Index: trunk/src/org/openstreetmap/josm/data/projection/BelgianLambert1972.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/projection/BelgianLambert1972.java	(revision 5071)
+++ trunk/src/org/openstreetmap/josm/data/projection/BelgianLambert1972.java	(revision 5072)
@@ -1,2 +1,3 @@
+// License: GPL. For details, see LICENSE file.
 package org.openstreetmap.josm.data.projection;
 
Index: trunk/src/org/openstreetmap/josm/data/projection/BelgianLambert2008.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/projection/BelgianLambert2008.java	(revision 5071)
+++ trunk/src/org/openstreetmap/josm/data/projection/BelgianLambert2008.java	(revision 5072)
@@ -1,2 +1,3 @@
+// License: GPL. For details, see LICENSE file.
 package org.openstreetmap.josm.data.projection;
 
Index: trunk/src/org/openstreetmap/josm/data/projection/CustomProjection.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/projection/CustomProjection.java	(revision 5072)
+++ trunk/src/org/openstreetmap/josm/data/projection/CustomProjection.java	(revision 5072)
@@ -0,0 +1,351 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.data.projection;
+
+import static org.openstreetmap.josm.tools.I18n.tr;
+
+import java.awt.GridBagLayout;
+import java.awt.event.ActionListener;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import javax.swing.JPanel;
+import javax.swing.JTextField;
+
+import org.openstreetmap.josm.data.Bounds;
+import org.openstreetmap.josm.data.coor.LatLon;
+import org.openstreetmap.josm.data.projection.datum.CentricDatum;
+import org.openstreetmap.josm.data.projection.datum.Datum;
+import org.openstreetmap.josm.data.projection.datum.SevenParameterDatum;
+import org.openstreetmap.josm.data.projection.datum.ThreeParameterDatum;
+import org.openstreetmap.josm.data.projection.proj.Proj;
+import org.openstreetmap.josm.data.projection.proj.ProjParameters;
+import org.openstreetmap.josm.tools.Utils;
+
+/**
+ * Custom projection
+ *
+ * Inspired by PROJ.4 and Proj4J.
+ */
+public class CustomProjection extends AbstractProjection implements ProjectionSubPrefs {
+
+    private String pref = "";
+
+    public void update(String pref) {
+        try {
+            Map<String, String> parameters = new HashMap<String, String>();
+            String[] parts = pref.trim().split("\\s+");
+            for (int i = 0; i < parts.length; i++) {
+                String part = parts[i];
+                if (part.charAt(0) != '+')
+                    throw new ProjectionConfigurationException(tr("Parameter must begin with a ''+'' sign (found ''{0}'')", part));
+                Matcher m = Pattern.compile("\\+([a-zA-Z0-9_]+)(=(.*))?").matcher(part);
+                if (m.matches()) {
+                    String key = m.group(1);
+                    String value = null;
+                    if (m.groupCount() >= 3) {
+                        value = m.group(3);
+                    }
+                    parameters.put(key, value);
+                } else
+                    throw new ProjectionConfigurationException(tr("Unexpected parameter format (''{0}'')", part));
+            }
+            ellps = parseEllipsoid(parameters);
+            datum = parseDatum(parameters, ellps);
+            proj = parseProjection(parameters, ellps);
+            String s = parameters.get("x_0");
+            if (s != null) {
+                this.x_0 = parseDouble(s, "x_0");
+            }
+            s = parameters.get("y_0");
+            if (s != null) {
+                this.y_0 = parseDouble(s, "y_0");
+            }
+            s = parameters.get("lon_0");
+            if (s != null) {
+                this.lon_0 = parseAngle(s, "lon_0");
+            }
+            s = parameters.get("k_0");
+            if (s != null) {
+                this.k_0 = parseDouble(s, "k_0");
+            }
+        } catch (ProjectionConfigurationException e) {
+            System.err.println(e.toString()); // FIXME
+        }
+        this.pref = pref;
+    }
+
+    public Ellipsoid parseEllipsoid(Map<String, String> parameters) throws ProjectionConfigurationException {
+        String code = parameters.get("ellps");
+        if (code != null) {
+            Ellipsoid ellipsoid = Projections.getEllipsoid(code);
+            if (ellipsoid == null) {
+                throw new ProjectionConfigurationException(tr("Ellipsoid ''{0}'' not supported.", code));
+            } else {
+                return ellipsoid;
+            }
+        }
+        String s = parameters.get("a");
+        if (s != null) {
+            double a = parseDouble(s, "a");
+            if (parameters.get("es") != null) {
+                double es = parseDouble(parameters, "es");
+                return Ellipsoid.create_a_es(a, es);
