/* 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/Format/WKT.js
* @requires OpenLayers/Feature/Vector.js
*/
/**
* Class: OpenLayers.Geometry
* A Geometry is a description of a geographic object. Create an instance of
* this class with the <OpenLayers.Geometry> constructor. This is a base class,
* typical geometry types are described by subclasses of this class.
*/
OpenLayers.Geometry = OpenLayers.Class({
/**
* Property: id
* {String} A unique identifier for this geometry.
*/
id: null,
/**
* Property: parent
* {<OpenLayers.Geometry>}This is set when a Geometry is added as component
* of another geometry
*/
parent: null,
/**
* Property: bounds
* {<OpenLayers.Bounds>} The bounds of this geometry
*/
bounds: null,
/**
* Constructor: OpenLayers.Geometry
* Creates a geometry object.
*/
initialize: function() {
this.id = OpenLayers.Util.createUniqueID(this.CLASS_NAME+ "_");
},
/**
* Method: destroy
* Destroy this geometry.
*/
destroy: function() {
this.id = null;
this.bounds = null;
},
/**
* APIMethod: clone
* Create a clone of this geometry. Does not set any non-standard
* properties of the cloned geometry.
*
* Returns:
* {<OpenLayers.Geometry>} An exact clone of this geometry.
*/
clone: function() {
return new OpenLayers.Geometry();
},
/**
* Set the bounds for this Geometry.
*
* Parameters:
* object - {<OpenLayers.Bounds>}
*/
setBounds: function(bounds) {
if (bounds) {
this.bounds = bounds.clone();
}
},
/**
* Method: clearBounds
* Nullify this components bounds and that of its parent as well.
*/
clearBounds: function() {
this.bounds = null;
if (this.parent) {
this.parent.clearBounds();
}
},
/**
* Method: extendBounds
* Extend the existing bounds to include the new bounds.
* If geometry's bounds is not yet set, then set a new Bounds.
*
* Parameters:
* newBounds - {<OpenLayers.Bounds>}
*/
extendBounds: function(newBounds){
var bounds = this.getBounds();
if (!bounds) {
this.setBounds(newBounds);
} else {
this.bounds.extend(newBounds);
}
},
/**
* APIMethod: getBounds
* Get the bounds for this Geometry. If bounds is not set, it
* is calculated again, this makes queries faster.
*
* Returns:
* {<OpenLayers.Bounds>}
*/
getBounds: function() {
if (this.bounds == null) {
this.calculateBounds();
}
return this.bounds;
},
/**
* APIMethod: calculateBounds
* Recalculate the bounds for the geometry.
*/
calculateBounds: function() {
//
// This should be overridden by subclasses.
//
},
/**
* APIMethod: distanceTo
* Calculate the closest distance between two geometries (on the x-y plane).
*
* Parameters:
* geometry - {<OpenLayers.Geometry>} The target geometry.
* options - {Object} Optional properties for configuring the distance
* calculation.
*
* Valid options depend on the specific geometry type.
*
* Returns:
* {Number | Object} The distance between this geometry and the target.
* If details is true, the return will be an object with distance,
* x0, y0, x1, and x2 properties. The x0 and y0 properties represent
* the coordinates of the closest point on this geometry. The x1 and y1
* properties represent the coordinates of the closest point on the
* target geometry.
*/
distanceTo: function(geometry, options) {
},
/**
* APIMethod: getVertices
* Return a list of all points in this geometry.
*
* Parameters:
* nodes - {Boolean} For lines, only return vertices that are
* endpoints. If false, for lines, only vertices that are not
* endpoints will be returned. If not provided, all vertices will
* be returned.
*
* Returns:
* {Array} A list of all vertices in the geometry.
*/
getVertices: function(nodes) {
},
/**
* Method: atPoint
* Note - This is only an approximation based on the bounds of the
* geometry.
