Changed the SINK_CUT and FREE_NODE constants so that when we use graph

cuts on an image the result is a displayable binary image rather than
an image which is super dark and hard to view.

dlib/graph_cuts/min_cut.h

@@ -24,8 +24,8 @@ namespace dlib
 // ----------------------------------------------------------------------------------------
 
     const node_label SOURCE_CUT = 0;
-    const node_label SINK_CUT = 1;
-    const node_label FREE_NODE = 2;
+    const node_label SINK_CUT = 254;
+    const node_label FREE_NODE = 255;
 
 // ----------------------------------------------------------------------------------------
 

dlib/graph_cuts/min_cut_abstract.h

@@ -17,8 +17,8 @@ namespace dlib
 
     typedef unsigned char node_label;
     const node_label SOURCE_CUT = 0;
-    const node_label SINK_CUT = 1;
-    const node_label FREE_NODE = 2;
+    const node_label SINK_CUT = 254;
+    const node_label FREE_NODE = 255;
 
 // ----------------------------------------------------------------------------------------