+            }
+            if (parameters.get("rf") != null) {
+                double rf = parseDouble(parameters, "rf");
+                return Ellipsoid.create_a_rf(a, rf);
+            }
+            if (parameters.get("f") != null) {
+                double f = parseDouble(parameters, "f");
+                return Ellipsoid.create_a_f(a, f);
+            }
+            if (parameters.get("b") != null) {
+                double b = parseDouble(parameters, "b");
+                return Ellipsoid.create_a_b(a, b);
+            }
+        }
+        if (parameters.containsKey("a") ||
+                parameters.containsKey("es") ||
+                parameters.containsKey("rf") ||
+                parameters.containsKey("f") ||
+                parameters.containsKey("b"))
+            throw new ProjectionConfigurationException(tr("Combination of ellipsoid parameters is not supported."));
+        // nothing specified, use WGS84 as default
+        return Ellipsoid.WGS84;
+    }
+
+    public Datum parseDatum(Map<String, String> parameters, Ellipsoid ellps) throws ProjectionConfigurationException {
+        String towgs84 = parameters.get("towgs84");
+        if (towgs84 != null)
+            return parseToWGS84(towgs84, ellps);
+
+        String datumId = parameters.get("datum");
+        if (datumId != null) {
+            Datum datum = Projections.getDatum(datumId);
+            if (datum == null) throw new ProjectionConfigurationException(tr("Unkown datum identifier: ''{0}''", datumId));
+            return datum;
+        } else
+            return new CentricDatum(null, null, ellps);
+    }
+
+    public Datum parseToWGS84(String paramList, Ellipsoid ellps) throws ProjectionConfigurationException {
+        String[] numStr = paramList.split(",");
+
+        if (numStr.length != 3 && numStr.length != 7)
+            throw new ProjectionConfigurationException(tr("Unexpected number of arguments for parameter ''towgs84'' (must be 3 or 7)"));
+        List<Double> towgs84Param = new ArrayList<Double>();
+        for (int i = 0; i < numStr.length; i++) {
+            try {
+                towgs84Param.add(Double.parseDouble(numStr[i]));
+            } catch (NumberFormatException e) {
+                throw new ProjectionConfigurationException(tr("Unable to parse value of parameter ''towgs84'' (''{0}'')", numStr[i]));
+            }
+        }
+        boolean is3Param = true;
+        for (int i = 3; i<towgs84Param.size(); i++) {
+            if (towgs84Param.get(i) != 0.0) {
+                is3Param = false;
+                break;
+            }
+        }
+        Datum datum = null;
+        if (is3Param) {
+            datum = new ThreeParameterDatum(null, null, ellps,
+                    towgs84Param.get(0),
+                    towgs84Param.get(1),
+                    towgs84Param.get(2)
+            );
+        } else {
+            datum = new SevenParameterDatum(null, null, ellps,
+                    towgs84Param.get(0),
+                    towgs84Param.get(1),
+                    towgs84Param.get(2),
+                    towgs84Param.get(3),
+                    towgs84Param.get(4),
+                    towgs84Param.get(5),
+                    towgs84Param.get(6)
+            );
+        }
+        return datum;
+    }
+
+    public Proj parseProjection(Map<String, String> parameters, Ellipsoid ellps) throws ProjectionConfigurationException {
+        String id = (String) parameters.get("proj");
+        if (id == null) throw new ProjectionConfigurationException(tr("Projection required (+proj=*)"));
+
+        Proj proj =  Projections.getProjection(id);
+        if (proj == null) throw new ProjectionConfigurationException(tr("Unkown projection identifier: ''{0}''", id));
+
+        ProjParameters projParams = new ProjParameters();
+
+        projParams.ellps = ellps;
+
+        String s;
+        s = parameters.get("lat_0");
+        if (s != null) {
+            projParams.lat_0 = parseAngle(s, "lat_0");
+        }
+        s = parameters.get("lat_1");
+        if (s != null) {
+            projParams.lat_1 = parseAngle(s, "lat_1");
+        }
+        s = parameters.get("lat_2");
+        if (s != null) {
+            projParams.lat_2 = parseAngle(s, "lat_2");
+        }
+        proj.initialize(projParams);
+        return proj;
+
+    }
+
+    public double parseDouble(Map<String, String> parameters, String parameterName) throws ProjectionConfigurationException {
+        String doubleStr = parameters.get(parameterName);
+        if (doubleStr == null && parameters.containsKey(parameterName))
+            throw new ProjectionConfigurationException(