*
* Parameters:
* lonlat - {<OpenLayers.LonLat>}
* toleranceLon - {float} Optional tolerance in Geometric Coords
* toleranceLat - {float} Optional tolerance in Geographic Coords
*
* Returns:
* {Boolean} Whether or not the geometry is at the specified location
*/
atPoint: function(lonlat, toleranceLon, toleranceLat) {
var atPoint = false;
var bounds = this.getBounds();
if ((bounds != null) && (lonlat != null)) {
var dX = (toleranceLon != null) ? toleranceLon : 0;
var dY = (toleranceLat != null) ? toleranceLat : 0;
var toleranceBounds =
new OpenLayers.Bounds(this.bounds.left - dX,
this.bounds.bottom - dY,
this.bounds.right + dX,
this.bounds.top + dY);
atPoint = toleranceBounds.containsLonLat(lonlat);
}
return atPoint;
},
/**
* Method: getLength
* Calculate the length of this geometry. This method is defined in
* subclasses.
*
* Returns:
* {Float} The length of the collection by summing its parts
*/
getLength: function() {
//to be overridden by geometries that actually have a length
//
return 0.0;
},
/**
* Method: getArea
* Calculate the area of this geometry. This method is defined in subclasses.
*
* Returns:
* {Float} The area of the collection by summing its parts
*/
getArea: function() {
//to be overridden by geometries that actually have an area
//
return 0.0;
},
/**
* APIMethod: getCentroid
* Calculate the centroid of this geometry. This method is defined in subclasses.
*
* Returns:
* {<OpenLayers.Geometry.Point>} The centroid of the collection
*/
getCentroid: function() {
return null;
},
/**
* Method: toString
* Returns the Well-Known Text representation of a geometry
*
* Returns:
* {String} Well-Known Text
*/
toString: function() {
return OpenLayers.Format.WKT.prototype.write(
new OpenLayers.Feature.Vector(this)
);
},
CLASS_NAME: "OpenLayers.Geometry"
});
/**
* Function: OpenLayers.Geometry.fromWKT
* Generate a geometry given a Well-Known Text string.
*
* Parameters:
* wkt - {String} A string representing the geometry in Well-Known Text.
*
* Returns:
* {<OpenLayers.Geometry>} A geometry of the appropriate class.
*/
OpenLayers.Geometry.fromWKT = function(wkt) {
var format = arguments.callee.format;
if(!format) {
format = new OpenLayers.Format.WKT();
arguments.callee.format = format;
}
var geom;
var result = format.read(wkt);
if(result instanceof OpenLayers.Feature.Vector) {
geom = result.geometry;
} else if(result instanceof Array) {
var len = result.length;
var components = new Array(len);
for(var i=0; i<len; ++i) {
components[i] = result[i].geometry;
}
geom = new OpenLayers.Geometry.Collection(components);
}
return geom;
};
/**
* Method: OpenLayers.Geometry.segmentsIntersect
* Determine whether two line segments intersect. Optionally calculates
* and returns the intersection point. This function is optimized for
* cases where seg1.x2 >= seg2.x1 || seg2.x2 >= seg1.x1. In those
* obvious cases where there is no intersection, the function should
* not be called.
*
* Parameters:
* seg1 - {Object} Object representing a segment with properties x1, y1, x2,
* and y2. The start point is represented by x1 and y1. The end point
* is represented by x2 and y2. Start and end are ordered so that x1 < x2.
* seg2 - {Object} Object representing a segment with properties x1, y1, x2,
* and y2. The start point is represented by x1 and y1. The end point
* is represented by x2 and y2. Start and end are ordered so that x1 < x2.
* options - {Object} Optional properties for calculating the intersection.
*
* Valid options:
* point - {Boolean} Return the intersection point. If false, the actual
* intersection point will not be calculated. If true and the segments
* intersect, the intersection point will be returned. If true and
* the segments do not intersect, false will be returned. If true and
* the segments are coincident, true will be returned.
* tolerance - {Number} If a non-null value is provided, if the segments are
* within the tolerance distance, this will be considered an intersection.
* In addition, if the point option is true and the calculated intersection
* is within the tolerance distance of an end point, the endpoint will be
* returned instead of the calculated intersection. Further, if the
* intersection is within the tolerance of endpoints on both segments, or
* if two segment endpoints are within the tolerance distance of eachother
* (but no intersection is otherwise calculated), an endpoint on the
* first segment provided will be returned.
*
* Returns:
* {Boolean | <OpenLayers.Geometry.Point>} The two segments intersect.
