/* Copyright (c) 2006-2010 by OpenLayers Contributors (see authors.txt for
* full list of contributors). Published under the Clear BSD license.
* See http://svn.openlayers.org/trunk/openlayers/license.txt for the
* full text of the license. */
/**
* @requires OpenLayers/Util.js
*/
/**
* Class: OpenLayers.Projection
* Class for coordinate transforms between coordinate systems.
* Depends on the proj4js library. If proj4js is not available,
* then this is just an empty stub.
*/
OpenLayers.Projection = OpenLayers.Class({
/**
* Property: proj
* {Object} Proj4js.Proj instance.
*/
proj: null,
/**
* Property: projCode
* {String}
*/
projCode: null,
/**
* Constructor: OpenLayers.Projection
* This class offers several methods for interacting with a wrapped
* pro4js projection object.
*
* Parameters:
* projCode - {String} A string identifying the Well Known Identifier for
* the projection.
* options - {Object} An optional object to set additional properties
* on the layer.
*
* Returns:
* {<OpenLayers.Projection>} A projection object.
*/
initialize: function(projCode, options) {
OpenLayers.Util.extend(this, options);
this.projCode = projCode;
if (window.Proj4js) {
this.proj = new Proj4js.Proj(projCode);
}
},
/**
* APIMethod: getCode
* Get the string SRS code.
*
* Returns:
* {String} The SRS code.
*/
getCode: function() {
return this.proj ? this.proj.srsCode : this.projCode;
},
/**
* APIMethod: getUnits
* Get the units string for the projection -- returns null if
* proj4js is not available.
*
* Returns:
* {String} The units abbreviation.
*/
getUnits: function() {
return this.proj ? this.proj.units : null;
},
/**
* Method: toString
* Convert projection to string (getCode wrapper).
*
* Returns:
* {String} The projection code.
*/
toString: function() {
return this.getCode();
},
/**
* Method: equals
* Test equality of two projection instances. Determines equality based
* soley on the projection code.
*
* Returns:
* {Boolean} The two projections are equivalent.
*/
equals: function(projection) {
if (projection && projection.getCode) {
return this.getCode() == projection.getCode();
} else {
return false;
}
},
/* Method: destroy
* Destroy projection object.
*/
destroy: function() {
delete this.proj;
delete this.projCode;
},
CLASS_NAME: "OpenLayers.Projection"
});
/**
* Property: transforms
* Transforms is an object, with from properties, each of which may
* have a to property. This allows you to define projections without
* requiring support for proj4js to be included.
*
* This object has keys which correspond to a 'source' projection object. The
* keys should be strings, corresponding to the projection.getCode() value.
* Each source projection object should have a set of destination projection
* keys included in the object.
*
* Each value in the destination object should be a transformation function,
* where the function is expected to be passed an object with a .x and a .y
* property. The function should return the object, with the .x and .y
* transformed according to the transformation function.
*
* Note - Properties on this object should not be set directly. To add a
* transform method to this object, use the <addTransform> method. For an
* example of usage, see the OpenLayers.Layer.SphericalMercator file.
*/
OpenLayers.Projection.transforms = {};
/**
* APIMethod: addTransform
* Set a custom transform method between two projections. Use this method in
* cases where the proj4js lib is not available or where custom projections
* need to be handled.
*
* Parameters:
* from - {String} The code for the source projection
* to - {String} the code for the destination projection
* method - {Function} A function that takes a point as an argument and
* transforms that point from the source to the destination projection
* in place. The original point should be modified.
*/
OpenLayers.Projection.addTransform = function(from, to, method) {
if(!OpenLayers.Projection.transforms[from]) {
OpenLayers.Projection.transforms[from] = {};
}
OpenLayers.Projection.transforms[from][to] = method;
};
/**
* APIMethod: transform
* Transform a point coordinate from one projection to another. Note that
* the input point is transformed in place.
*
* Parameters:
* point - {{OpenLayers.Geometry.Point> | Object} An object with x and y
* properties representing coordinates in those dimensions.
* sourceProj - {OpenLayers.Projection} Source map coordinate system
* destProj - {OpenLayers.Projection} Destination map coordinate system
*
* Returns:
* point - {object} A transformed coordinate. The original point is modified.
*/
OpenLayers.Projection.transform = function(point, source, dest) {
if (source.proj && dest.proj) {
point = Proj4js.transform(source.proj, dest.proj, point);
} else if (source && dest &&
OpenLayers.Projection.transforms[source.getCode()] &&
OpenLayers.Projection.transforms[source.getCode()][dest.getCode()]) {
OpenLayers.Projection.transforms[source.getCode()][dest.getCode()](point);
}
return point;
};
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