+                    tr("Expected number argument for parameter ''{0}''", parameterName));
+        return parseDouble(doubleStr, parameterName);
+    }
+
+    public double parseDouble(String doubleStr, String parameterName) throws ProjectionConfigurationException {
+        try {
+            return Double.parseDouble(doubleStr);
+        } catch (NumberFormatException e) {
+            throw new ProjectionConfigurationException(
+                    tr("Unable to parse value of ''{0}'' parameter ''{0}'' as number.", parameterName, doubleStr));
+        }
+    }
+
+    public double parseAngle(String angleStr, String parameterName) throws ProjectionConfigurationException {
+        String s = angleStr;
+        double value = 0;
+        boolean neg = false;
+        Matcher m = Pattern.compile("^-").matcher(s);
+        if (m.find()) {
+            neg = true;
+            s = s.substring(m.end());
+        }
+        final String FLOAT = "(\\d+(\\.\\d*)?)";
+        boolean dms = false;
+        // degrees
+        m = Pattern.compile("^"+FLOAT+"d").matcher(s);
+        if (m.find()) {
+            s = s.substring(m.end());
+            value += Double.parseDouble(m.group(1));
+            dms = true;
+        }
+        // minutes
+        m = Pattern.compile("^"+FLOAT+"'").matcher(s);
+        if (m.find()) {
+            s = s.substring(m.end());
+            value += Double.parseDouble(m.group(1)) / 60.0;
+            dms = true;
+        }
+        // seconds
+        m = Pattern.compile("^"+FLOAT+"\"").matcher(s);
+        if (m.find()) {
+            s = s.substring(m.end());
+            value += Double.parseDouble(m.group(1)) / 3600.0;
+            dms = true;
+        }
+        // plain number (in degrees)
+        if (!dms) {
+            m = Pattern.compile("^"+FLOAT).matcher(s);
+            if (m.find()) {
+                s = s.substring(m.end());
+                value += Double.parseDouble(m.group(1));
+            }
+        }
+        m = Pattern.compile("^(N|E)", Pattern.CASE_INSENSITIVE).matcher(s);
+        if (m.find()) {
+            s = s.substring(m.end());
+        } else {
+            m = Pattern.compile("^(S|W)", Pattern.CASE_INSENSITIVE).matcher(s);
+            if (m.find()) {
+                s = s.substring(m.end());
+                neg = !neg;
+            }
+        }
+        if (neg) {
+            value = -value;
+        }
+        if (!s.isEmpty()) {
+            throw new ProjectionConfigurationException(
+                    tr("Unable to parse value of ''{0}'' parameter ''{0}'' as coordinate value.", parameterName, angleStr));
+        }
+        return value;
+    }
+
+    public void dump() {
+        System.err.println("x_0="+x_0);
+        System.err.println("y_0="+y_0);
+        System.err.println("lon_0="+lon_0);
+        System.err.println("k_0="+k_0);
+        System.err.println("ellps="+ellps);
+        System.err.println("proj="+proj);
+        System.err.println("datum="+datum);
+    }
+
+    @Override
+    public Integer getEpsgCode() {
+        return null;
+    }
+
+    @Override
+    public String toCode() {
+        return Utils.md5Hex(pref).substring(0, 10);
+    }
+
+    @Override
+    public String getCacheDirectoryName() {
+        return toCode();
+    }
+
+    @Override
+    public Bounds getWorldBoundsLatLon() {
+        return new Bounds(
+            new LatLon(-85.05112877980659, -180.0),
+            new LatLon(85.05112877980659, 180.0)); // FIXME
+    }
+
+    @Override
+    public String toString() {
+        return tr("Custom Projection (from PROJ.4 string)");
+    }
+
+    @Override
+    public void setupPreferencePanel(JPanel p, ActionListener listener) {
+        JTextField input = new JTextField(pref, 50);
+        p.setLayout(new GridBagLayout());
+        p.add(input);
+    }
+
+    @Override
+    public Collection<String> getPreferences(JPanel p) {
+        Object prefTf = p.getComponent(0);
+        if (!(prefTf instanceof JTextField))
+            return null;
+        String pref = ((JTextField) prefTf).getText();
+        return Collections.singleton(pref);
+    }
+
+    @Override
+    public void setPreferences(Collection<String> args) {
+        update(args.iterator().next());
+    }
+
+    @Override
+    public String[] allCodes() {
+        return new String[0];
+    }
+
+    @Override
+    public Collection<String> getPreferencesFromCode(String code) {
+        return null;
+    }
+
+}
Index: trunk/src/org/openstreetmap/josm/data/projection/Ellipsoid.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/projection/Ellipsoid.java	(revision 5071)
+++ trunk/src/org/openstreetmap/josm/data/projection/Ellipsoid.java	(revision 5072)
@@ -9,6 +9,4 @@
 
