[Mapbender-commits] r3135 - trunk/mapbender/http/javascripts

[svn_mapbender at osgeo.org]

Author: nimix
Date: 2008-10-07 03:47:52 -0400 (Tue, 07 Oct 2008)
New Revision: 3135

Modified:
   trunk/mapbender/http/javascripts/geometry.js
Log:
add line buffering function

Modified: trunk/mapbender/http/javascripts/geometry.js
===================================================================
--- trunk/mapbender/http/javascripts/geometry.js	2008-10-07 07:47:26 UTC (rev 3134)
+++ trunk/mapbender/http/javascripts/geometry.js	2008-10-07 07:47:52 UTC (rev 3135)
@@ -1049,6 +1049,111 @@
 	return true;
 };
 
+/**
+ * creates a polygon geometry object which form a buffer around the line geometry
+ * 
+ * @param {float} real world units to buffer around the line
+ * @param {float} (optional) units to buffer around the line in Y direction
+ * 
+ * @return linebuffer polygon
+ * @type Geometry
+ */
+Geometry.prototype.bufferLine = function(bufferX, bufferY){
+	if(typeof(bufferY)=='undefined')
+		bufferY = bufferX;
+	if(this.geomType!=geomType.line || this.count()<2)
+		return false;
+	
+	var ret = new Geometry(geomType.polygon)
+	
+	//get vector from point 0 to point 1
+	last_vec = this.get(1).minus(this.get(0));
+
+	//get 90° rotated vector
+	last_vec_o = new Point(-last_vec.y, last_vec.x);
+
+	//resize vectors with apropriate linebuffer length
+	last_vec_o = last_vec_o.dividedBy(last_vec_o.dist(new Point(0,0)));
+	last_vec_o.x*=bufferX; last_vec_o.y*=bufferY;
+	last_vec = last_vec.dividedBy(last_vec.dist(new Point(0,0)));
+	last_vec.x*=bufferX; last_vec.y*=bufferY;
+		
+	//add first pointsets
+	ret.list.unshift(this.get(0).plus(last_vec_o).minus(last_vec));
+	ret.list.push(this.get(0).minus(last_vec_o).minus(last_vec));
+		
+	for(var i=1;i<this.count()-1;i++){
+		//get vector from point n to point n+1
+		vec = this.get(i+1).minus(this.get(i));
+		//get orthogonal (90° rotated) vector		
+		vec_o = new Point(-vec.y, vec.x);
+
+		//resize vectors to linebuffer length
+		vec_o = vec_o.dividedBy(vec_o.dist(new Point(0,0)));
+		vec_o.x*=bufferX; vec_o.y*=bufferY;
+		vec = vec.dividedBy(vec.dist(new Point(0,0)));
+		vec.x*=bufferX; vec.y*=bufferY;
+			
+		//if direction is the same continue
+		if(vec.equals(last_vec))
+			continue;
+			
+		// calculate directed angle between the two vectors by 
+		// calculating the argument diffenrences between complex numbers
+		// arg(x + i*y) (because law of cosine can onlycalculate undirected angle)
+		var angle = (Math.atan2(vec.x,vec.y)-Math.atan2(last_vec.x,last_vec.y))
+		//ensure that angle is -180<=angle<=180
+		if(angle<-Math.PI)angle=2*Math.PI+angle;
+		if(angle>+Math.PI)angle=2*Math.PI-angle;
+		console.log(angle);
+		
+		//calculate the distance between the next points on boundary
+		//and the line point
+		//the point will be in the direction of angle/2 relative to last_vec_o
+		//since cosine is adjacent side / hypothenuse and we know that 
+		//the adjacent side is lineBuffer the hypothenus (our distance) is
+		var ndist = 1/(Math.cos(angle/2))
+		//direction of next points on boundary
+		var int_vec = vec_o.plus(last_vec_o);
+		//resize direction vector to our distance
+		int_vec = int_vec.times(ndist/int_vec.dist(new Point(0,0)));
+		int_vec.x*=bufferX; int_vec.y*=bufferY;
+		
+		//look if we have an outer sharp corner (>90°)
+		if(angle>Math.PI/2){
+			//push cutted edge points
+			ret.list.unshift(this.get(i).plus(last_vec_o).plus(last_vec));
+			ret.list.unshift(this.get(i).plus(vec_o).minus(vec));
+		}
+		else{
+			//push inner/light edge
+			ret.list.unshift(this.get(i).plus(int_vec));
+		}
+
+		//look if we have an inner sharp corner (<-90°)
+		if(angle<-Math.PI/2){
+			//push cutted edge points
+			ret.list.push(this.get(i).minus(last_vec_o).plus(last_vec));
+			ret.list.push(this.get(i).minus(vec_o).minus(vec));
+		}
+		else{
+			//push inner/light edge
+			ret.list.push(this.get(i).minus(int_vec));
+		}
+			
+		//copy for next point
+		last_vec = vec;
+		last_vec_o = vec_o;
+	}
+	//add last pointsets
+	ret.list.unshift(this.get(i).plus(last_vec_o).plus(last_vec));
+	ret.list.push(this.get(i).minus(last_vec_o).plus(last_vec));
+	
+	ret.close();
+
+	return ret;	
+}
+
 Geometry.prototype.toString = function () {
 	var str = "";
 	
@@ -1087,8 +1192,6 @@
 	return str;
 };
 
-
-
 /**
  * @class an array of elements, each consisting of a name/value pair
  *