--- a/gnv-artifacts/src/main/java/de/intevation/gnv/raster/Vectorizer.java	Sat Dec 26 15:32:08 2009 +0000
+++ b/gnv-artifacts/src/main/java/de/intevation/gnv/raster/Vectorizer.java	Sun Dec 27 05:25:40 2009 +0000
@@ -38,6 +38,11 @@
             this.b = b;
         }
 
+        public Edge(Edge other) {
+            a = other.a;
+            b = other.b;
+        }
+
         public void chain(Edge other, int found) {
 
             if (found == a) {
@@ -70,7 +75,8 @@
         public int length() {
             int length = 0;
             Edge current = this;
-            do { ++length; } while ((current = current.next) != this);
+            do { ++length; } 
+            while ((current = current.next) != null && current != this);
             return length;
         }
 
@@ -92,6 +98,10 @@
 
         int length = edge.length();
 
+        if (length < 2) {
+            return e1;
+        }
+
         int count = 0;
 
         do {
@@ -118,7 +128,7 @@
                 ++count;
             }
         }
-        while (count < length + 2);
+        while (length > 1 && count < length + 2);
 
         return e1;
     }
@@ -171,7 +181,6 @@
     protected void emit(Edge edge) {
 
         Edge otherA = (Edge)openEdges.remove(edge.a);
-
         if (otherA != null) {
             otherA.chain(edge, edge.a);
         }