adds flood fill algorithm

shared/src/FloodFill.h

@@ -0,0 +1,96 @@
+//
+//  FloodFill.h
+//  hifi
+//
+//  Created by Tobias Schwinger 3/26/13.
+//  Copyright (c) 2013 High Fidelity, Inc. All rights reserved.
+//
+
+#ifndef __hifi__FloodFill__
+#define __hifi__FloodFill__
+
+/**
+ * Line scanning, iterative flood fill algorithm.
+ */
+template< class Strategy, typename Cursor >
+void floodFill(Cursor const& position,
+        Strategy const& strategy = Strategy());
+
+
+template< class Strategy, typename Cursor > 
+struct floodFill_impl : Strategy
+{
+    floodFill_impl(Strategy const& s) : Strategy(s) { }
+
+    using Strategy::select;
+    using Strategy::process;
+
+    using Strategy::left;
+    using Strategy::right;
+    using Strategy::up;
+    using Strategy::down;
+
+    using Strategy::defer;
+    using Strategy::deferred;
+
+    void go(Cursor position)
+    {
+        Cursor higher, lower, h,l, i;
+        bool higher_found, lower_found, hf, lf;
+        do
+        {
+            if (! select(position))
+                continue;
+
+            process(position);
+
+            Cursor higher = position, lower = position;
+            bool higher_found = false;
+            bool lower_found = false;
+            up(higher); yTest(higher, higher_found);
+            down(lower); yTest(lower, lower_found);
+
+            i = position, h = higher, l = lower;
+            hf = higher_found, lf = lower_found;
+            do { right(i), right(h), right(l); yTest(h,hf); yTest(l,lf); }
+            while (selectAndProcess(i));
+
+            i = position, h = higher, l = lower;
+            hf = higher_found, lf = lower_found;
+            do { left(i); left(h); left(l); yTest(h,hf); yTest(l,lf); }
+            while (selectAndProcess(i));
+        }
+        while (deferred(position));
+    }
+
+    bool selectAndProcess(Cursor const& i)
+    {
+        if (select(i))
+        {
+            process(i);
+            return true;
+        }
+        return false;
+    }
+
+    void yTest(Cursor const& i, bool& state)
+    {
+        if (! select(i))
+            state = false;
+        else if (! state)
+        {
+            state = true;
+            defer(i);
+        }
+    }
+};
+
+template< class Strategy, typename Cursor >
+void floodFill(Cursor const& p, Strategy const& s)
+{
+    floodFill_impl<Strategy,Cursor>(s).go(p);
+}
+
+
+#endif
+