/* 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/Geometry/LineString.js
*/
/**
* Class: OpenLayers.Geometry.LinearRing
*
* A Linear Ring is a special LineString which is closed. It closes itself
* automatically on every addPoint/removePoint by adding a copy of the first
* point as the last point.
*
* Also, as it is the first in the line family to close itself, a getArea()
* function is defined to calculate the enclosed area of the linearRing
*
* Inherits:
* - <OpenLayers.Geometry.LineString>
*/
OpenLayers.Geometry.LinearRing = OpenLayers.Class(
OpenLayers.Geometry.LineString, {
/**
* Property: componentTypes
* {Array(String)} An array of class names representing the types of
* components that the collection can include. A null
* value means the component types are not restricted.
*/
componentTypes: ["OpenLayers.Geometry.Point"],
/**
* Constructor: OpenLayers.Geometry.LinearRing
* Linear rings are constructed with an array of points. This array
* can represent a closed or open ring. If the ring is open (the last
* point does not equal the first point), the constructor will close
* the ring. If the ring is already closed (the last point does equal
* the first point), it will be left closed.
*
* Parameters:
* points - {Array(<OpenLayers.Geometry.Point>)} points
*/
initialize: function(points) {
OpenLayers.Geometry.LineString.prototype.initialize.apply(this,
arguments);
},
/**
* APIMethod: addComponent
* Adds a point to geometry components. If the point is to be added to
* the end of the components array and it is the same as the last point
* already in that array, the duplicate point is not added. This has
* the effect of closing the ring if it is not already closed, and
* doing the right thing if it is already closed. This behavior can
* be overridden by calling the method with a non-null index as the
* second argument.
*
* Parameter:
* point - {<OpenLayers.Geometry.Point>}
* index - {Integer} Index into the array to insert the component
*
* Returns:
* {Boolean} Was the Point successfully added?
*/
addComponent: function(point, index) {
var added = false;
//remove last point
var lastPoint = this.components.pop();
// given an index, add the point
// without an index only add non-duplicate points
if(index != null || !point.equals(lastPoint)) {
added = OpenLayers.Geometry.Collection.prototype.addComponent.apply(this,
arguments);
}
//append copy of first point
var firstPoint = this.components[0];
OpenLayers.Geometry.Collection.prototype.addComponent.apply(this,
[firstPoint]);
return added;
},
/**
* APIMethod: removeComponent
* Removes a point from geometry components.
*
* Parameters:
* point - {<OpenLayers.Geometry.Point>}
*/
removeComponent: function(point) {
if (this.components.length > 4) {
//remove last point
this.components.pop();
//remove our point
OpenLayers.Geometry.Collection.prototype.removeComponent.apply(this,
arguments);
//append copy of first point
var firstPoint = this.components[0];
OpenLayers.Geometry.Collection.prototype.addComponent.apply(this,
[firstPoint]);
}
},
/**
* APIMethod: move
* Moves a geometry by the given displacement along positive x and y axes.
* This modifies the position of the geometry and clears the cached
* bounds.
*
* Parameters:
* x - {Float} Distance to move geometry in positive x direction.
* y - {Float} Distance to move geometry in positive y direction.
*/
move: function(x, y) {
for(var i = 0, len=this.components.length; i<len - 1; i++) {
this.components[i].move(x, y);
}
},
/**
* APIMethod: rotate
* Rotate a geometry around some origin
*
* Parameters:
* angle - {Float} Rotation angle in degrees (measured counterclockwise
* from the positive x-axis)
* origin - {<OpenLayers.Geometry.Point>} Center point for the rotation
*/
rotate: function(angle, origin) {
for(var i=0, len=this.components.length; i<len - 1; ++i) {
this.components[i].rotate(angle, origin);
}
},
/**
* APIMethod: resize
* Resize a geometry relative to some origin. Use this method to apply
* a uniform scaling to a geometry.
