Merge pull request #4083 from tschaub/missing-description

Add API descriptions.

src/ol/style/imagestyle.js

@@ -119,6 +119,8 @@ ol.style.Image.prototype.getSnapToPixel = function() {
 
 
 /**
+ * Get the anchor point.  The anchor determines the center point for the
+ * symbolizer.  Its units are determined by `anchorXUnits` and `anchorYUnits`.
  * @function
  * @return {Array.<number>} Anchor.
  */
@@ -126,6 +128,7 @@ ol.style.Image.prototype.getAnchor = goog.abstractMethod;
 
 
 /**
+ * Get the image element for the symbolizer.
  * @function
  * @param {number} pixelRatio Pixel ratio.
  * @return {HTMLCanvasElement|HTMLVideoElement|Image} Image element.
@@ -159,6 +162,7 @@ ol.style.Image.prototype.getHitDetectionImageSize = goog.abstractMethod;
 
 
 /**
+ * Get the origin of the symbolizer.
  * @function
  * @return {Array.<number>} Origin.
  */
@@ -166,6 +170,7 @@ ol.style.Image.prototype.getOrigin = goog.abstractMethod;
 
 
 /**
+ * Get the size of the symbolizer (in pixels).
  * @function
  * @return {ol.Size} Size.
  */