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