*
* Parameters:
* scale - {Float} Factor by which to scale the geometry. A scale of 2
* doubles the size of the geometry in each dimension
* (lines, for example, will be twice as long, and polygons
* will have four times the area).
* origin - {<OpenLayers.Geometry.Point>} Point of origin for resizing
* ratio - {Float} Optional x:y ratio for resizing. Default ratio is 1.
*
* Returns:
* {OpenLayers.Geometry} - The current geometry.
*/
resize: function(scale, origin, ratio) {
for(var i=0, len=this.components.length; i<len - 1; ++i) {
this.components[i].resize(scale, origin, ratio);
}
return this;
},
/**
* APIMethod: transform
* Reproject the components geometry from source to dest.
*
* Parameters:
* source - {<OpenLayers.Projection>}
* dest - {<OpenLayers.Projection>}
*
* Returns:
* {<OpenLayers.Geometry>}
*/
transform: function(source, dest) {
if (source && dest) {
for (var i=0, len=this.components.length; i<len - 1; i++) {
var component = this.components[i];
component.transform(source, dest);
}
this.bounds = null;
}
return this;
},
/**
* APIMethod: getCentroid
*
* Returns:
* {<OpenLayers.Geometry.Point>} The centroid of the collection
*/
getCentroid: function() {
if (this.components && (this.components.length > 2)) {
var sumX = 0.0;
var sumY = 0.0;
for (var i = 0; i < this.components.length - 1; i++) {
var b = this.components[i];
var c = this.components[i+1];
sumX += (b.x + c.x) * (b.x * c.y - c.x * b.y);
sumY += (b.y + c.y) * (b.x * c.y - c.x * b.y);
}
var area = -1 * this.getArea();
var x = sumX / (6 * area);
var y = sumY / (6 * area);
return new OpenLayers.Geometry.Point(x, y);
} else {
return null;
}
},
/**
* APIMethod: getArea
* Note - The area is positive if the ring is oriented CW, otherwise
* it will be negative.
*
* Returns:
* {Float} The signed area for a ring.
*/
getArea: function() {
var area = 0.0;
if ( this.components && (this.components.length > 2)) {
var sum = 0.0;
for (var i=0, len=this.components.length; i<len - 1; i++) {
var b = this.components[i];
var c = this.components[i+1];
sum += (b.x + c.x) * (c.y - b.y);
}
area = - sum / 2.0;
}
return area;
},
/**
* APIMethod: getGeodesicArea
* Calculate the approximate area of the polygon were it projected onto
* the earth. Note that this area will be positive if ring is oriented
* clockwise, otherwise it will be negative.
*
* Parameters:
* projection - {<OpenLayers.Projection>} The spatial reference system
* for the geometry coordinates. If not provided, Geographic/WGS84 is
* assumed.
*
* Reference:
* Robert. G. Chamberlain and William H. Duquette, "Some Algorithms for
* Polygons on a Sphere", JPL Publication 07-03, Jet Propulsion
* Laboratory, Pasadena, CA, June 2007 http://trs-new.jpl.nasa.gov/dspace/handle/2014/40409
*
* Returns:
* {float} The approximate signed geodesic area of the polygon in square
* meters.
*/
getGeodesicArea: function(projection) {
var ring = this; // so we can work with a clone if needed
if(projection) {
var gg = new OpenLayers.Projection("EPSG:4326");
if(!gg.equals(projection)) {
ring = this.clone().transform(projection, gg);
}
}
var area = 0.0;
var len = ring.components && ring.components.length;
if(len > 2) {
var p1, p2;
for(var i=0; i<len-1; i++) {
p1 = ring.components[i];
p2 = ring.components[i+1];
area += OpenLayers.Util.rad(p2.x - p1.x) *
(2 + Math.sin(OpenLayers.Util.rad(p1.y)) +
Math.sin(OpenLayers.Util.rad(p2.y)));
}
area = area * 6378137.0 * 6378137.0 / 2.0;
}
return area;
},
/**
* Method: containsPoint
* Test if a point is inside a linear ring. For the case where a point
* is coincident with a linear ring edge, returns 1. Otherwise,
* returns boolean.
