hackedteam/rcs-console

package it.ht.rcs.console.operations.view.configuration.advanced.renderers.utils {
    
    import flash.geom.Point;
    
    
    /**
     * 
     * Copyright (c) 2008 Noel Billig (www.dncompute.com)
     * 
     * Permission is hereby granted, free of charge, to any person obtaining a copy
     * of this software and associated documentation files (the "Software"), to deal
     * in the Software without restriction, including without limitation the rights
     * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     * copies of the Software, and to permit persons to whom the Software is
     * furnished to do so, subject to the following conditions:
     *
     * The above copyright notice and this permission notice shall be included in
     * all copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
     * THE SOFTWARE.
     * 
     */
     
    /**
     * 
     * The line segment intersection code used here is based off of Erik Gustavsson's 
     * tutorial found here: http://www.zikko.se/resources/lineIntersection.php
     * That page reads: "All content on these pages may be used, copied and modifed freely."
     * 
     */
    public class GeomUtil {
        
        /**
         *
         * Returns the point of intersection between the line connecting point a1 to a2
         * and the line connecting point b1 to b2.
         *
         */
        public static function getLineSegmentIntersection(
                a1:Point,a2:Point,
                b1:Point,b2:Point
                ):Point {
            
            //XXX: Add an optimization here to see if the bounding boxes even overlap
            
            //Figure out where the lines intersect
            var intersection:Point = getLineIntersection(a1,a2,b1,b2);
            
            //They could be parellel, in which case there is no line intersection
            if (intersection == null) return null;
            
            //If the lines intersect, check and see if the intersection falls on the segments
            if (inRange(intersection,a1,a2) && inRange(intersection,b1,b2)) {
                return intersection;
            }
            
            return null;
            
        }
        
        
        /**
         *
         * Calculate the intersection between two lines. The intersection point
         * may not necesarily occur on either line segment. To only get the line
         * segment intersection, use <code>getLineSegmentIntersection</code> instead
         *
         */
        public static function getLineIntersection ( 
                a1:Point,a2:Point,
                b1:Point,b2:Point
                ):Point {
        
            //calculate directional constants
            var k1:Number = (a2.y-a1.y) / (a2.x-a1.x);
            var k2:Number = (b2.y-b1.y) / (b2.x-b1.x);
            
            // if the directional constants are equal, the lines are parallel,
            // meaning there is no intersection point.
            if( k1 == k2 ) return null;
            
            var x:Number,y:Number;
            var m1:Number,m2:Number;
            
            // an infinite directional constant means the line is vertical
            if( !isFinite(k1) ) {
                
                // so the intersection must be at the x coordinate of the line
                x = a1.x;
                m2 = b1.y - k2 * b1.x;
                y = k2 * x + m2;
                
            // same as above for line 2
            } else if ( !isFinite(k2) ) {
                
                m1 = a1.y - k1 * a1.x;
                x = b1.x;
                y = k1 * x + m1;

            // if neither of the lines are vertical
            } else {
                
                m1 = a1.y - k1 * a1.x;
                m2 = b1.y - k2 * b1.x;                
                x = (m1-m2) / (k2-k1);
                y = k1 * x + m1;
                
            }
            
            return new Point(x,y);
        }
        
        
        private static function inRange(pnt:Point,a:Point,b:Point):Boolean {
            
            if (a.x != b.x) {
                return pnt.x <= a.x != pnt.x < b.x;
            } else {
                return pnt.y <= a.y != pnt.y < b.y;
            }
            
        }
        
        
    }
    
}