Pass pixelRatio to canvasFunction

examples/d3.js

@@ -38,11 +38,13 @@ d3.json('data/us.json', function(error, us) {
    * This function uses d3 to render the topojson features to a canvas.
    * @param {ol.Extent} extent Extent.
    * @param {number} resolution Resolution.
+   * @param {number} pixelRatio Pixel ratio.
    * @param {ol.Size} size Size.
    * @param {ol.proj.Projection} projection Projection.
    * @return {HTMLCanvasElement}
    */
-  var canvasFunction = function(extent, resolution, size, projection) {
+  var canvasFunction = function(extent, resolution, pixelRatio,
+      size, projection) {
     var canvasWidth = size[0];
     var canvasHeight = size[1];
 

src/ol/canvasfunction.js

@@ -2,7 +2,7 @@ goog.provide('ol.CanvasFunctionType');
 
 
 /**
- * @typedef {function(this:ol.source.ImageCanvas, ol.Extent, number, ol.Size,
- *     ol.proj.Projection): HTMLCanvasElement}
+ * @typedef {function(this:ol.source.ImageCanvas, ol.Extent, number,
+ *     number, ol.Size, ol.proj.Projection): HTMLCanvasElement}
  */
 ol.CanvasFunctionType;

src/ol/source/imagecanvassource.js

@@ -65,12 +65,13 @@ ol.source.ImageCanvas.prototype.getImage =
   var height = (extent[3] - extent[1]) / resolution;
   var size = [width * pixelRatio, height * pixelRatio];
 
-  var canvasElement = this.canvasFunction_(extent, resolution, size,
-      projection);
-  canvas = new ol.ImageCanvas(extent, resolution, pixelRatio,
-      this.getAttributions(), canvasElement);
+  var canvasElement = this.canvasFunction_(
+      extent, resolution, pixelRatio, size, projection);
+  if (!goog.isNull(canvasElement)) {
+    canvas = new ol.ImageCanvas(extent, resolution, pixelRatio,
+        this.getAttributions(), canvasElement);
+  }
   this.canvas_ = canvas;
 
   return canvas;
-
 };