*
* Parameters:
* point - {<OpenLayers.Geometry.Point>}
*
* Returns:
* {Boolean | Number} The point is inside the linear ring. Returns 1 if
* the point is coincident with an edge. Returns boolean otherwise.
*/
containsPoint: function(point) {
var approx = OpenLayers.Number.limitSigDigs;
var digs = 14;
var px = approx(point.x, digs);
var py = approx(point.y, digs);
function getX(y, x1, y1, x2, y2) {
return (((x1 - x2) * y) + ((x2 * y1) - (x1 * y2))) / (y1 - y2);
}
var numSeg = this.components.length - 1;
var start, end, x1, y1, x2, y2, cx, cy;
var crosses = 0;
for(var i=0; i<numSeg; ++i) {
start = this.components[i];
x1 = approx(start.x, digs);
y1 = approx(start.y, digs);
end = this.components[i + 1];
x2 = approx(end.x, digs);
y2 = approx(end.y, digs);
/**
* The following conditions enforce five edge-crossing rules:
* 1. points coincident with edges are considered contained;
* 2. an upward edge includes its starting endpoint, and
* excludes its final endpoint;
* 3. a downward edge excludes its starting endpoint, and
* includes its final endpoint;
* 4. horizontal edges are excluded; and
* 5. the edge-ray intersection point must be strictly right
* of the point P.
*/
if(y1 == y2) {
// horizontal edge
if(py == y1) {
// point on horizontal line
if(x1 <= x2 && (px >= x1 && px <= x2) || // right or vert
x1 >= x2 && (px <= x1 && px >= x2)) { // left or vert
// point on edge
crosses = -1;
break;
}
}
// ignore other horizontal edges
continue;
}
cx = approx(getX(py, x1, y1, x2, y2), digs);
if(cx == px) {
// point on line
if(y1 < y2 && (py >= y1 && py <= y2) || // upward
y1 > y2 && (py <= y1 && py >= y2)) { // downward
// point on edge
crosses = -1;
break;
}
}
if(cx <= px) {
// no crossing to the right
continue;
}
if(x1 != x2 && (cx < Math.min(x1, x2) || cx > Math.max(x1, x2))) {
// no crossing
continue;
}
if(y1 < y2 && (py >= y1 && py < y2) || // upward
y1 > y2 && (py < y1 && py >= y2)) { // downward
++crosses;
}
}
var contained = (crosses == -1) ?
// on edge
1 :
// even (out) or odd (in)
!!(crosses & 1);
return contained;
},
/**
* APIMethod: intersects
* Determine if the input geometry intersects this one.
*
* Parameters:
* geometry - {<OpenLayers.Geometry>} Any type of geometry.
*
* Returns:
* {Boolean} The input geometry intersects this one.
*/
intersects: function(geometry) {
var intersect = false;
if(geometry.CLASS_NAME == "OpenLayers.Geometry.Point") {
intersect = this.containsPoint(geometry);
} else if(geometry.CLASS_NAME == "OpenLayers.Geometry.LineString") {
intersect = geometry.intersects(this);
} else if(geometry.CLASS_NAME == "OpenLayers.Geometry.LinearRing") {
intersect = OpenLayers.Geometry.LineString.prototype.intersects.apply(
this, [geometry]
);
} else {
// check for component intersections
for(var i=0, len=geometry.components.length; i<len; ++ i) {
intersect = geometry.components[i].intersects(this);
if(intersect) {
break;
}
}
}
return intersect;
},
/**
* 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) {
return (nodes === true) ? [] : this.components.slice(0, this.components.length-1);
},
CLASS_NAME: "OpenLayers.Geometry.LinearRing"
});