Compute anchor value only once

src/ol/style/iconstyle.js

@@ -52,6 +52,12 @@ ol.style.Icon = function(opt_options) {
    */
   this.anchor_ = goog.isDef(options.anchor) ? options.anchor : [0.5, 0.5];
 
+  /**
+   * @private
+   * @type {Array.<number>}
+   */
+  this.normalizedAnchor_ = null;
+
   /**
    * @private
    * @type {ol.style.IconAnchorOrigin}
@@ -128,6 +134,9 @@ goog.inherits(ol.style.Icon, ol.style.Image);
  * @inheritDoc
  */
 ol.style.Icon.prototype.getAnchor = function() {
+  if (!goog.isNull(this.normalizedAnchor_)) {
+    return this.normalizedAnchor_;
+  }
   var anchor = this.anchor_;
   var size = this.getSize();
   if (this.anchorXUnits_ == ol.style.IconAnchorUnits.FRACTION ||
@@ -160,7 +169,8 @@ ol.style.Icon.prototype.getAnchor = function() {
       anchor[1] = -anchor[1] + size[1];
     }
   }
-  return anchor;
+  this.normalizedAnchor_ = anchor;
+  return this.normalizedAnchor_;
 };