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/* Copyright (c) 2006-2013 by OpenLayers Contributors (see authors.txt for
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* full list of contributors). Published under the 2-clause BSD license.
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* See license.txt in the OpenLayers distribution or repository for the
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* full text of the license. */
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/**
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* @requires OpenLayers/Layer.js
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* @requires OpenLayers/Tile/Image.js
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*/
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/**
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* Class: OpenLayers.Layer.Image
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* Instances of OpenLayers.Layer.Image are used to display data from a web
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* accessible image as a map layer. Create a new image layer with the
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* <OpenLayers.Layer.Image> constructor.
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*
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* Inherits from:
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* - <OpenLayers.Layer>
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*/
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OpenLayers.Layer.Image = OpenLayers.Class(OpenLayers.Layer, {
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/**
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* Property: isBaseLayer
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* {Boolean} The layer is a base layer. Default is true. Set this property
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* in the layer options
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*/
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isBaseLayer: true,
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/**
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* Property: url
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* {String} URL of the image to use
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*/
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url: null,
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/**
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* Property: extent
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* {<OpenLayers.Bounds>} The image bounds in map units. This extent will
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* also be used as the default maxExtent for the layer. If you wish
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* to have a maxExtent that is different than the image extent, set the
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* maxExtent property of the options argument (as with any other layer).
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*/
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extent: null,
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/**
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* Property: size
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* {<OpenLayers.Size>} The image size in pixels
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*/
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size: null,
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/**
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* Property: tile
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* {<OpenLayers.Tile.Image>}
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*/
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tile: null,
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/**
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* Property: aspectRatio
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* {Float} The ratio of height/width represented by a single pixel in the
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* graphic
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*/
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aspectRatio: null,
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/**
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* Constructor: OpenLayers.Layer.Image
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* Create a new image layer
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*
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* Parameters:
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* name - {String} A name for the layer.
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* url - {String} Relative or absolute path to the image
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* extent - {<OpenLayers.Bounds>} The extent represented by the image
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* size - {<OpenLayers.Size>} The size (in pixels) of the image
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* options - {Object} Hashtable of extra options to tag onto the layer
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*/
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initialize: function(name, url, extent, size, options) {
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this.url = url;
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this.extent = extent;
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this.maxExtent = extent;
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this.size = size;
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OpenLayers.Layer.prototype.initialize.apply(this, [name, options]);
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this.aspectRatio = (this.extent.getHeight() / this.size.h) /
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(this.extent.getWidth() / this.size.w);
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},
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/**
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* Method: destroy
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* Destroy this layer
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*/
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destroy: function() {
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if (this.tile) {
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this.removeTileMonitoringHooks(this.tile);
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this.tile.destroy();
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this.tile = null;
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}
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OpenLayers.Layer.prototype.destroy.apply(this, arguments);
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},
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/**
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* Method: clone
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* Create a clone of this layer
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*
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* Paramters:
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* obj - {Object} An optional layer (is this ever used?)
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*
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* Returns:
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* {<OpenLayers.Layer.Image>} An exact copy of this layer
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*/
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clone: function(obj) {
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if(obj == null) {
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obj = new OpenLayers.Layer.Image(this.name,
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this.url,
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this.extent,
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this.size,
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this.getOptions());
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}
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//get all additions from superclasses
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obj = OpenLayers.Layer.prototype.clone.apply(this, [obj]);
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// copy/set any non-init, non-simple values here
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return obj;
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},
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/**
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* APIMethod: setMap
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*
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* Parameters:
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* map - {<OpenLayers.Map>}
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*/
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setMap: function(map) {
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/**
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* If nothing to do with resolutions has been set, assume a single
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* resolution determined by ratio*extent/size - if an image has a
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* pixel aspect ratio different than one (as calculated above), the
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* image will be stretched in one dimension only.
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*/
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if( this.options.maxResolution == null ) {
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this.options.maxResolution = this.aspectRatio *
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this.extent.getWidth() /
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this.size.w;
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}
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OpenLayers.Layer.prototype.setMap.apply(this, arguments);
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},
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/**
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* Method: moveTo
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* Create the tile for the image or resize it for the new resolution
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*
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* Parameters:
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* bounds - {<OpenLayers.Bounds>}
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* zoomChanged - {Boolean}
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* dragging - {Boolean}
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*/
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moveTo:function(bounds, zoomChanged, dragging) {
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OpenLayers.Layer.prototype.moveTo.apply(this, arguments);
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var firstRendering = (this.tile == null);
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if(zoomChanged || firstRendering) {
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//determine new tile size
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this.setTileSize();
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//determine new position (upper left corner of new bounds)
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var ulPx = this.map.getLayerPxFromLonLat({
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lon: this.extent.left,
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lat: this.extent.top
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});
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if(firstRendering) {
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//create the new tile
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this.tile = new OpenLayers.Tile.Image(this, ulPx, this.extent,
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null, this.tileSize);
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this.addTileMonitoringHooks(this.tile);
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} else {
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//just resize the tile and set it's new position
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this.tile.size = this.tileSize.clone();
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this.tile.position = ulPx.clone();
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}
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this.tile.draw();
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}
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},
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/**
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* Set the tile size based on the map size.
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*/
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setTileSize: function() {
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var tileWidth = this.extent.getWidth() / this.map.getResolution();
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var tileHeight = this.extent.getHeight() / this.map.getResolution();
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this.tileSize = new OpenLayers.Size(tileWidth, tileHeight);
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},
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/**
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* Method: addTileMonitoringHooks
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* This function takes a tile as input and adds the appropriate hooks to
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* the tile so that the layer can keep track of the loading tiles.
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*
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* Parameters:
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* tile - {<OpenLayers.Tile>}
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*/
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addTileMonitoringHooks: function(tile) {
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tile.onLoadStart = function() {
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this.events.triggerEvent("loadstart");
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};
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tile.events.register("loadstart", this, tile.onLoadStart);
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tile.onLoadEnd = function() {
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this.events.triggerEvent("loadend");
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};
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tile.events.register("loadend", this, tile.onLoadEnd);
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tile.events.register("unload", this, tile.onLoadEnd);
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},
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/**
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* Method: removeTileMonitoringHooks
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* This function takes a tile as input and removes the tile hooks
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* that were added in <addTileMonitoringHooks>.
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*
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* Parameters:
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* tile - {<OpenLayers.Tile>}
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*/
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removeTileMonitoringHooks: function(tile) {
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tile.unload();
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tile.events.un({
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"loadstart": tile.onLoadStart,
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"loadend": tile.onLoadEnd,
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"unload": tile.onLoadEnd,
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scope: this
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});
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},
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/**
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* APIMethod: setUrl
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*
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* Parameters:
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* newUrl - {String}
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*/
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setUrl: function(newUrl) {
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this.url = newUrl;
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this.tile.draw();
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},
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/**
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* APIMethod: getURL
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* The url we return is always the same (the image itself never changes)
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* so we can ignore the bounds parameter (it will always be the same,
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* anyways)
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*
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* Parameters:
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* bounds - {<OpenLayers.Bounds>}
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*/
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getURL: function(bounds) {
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return this.url;
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},
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CLASS_NAME: "OpenLayers.Layer.Image"
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});
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