--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gnv-artifacts/src/main/java/de/intevation/gnv/raster/Vectorizer.java	Mon Dec 21 18:00:54 2009 +0000
@@ -0,0 +1,289 @@
+package de.intevation.gnv.raster;
+
+import java.util.BitSet;
+import java.util.List;
+import java.util.ArrayList;
+
+import gnu.trove.TIntStack;
+import gnu.trove.TIntObjectHashMap;
+
+/**
+ * @author Sascha L. Teichmann (sascha.teichmann@intevation.de)
+ */
+public class Vectorizer
+{
+    public interface RingsHandler {
+
+        void handleRings(List rings, int value, int width);
+
+    } // interface RingsHandler
+
+    public static final class Edge {
+
+        public Edge prev;
+        public Edge next;
+
+        public int a;
+        public int b;
+
+        public Edge() {
+        }
+
+        public Edge(int a, int b) {
+            this.a = a;
+            this.b = b;
+        }
+
+        public void chain(Edge other, int found) {
+
+            if (found == a) {
+                other.next = this;
+                prev = other;
+                return;
+            }
+
+            if (found == b) {
+                next = other;
+                other.prev = this;
+                return;
+            }
+
+            throw new IllegalStateException("cannot chain");
+        }
+
+        public boolean isComplete() {
+            Edge current = this;
+            do {
+                if (current.prev == null || current.next == null) {
+                    return false;
+                }
+                current = current.next;
+            }
+            while (current != this);
+            return true;
+        }
+
+        public int length() {
+            int length = 0;
+            Edge current = this;
+            do { ++length; } while ((current = current.next) != this);
+            return length;
+        }
+    } // class Edge
+
+    protected static Edge simplify(Edge edge, int width) {
+
+        Edge e1 = edge;
+        Edge e2 = edge.next;
+        Edge e3 = e2.next;
+
+        int length = edge.length();
+
+        int count = 0;
+
+        do {
+            int e1x = e1.a % width;
+            int e1y = e1.a / width;
+            int e2x = e2.a % width;
+            int e2y = e2.a / width;
+            int e3x = e3.a % width;
+            int e3y = e3.a / width;
+
+            if ((e1x == e2x && e2x == e3x && e1x == e3x)
+            ||  (e1y == e2y && e2y == e3y && e1y == e3y)) {
+                e1.next = e3;
+                e3.prev = e1;
+                e2 = e3;
+                e3 = e2.next;
+                count = 0;
+                --length;
+            }
+            else {
+                e1 = e1.next;
+                e2 = e2.next;
+                e3 = e3.next;
+                ++count;
+            }
+        }
+        while (count < length + 2);
+
+        return e1;
+    }
+
+    protected int []            raster;
+    protected int               width;
+    protected TIntObjectHashMap openEdges;
+    protected ArrayList         rings;
+
+    public Vectorizer() {
+        openEdges = new TIntObjectHashMap();
+        rings     = new ArrayList();
+    }
+
+    public Vectorizer(int [] raster, int width) {
+        this();
+        this.raster = raster;
+        this.width  = width;
+    }
+
+    public static final int tl(int i, int w) {
+        int x = i % w;
+        int y = i / w;
+        return x + (w + 1)*y;
+    }
+
+    public static final int tr(int i, int w) {
+        return tl(i, w) + 1;
+    }
+
+    public static final int bl(int i, int w) {
+        return tl(i, w) + w + 1;
+    }
+
+    public static final int br(int i, int w) {
+        return bl(i, w) + 1;
+    }
+
+    protected void resetRegion() {
+        openEdges.clear();
+        rings.clear();
+    }
+
+    protected void emit(Edge edge) {
+
+        Edge otherA = (Edge)openEdges.remove(edge.a);
+
+        if (otherA != null) {
+            otherA.chain(edge, edge.a);
+        }
+
+        Edge otherB = (Edge)openEdges.remove(edge.b);
+        if (otherB != null) {
+            otherB.chain(edge, edge.b);
+        }
+
+        if (edge.isComplete()) {
+            rings.add(simplify(edge, width + 1));
+        }
+        else {
+            if (otherA == null) {
+                openEdges.put(edge.a, edge);
+            }
+            if (otherB == null) {
+                openEdges.put(edge.b, edge);
+            }
+        }
+    }
+
+    public int process(RingsHandler handler) {
+
+        BitSet visited = new BitSet(raster.length);
+
+        TIntStack stack = new TIntStack();
+
+        int regions = 0;
+
+
+        for (int i = 0; i < raster.length; ++i) {
+            if (visited.get(i)) {
+                continue;
+            }
+
+            ++regions;
+
+            int currentValue = raster[i];
+            visited.set(i);
+
+            int current = i;
+            visited.set(current);
+
+            for (;;) {
+                int tl = tl(current, width);
+                int tr = tr(current, width);
+                int bl = bl(current, width);
+                int br = br(current, width);
+
+                int t = current - width;
+
+                if (t < 0) {
+                    emit(new Edge(tr, tl));
+                }
+                else {
+                    if (raster[t] != currentValue) {
+                        emit(new Edge(tr, tl));
+                    }
+                    else {
+                        if (!visited.get(t)) {
+                            visited.set(t);
+                            stack.push(t);
+                        }
+                    }
+                }
+
+                int b = current + width;
+
+                if (b >= raster.length) {
+                    emit(new Edge(bl, br));
+                }
+                else {
+                    if (raster[b] != currentValue) {
+                        emit(new Edge(bl, br));
+                    }
+                    else {
+                        if (!visited.get(b)) {
+                            visited.set(b);
+                            stack.push(b);
+                        }
+                    }
+                }
+
+                int x = current % width;
+
+                if (x == 0) {
+                    emit(new Edge(tl, bl));
+                }
+                else {
+                    int l = current - 1;
+                    if (raster[l] != currentValue) {
+                        emit(new Edge(tl, bl));
+                    }
+                    else {
+                        if (!visited.get(l)) {
+                            visited.set(l);
+                            stack.push(l);
+                        }
+                    }
+                }
+
+                if (x == width - 1) {
+                    emit(new Edge(br, tr));
+                }
+                else {
+                    int r = current + 1;
+                    if (raster[r] != currentValue) {
+                        emit(new Edge(br, tr));
+                    }
+                    else {
+                        if (!visited.get(r)) {
+                            visited.set(r);
+                            stack.push(r);
+                        }
+                    }
+                }
+
+                if (stack.size() == 0) {
+                    break;
+                }
+
+                current = stack.pop();
+            }
+
+            handler.handleRings(rings, currentValue, width + 1);
+
+            resetRegion();
+        }
+
+        return regions;
+    }
+}
+// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8: