>), Object):
  *     (Array.<ol.raster.Pixel>|Array.<ImageData>)}
  * @api
  */

src/ol/source/rastersource.js

@@ -223,8 +223,9 @@ ol.source.Raster.prototype.composeFrame_ = function(frameState) {
         this.renderers_[i], frameState, frameState.layerStatesArray[i]);
   }
 
+  var data = {};
   this.dispatchEvent(new ol.source.RasterEvent(
-      ol.source.RasterEventType.BEFOREOPERATIONS, frameState));
+      ol.source.RasterEventType.BEFOREOPERATIONS, frameState, data));
 
   var targetImageData = null;
   if (this.operationType_ === ol.raster.OperationType.PIXEL) {
@@ -242,20 +243,20 @@ ol.source.Raster.prototype.composeFrame_ = function(frameState) {
         pixel[2] = source[j + 2];
         pixel[3] = source[j + 3];
       }
-      pixel = this.runPixelOperations_(pixels)[0];
+      pixel = this.runPixelOperations_(pixels, data)[0];
       target[j] = pixel[0];
       target[j + 1] = pixel[1];
       target[j + 2] = pixel[2];
       target[j + 3] = pixel[3];
     }
   } else if (this.operationType_ === ol.raster.OperationType.IMAGE) {
-    targetImageData = this.runImageOperations_(imageDatas)[0];
+    targetImageData = this.runImageOperations_(imageDatas, data)[0];
   } else {
     goog.asserts.fail('unsupported operation type: ' + this.operationType_);
   }
 
   this.dispatchEvent(new ol.source.RasterEvent(
-      ol.source.RasterEventType.AFTEROPERATIONS, frameState));
+      ol.source.RasterEventType.AFTEROPERATIONS, frameState, data));
 
   context.putImageData(targetImageData, 0, 0);
 
@@ -266,12 +267,13 @@ ol.source.Raster.prototype.composeFrame_ = function(frameState) {
 /**
  * Run pixel-wise operations to transform pixels.
  * @param {Array.<ol.raster.Pixel>} pixels The input pixels.
+ * @param {Object} data User storage.
  * @return {Array.<ol.raster.Pixel>} The modified pixels.
  * @private
  */
-ol.source.Raster.prototype.runPixelOperations_ = function(pixels) {
+ol.source.Raster.prototype.runPixelOperations_ = function(pixels, data) {
   for (var i = 0, ii = this.operations_.length; i < ii; ++i) {
-    pixels = this.operations_[i](pixels);
+    pixels = this.operations_[i](pixels, data);
   }
   return pixels;
 };
@@ -280,12 +282,13 @@ ol.source.Raster.prototype.runPixelOperations_ = function(pixels) {
 /**
  * Run image operations.
  * @param {Array.<ImageData>} imageDatas The input image data.
+ * @param {Object} data User storage.
  * @return {Array.<ImageData>} The output image data.
  * @private
  */
-ol.source.Raster.prototype.runImageOperations_ = function(imageDatas) {
+ol.source.Raster.prototype.runImageOperations_ = function(imageDatas, data) {
   for (var i = 0, ii = this.operations_.length; i < ii; ++i) {
-    imageDatas = this.operations_[i](imageDatas);
+    imageDatas = this.operations_[i](imageDatas, data);
   }
   return imageDatas;
 };
@@ -396,8 +399,9 @@ ol.source.Raster.createTileRenderer_ = function(source) {
  * @implements {oli.source.RasterEvent}
  * @param {string} type Type.
  * @param {olx.FrameState} frameState The frame state.
+ * @param {Object} data An object made available to operations.
  */
-ol.source.RasterEvent = function(type, frameState) {
+ol.source.RasterEvent = function(type, frameState, data) {
   goog.base(this, type);
 
   /**
@@ -414,6 +418,14 @@ ol.source.RasterEvent = function(type, frameState) {
    */
   this.resolution = frameState.viewState.resolution / frameState.pixelRatio;
 
+  /**
+   * An object made available to all operations.  This can be used by operations
+   * as a storage object (e.g. for calculating statistics).
+   * @type {Object}
+   * @api
+   */
+  this.data = data;
+
 };
 goog.inherits(ol.source.RasterEvent, goog.events.Event);