Image source refactoring

src/ol/source/imagecanvassource.js

@@ -0,0 +1,76 @@
+goog.provide('ol.source.ImageCanvas');
+
+goog.require('ol.CanvasFunctionType');
+goog.require('ol.ImageCanvas');
+goog.require('ol.extent');
+goog.require('ol.source.Image');
+
+
+
+/**
+ * @constructor
+ * @extends {ol.source.Image}
+ * @param {olx.source.ImageCanvasOptions} options
+ */
+ol.source.ImageCanvas = function(options) {
+  goog.base(this, {
+    attributions: options.attributions,
+    extent: options.extent,
+    logo: options.logo,
+    projection: options.projection,
+    resolutions: options.resolutions
+  });
+
+  /**
+   * @private
+   * @type {ol.CanvasFunctionType}
+   */
+  this.canvasFunction_ = options.canvasFunction;
+
+  /**
+   * @private
+   * @type {ol.ImageCanvas}
+   */
+  this.canvas_ = null;
+
+  /**
+   * @private
+   * @type {number}
+   */
+  this.ratio_ = goog.isDef(options.ratio) ?
+      options.ratio : 1.5;
+
+};
+goog.inherits(ol.source.ImageCanvas, ol.source.Image);
+
+
+/**
+ * @inheritDoc
+ */
+ol.source.ImageCanvas.prototype.getImage =
+    function(extent, resolution, pixelRatio, projection) {
+  resolution = this.findNearestResolution(resolution);
+
+  var canvas = this.canvas_;
+  if (!goog.isNull(canvas) &&
+      canvas.getResolution() == resolution &&
+      canvas.getPixelRatio() == pixelRatio &&
+      ol.extent.containsExtent(canvas.getExtent(), extent)) {
+    return canvas;
+  }
+
+  extent = extent.slice();
+  ol.extent.scaleFromCenter(extent, this.ratio_);
+  var width = (extent[2] - extent[0]) / resolution;
+  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);
+  this.canvas_ = canvas;
+
+  return canvas;
+
+};