clean up input polygons

some inputs could consist of tiny line segments that are less than curveTolerance. Reduce the number of segments to the minimum necessary to satisfy tolerance constraints

svgnest.js

@@ -149,7 +149,8 @@
 			}
 
 			binPolygon = SvgParser.polygonify(bin);
-
+			binPolygon = this.cleanPolygon(binPolygon);
+
 			if(!binPolygon || binPolygon.length < 3){
 				return false;
 			}
@@ -511,8 +512,10 @@
 			var numChildren = paths.length;
 			for(i=0; i<numChildren; i++){
 				var poly = SvgParser.polygonify(paths[i]);
-
-				if(poly && poly.length > 2){
+				poly = this.cleanPolygon(poly);
+
+				// todo: warn user if poly could not be processed and is excluded from the nest
+				if(poly && poly.length > 2 && Math.abs(GeometryUtil.polygonArea(poly)) > config.curveTolerance*config.curveTolerance){
 					poly.source = i;					
 					polygons.push(poly);
 				}
@@ -572,7 +575,7 @@
 
 				return id;
 			};
-			
+
 			return polygons;
 		};
 
@@ -585,8 +588,6 @@
 
 			var p = this.svgToClipper(polygon);
 
-
-
 			var miterLimit = 2;
 			var co = new ClipperLib.ClipperOffset(miterLimit, config.curveTolerance*config.clipperScale);
 			co.AddPath(p, ClipperLib.JoinType.jtRound, ClipperLib.EndType.etClosedPolygon);
@@ -602,6 +603,37 @@
 			return result;
 		};
 
+		// returns a less complex polygon that satisfies the curve tolerance
+		this.cleanPolygon = function(polygon){
+			var p = this.svgToClipper(polygon);
+
+			// remove self-intersections and find the biggest polygon that's left
+			var simple = ClipperLib.Clipper.SimplifyPolygon(p, ClipperLib.PolyFillType.pftNonZero);
+
+			if(!simple || simple.length == 0){
+				return null;
+			}
+
+			var biggest = simple[0];
+			var biggestarea = Math.abs(GeometryUtil.polygonArea(biggest));
+			for(var i=1; i<simple.length; i++){
+				var area = Math.abs(GeometryUtil.polygonArea(simple[i]));
+				if(area > biggestarea){
+					biggest = simple[i];
+					biggestarea = area;
+				}
+			}
+
+			// clean up singularities, coincident points and edges
+			var clean = ClipperLib.Clipper.CleanPolygon(biggest, config.curveTolerance*config.clipperScale);
+
+			if(!clean || clean.length == 0){
+				return null;
+			}
+
+			return this.clipperToSvg(clean);
+		}
+
 		// converts a polygon from normal float coordinates to integer coordinates used by clipper, as well as x/y -> X/Y
 		this.svgToClipper = function(polygon){
 			var clip = [];