* If the point argument is true, the return will be the intersection
* point or false if none exists. If point is true and the segments
* are coincident, return will be true (and the instersection is equal
* to the shorter segment).
*/
OpenLayers.Geometry.segmentsIntersect = function(seg1, seg2, options) {
var point = options && options.point;
var tolerance = options && options.tolerance;
var intersection = false;
var x11_21 = seg1.x1 - seg2.x1;
var y11_21 = seg1.y1 - seg2.y1;
var x12_11 = seg1.x2 - seg1.x1;
var y12_11 = seg1.y2 - seg1.y1;
var y22_21 = seg2.y2 - seg2.y1;
var x22_21 = seg2.x2 - seg2.x1;
var d = (y22_21 * x12_11) - (x22_21 * y12_11);
var n1 = (x22_21 * y11_21) - (y22_21 * x11_21);
var n2 = (x12_11 * y11_21) - (y12_11 * x11_21);
if(d == 0) {
// parallel
if(n1 == 0 && n2 == 0) {
// coincident
intersection = true;
}
} else {
var along1 = n1 / d;
var along2 = n2 / d;
if(along1 >= 0 && along1 <= 1 && along2 >=0 && along2 <= 1) {
// intersect
if(!point) {
intersection = true;
} else {
// calculate the intersection point
var x = seg1.x1 + (along1 * x12_11);
var y = seg1.y1 + (along1 * y12_11);
intersection = new OpenLayers.Geometry.Point(x, y);
}
}
}
if(tolerance) {
var dist;
if(intersection) {
if(point) {
var segs = [seg1, seg2];
var seg, x, y;
// check segment endpoints for proximity to intersection
// set intersection to first endpoint within the tolerance
outer: for(var i=0; i<2; ++i) {
seg = segs[i];
for(var j=1; j<3; ++j) {
x = seg["x" + j];
y = seg["y" + j];
dist = Math.sqrt(
Math.pow(x - intersection.x, 2) +
Math.pow(y - intersection.y, 2)
);
if(dist < tolerance) {
intersection.x = x;
intersection.y = y;
break outer;
}
}
}
}
} else {
// no calculated intersection, but segments could be within
// the tolerance of one another
var segs = [seg1, seg2];
var source, target, x, y, p, result;
// check segment endpoints for proximity to intersection
// set intersection to first endpoint within the tolerance
outer: for(var i=0; i<2; ++i) {
source = segs[i];
target = segs[(i+1)%2];
for(var j=1; j<3; ++j) {
p = {x: source["x"+j], y: source["y"+j]};
result = OpenLayers.Geometry.distanceToSegment(p, target);
if(result.distance < tolerance) {
if(point) {
intersection = new OpenLayers.Geometry.Point(p.x, p.y);
} else {
intersection = true;
}
break outer;
}
}
}
}
}
return intersection;
};
/**
* Function: OpenLayers.Geometry.distanceToSegment
*
* Parameters:
* point - {Object} An object with x and y properties representing the
* point coordinates.
* segment - {Object} An object with x1, y1, x2, and y2 properties
* representing endpoint coordinates.
*
* Returns:
* {Object} An object with distance, x, and y properties. The distance
* will be the shortest distance between the input point and segment.
* The x and y properties represent the coordinates along the segment
* where the shortest distance meets the segment.
*/
OpenLayers.Geometry.distanceToSegment = function(point, segment) {
var x0 = point.x;
var y0 = point.y;
var x1 = segment.x1;
var y1 = segment.y1;
var x2 = segment.x2;
var y2 = segment.y2;
var dx = x2 - x1;
var dy = y2 - y1;
var along = ((dx * (x0 - x1)) + (dy * (y0 - y1))) /
(Math.pow(dx, 2) + Math.pow(dy, 2));
var x, y;
if(along <= 0.0) {
x = x1;
y = y1;
} else if(along >= 1.0) {
x = x2;
y = y2;
} else {
x = x1 + along * dx;
y = y1 + along * dy;
}
return {
distance: Math.sqrt(Math.pow(x - x0, 2) + Math.pow(y - y0, 2)),
x: x, y: y
};
};