Pass data object to operations

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);