polygon.js

用来在地图上做操作GIS,在地图上做标记

/* Copyright (c) 2006-2007 MetaCarta, Inc., published under the BSD license.
 * See http://svn.openlayers.org/trunk/openlayers/release-license.txt 
 * for the full text of the license. */

/**
 * @requires OpenLayers/Geometry/Collection.js
 * 
 * Class: OpenLayers.Geometry.Polygon 
 * Polygon is a collection of Geometry.LinearRings. 
 * 
 * Inherits from:
 *  - <OpenLayers.Geometry.Collection> 
 *  - <OpenLayers.Geometry> 
 */
OpenLayers.Geometry.Polygon = OpenLayers.Class(
  OpenLayers.Geometry.Collection, {

    /**
     * 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.LinearRing"],

    /**
     * Constructor: OpenLayers.Geometry.Polygon
     * Constructor for a Polygon geometry. 
     * The first ring (this.component[0])is the outer bounds of the polygon and 
     * all subsequent rings (this.component[1-n]) are internal holes.
     *
     *
     * Parameters:
     * components - Array({<OpenLayers.Geometry.LinearRing>}) 
     */
    initialize: function(components) {
        OpenLayers.Geometry.Collection.prototype.initialize.apply(this, 
                                                                  arguments);
    },
    
    /** 
     * APIMethod: getArea
     * Calculated by subtracting the areas of the internal holes from the 
     *   area of the outer hole.
     * 
     * Returns:
     * {float} The area of the geometry
     */
    getArea: function() {
        var area = 0.0;
        if ( this.components && (this.components.length > 0)) {
            area += Math.abs(this.components[0].getArea());
            for (var i = 1; i < this.components.length; i++) {
                area -= Math.abs(this.components[i].getArea());
            }
        }
        return area;
    },

    CLASS_NAME: "OpenLayers.Geometry.Polygon"
});

/**
 * APIMethod: createRegularPolygon
 * Create a regular polygon around a radius. Useful for creating circles 
 * and the like.
 *
 * Parameters:
 * origin - {<OpenLayers.Geometry.Point>} center of polygon.
 * radius - {Float} distance to vertex, in map units.
 * sides - {Integer} Number of sides. 20 approximates a circle.
 * rotation - {Float} original angle of rotation, in degrees.
 */
OpenLayers.Geometry.Polygon.createRegularPolygon = function(origin, radius, sides, rotation) {  
    var angle = Math.PI * ((1/sides) - (1/2));
    if(rotation) {
        angle += (rotation / 180) * Math.PI;
    }
    var rotateAngle, x, y;
    var points = [];
    for(var i=0; i<sides; ++i) {
        rotatedAngle = angle + (i * 2 * Math.PI / sides);
        x = origin.x + (radius * Math.cos(rotatedAngle));
        y = origin.y + (radius * Math.sin(rotatedAngle));
        points.push(new OpenLayers.Geometry.Point(x, y));
    }
    var ring = new OpenLayers.Geometry.LinearRing(points);
    return new OpenLayers.Geometry.Polygon([ring]);
}