add geometry.intersects method for all geometry types (closes #1072)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@5458 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
2007-12-17 06:05:35 +00:00
parent 189b12d020
commit 5667311cba
9 changed files with 1135 additions and 1 deletions
@@ -174,6 +174,125 @@ OpenLayers.Geometry.LinearRing = OpenLayers.Class(
        }
        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 px = point.x;
+        var py = point.y;
+        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 = start.x;
+            y1 = start.y;
+            end = this.components[i + 1];
+            x2 = end.x;
+            y2 = end.y;
+            
+            /**
+             * 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 = getX(py, x1, y1, x2, y2);
+            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(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; i<geometry.components.length; ++ i) {
+                intersect = geometry.components[i].intersects(this);
+                if(intersect) {
+                    break;
+                }
+            }
+        }
+        return intersect;
+    },

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