Merge branch 'master' into utfgrid

lib/OpenLayers/Tile/Image.js

@@ -6,6 +6,7 @@
 
 /**
  * @requires OpenLayers/Tile.js
+ * @requires OpenLayers/Animation.js
  */
 
 /**
@@ -81,6 +82,23 @@ OpenLayers.Tile.Image = OpenLayers.Class(OpenLayers.Tile, {
      */
     maxGetUrlLength: null,
 
+    /**
+     * Property: canvasContext
+     * {CanvasRenderingContext2D} A canvas context associated with
+     * the tile image.
+     */
+    canvasContext: null,
+    
+    /**
+     * APIProperty: crossOriginKeyword
+     * The value of the crossorigin keyword to use when loading images. This is
+     * only relevant when using <getCanvasContext> for tiles from remote
+     * origins and should be set to either 'anonymous' or 'use-credentials'
+     * for servers that send Access-Control-Allow-Origin headers with their
+     * tiles.
+     */
+    crossOriginKeyword: null,
+
     /** TBD 3.0 - reorder the parameters to the init function to remove 
      *             URL. the getUrl() function on the layer gets called on 
      *             each draw(), so no need to specify it here.
@@ -203,6 +221,7 @@ OpenLayers.Tile.Image = OpenLayers.Class(OpenLayers.Tile, {
      * it can be reused in a new location.
      */
     clear: function() {
+        OpenLayers.Tile.prototype.clear.apply(this, arguments);
         var img = this.imgDiv;
         if (img) {
             OpenLayers.Event.stopObservingElement(img);
@@ -216,6 +235,7 @@ OpenLayers.Tile.Image = OpenLayers.Class(OpenLayers.Tile, {
             }
             OpenLayers.Element.removeClass(img, "olImageLoadError");
         }
+        this.canvasContext = null;
     },
     
     /**
@@ -297,6 +317,9 @@ OpenLayers.Tile.Image = OpenLayers.Class(OpenLayers.Tile, {
             } else {
                 OpenLayers.Event.observe(img, "load", load);
                 OpenLayers.Event.observe(img, "error", load);
+                if (img.crossOrigin) {
+                    img.crossOrigin = null;
+                }
                 img.src = this.blankImageUrl;
             }
         }
@@ -314,6 +337,10 @@ OpenLayers.Tile.Image = OpenLayers.Class(OpenLayers.Tile, {
         img.style.visibility = 'hidden';
         img.style.opacity = 0;
         if (url) {
+            // don't set crossOrigin if the url is a data URL
+            if (this.crossOriginKeyword && url.substr(0, 5 !== 'data:')) {
+                img.crossOrigin = this.crossOriginKeyword;
+            }
             img.src = url;
         }
     },
@@ -366,6 +393,7 @@ OpenLayers.Tile.Image = OpenLayers.Class(OpenLayers.Tile, {
         img.style.opacity = this.layer.opacity;
 
         this.isLoading = false;
+        this.canvasContext = null;
         this.events.triggerEvent("loadend");
 
         // IE<7 needs a reflow when the tiles are loaded because of the
@@ -406,6 +434,38 @@ OpenLayers.Tile.Image = OpenLayers.Class(OpenLayers.Tile, {
         }
     },
 
+    /**
+     * APIMethod: getCanvasContext
+     * Returns a canvas context associated with the tile image (with
+     * the image drawn on it).
+     * Returns undefined if the browser does not support canvas, if
+     * the tile has no image or if it's currently loading.
+     *
+     * The function returns a canvas context instance but the
+     * underlying canvas is still available in the 'canvas' property:
+     * (code)
+     * var context = tile.getCanvasContext();
+     * if (context) {
+     *     var data = context.canvas.toDataURL('image/jpeg');
+     * }
+     * (end)
+     *
+     * Returns:
+     * {Boolean}
+     */
+    getCanvasContext: function() {
+        if (OpenLayers.CANVAS_SUPPORTED && this.imgDiv && !this.isLoading) {
+            if (!this.canvasContext) {
+                var canvas = document.createElement("canvas");
+                canvas.width = this.size.w;
+                canvas.height = this.size.h;
+                this.canvasContext = canvas.getContext("2d");
+                this.canvasContext.drawImage(this.imgDiv, 0, 0);
+            }
+            return this.canvasContext;
+        }
+    },
+
     CLASS_NAME: "OpenLayers.Tile.Image"
 
 });