Give ol.Image an imageLoadFunction argument

src/ol/image.js

@@ -20,9 +20,10 @@ goog.require('ol.extent');
  * @param {Array.<ol.Attribution>} attributions Attributions.
  * @param {string} src Image source URI.
  * @param {?string} crossOrigin Cross origin.
+ * @param {ol.ImageLoadFunctionType} imageLoadFunction Image load function.
  */
-ol.Image =
+ol.Image = function(extent, resolution, pixelRatio, attributions, src,
-    function(extent, resolution, pixelRatio, attributions, src, crossOrigin) {
+    crossOrigin, imageLoadFunction) {
 
   goog.base(this, extent, resolution, pixelRatio, ol.ImageState.IDLE,
       attributions);
@@ -59,6 +60,13 @@ ol.Image =
    * @type {ol.ImageState}
    */
   this.state = ol.ImageState.IDLE;
+
+  /**
+   * @private
+   * @type {ol.ImageLoadFunctionType}
+   */
+  this.imageLoadFunction_ = imageLoadFunction;
+
 };
 goog.inherits(ol.Image, ol.ImageBase);
 
@@ -127,7 +135,7 @@ ol.Image.prototype.load = function() {
       goog.events.listenOnce(this.image_, goog.events.EventType.LOAD,
           this.handleImageLoad_, false, this)
     ];
-    this.image_.src = this.src_;
+    this.imageLoadFunction_(this, this.src_);
   }
 };
 

src/ol/imageloadfunction.js

@@ -0,0 +1,21 @@
+goog.provide('ol.ImageLoadFunctionType');
+
+
+/**
+ * A function that takes an {@link ol.Image} for the image and a `{string}` for
+ * the src as arguments. It is supposed to make it so the underlying image
+ * {@link ol.Image#getImage} is assigned the content specified by the src. If
+ * not specified, the default is
+ *
+ *     function(image, src) {
+ *       image.getImage().src = src;
+ *     }
+ *
+ * Providing a custom `imageLoadFunction` can be useful to load images with
+ * post requests or - in general - through XHR requests, where the src of the
+ * image element would be set to a data URI when the content is loaded.
+ *
+ * @typedef {function(ol.Image, string)}
+ * @api
+ */
+ol.ImageLoadFunctionType;