 import org.openstreetmap.josm.data.coor.LatLon;
-import java.util.List;
-import java.util.ArrayList;
 
 /**
@@ -127,4 +125,9 @@
     public static Ellipsoid create_a_rf(double a, double rf) {
         return create_a_f(a, 1.0 / rf);
+    }
+
+    @Override
+    public String toString() {
+        return "Ellipsoid{a="+a+", b="+b+"}";
     }
 
Index: trunk/src/org/openstreetmap/josm/data/projection/Projections.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/projection/Projections.java	(revision 5071)
+++ trunk/src/org/openstreetmap/josm/data/projection/Projections.java	(revision 5072)
@@ -4,8 +4,17 @@
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
 
 import org.openstreetmap.josm.Main;
 import org.openstreetmap.josm.data.coor.EastNorth;
 import org.openstreetmap.josm.data.coor.LatLon;
+import org.openstreetmap.josm.data.projection.datum.Datum;
+import org.openstreetmap.josm.data.projection.datum.WGS84Datum;
+import org.openstreetmap.josm.data.projection.proj.LambertConformalConic;
+import org.openstreetmap.josm.data.projection.proj.Proj;
+import org.openstreetmap.josm.data.projection.proj.SwissObliqueMercator;
+import org.openstreetmap.josm.data.projection.proj.TransverseMercator;
+import org.openstreetmap.josm.tools.CheckParameterUtil;
 
 /**
@@ -23,18 +32,24 @@
                 new Mercator(),
                 new UTM(),
-                // regional - alphabetical order by country name
-                new GaussKrueger(),
-                new BelgianLambert1972(),
-                new BelgianLambert2008(),
-                new LambertEST(),
-                new Lambert(),
-                new Lambert93(),
-                new LambertCC9Zones(),
-                new UTM_France_DOM(),
-                new TransverseMercatorLV(),
-                new Puwg(),
-                new Epsg3008(), // SWEREF99 13 30
-                new SwissGrid(),
+                // regional - alphabetical order by country code
+                new BelgianLambert1972(),   // BE
+                new BelgianLambert2008(),   // BE
+                new SwissGrid(),            // CH
+                new GaussKrueger(),         // DE
+                new LambertEST(),           // EE
+                new Lambert(),              // FR
+                new Lambert93(),            // FR
+                new LambertCC9Zones(),      // FR
+                new UTM_France_DOM(),       // FR
+                new TransverseMercatorLV(), // LV
+                new Puwg(),                 // PL
+                new Epsg3008(),             // SE
         }));
+
+    static {
+        if (Main.pref.getBoolean("customprojection")) {
+            addProjection(new CustomProjection());
+        }
+    }
 
     public static ArrayList<Projection> getProjections() {
@@ -44,5 +59,5 @@
     /**
      * Adds a new projection to the list of known projections.
-     * 
+     *
      * For Plugins authors: make sure your plugin is an early plugin, i.e. put
      * Plugin-Early=true in your Manifest.
@@ -52,12 +67,58 @@
     }
 
-    static public EastNorth project(LatLon ll) {
+    public static EastNorth project(LatLon ll) {
         if (ll == null) return null;
         return Main.getProjection().latlon2eastNorth(ll);
     }
 
-    static public LatLon inverseProject(EastNorth en) {
+    public static LatLon inverseProject(EastNorth en) {
         if (en == null) return null;
         return Main.getProjection().eastNorth2latlon(en);
     }
+
+    /*********************************
+     * Registry for custom projection
+     *
+     * should be compatible to PROJ.4
+     */
+
+    private static Map<String, Ellipsoid> ellipsoids = new HashMap<String, Ellipsoid>();
+    private static Map<String, Class<? extends Proj>> projs = new HashMap<String, Class<? extends Proj>>();
+    private static Map<String, Datum> datums = new HashMap<String, Datum>();
+
+    static {
+        ellipsoids.put("intl", Ellipsoid.hayford);
+        ellipsoids.put("GRS80", Ellipsoid.GRS80);
+        ellipsoids.put("WGS84", Ellipsoid.WGS84);
+        ellipsoids.put("bessel", Ellipsoid.Bessel1841);
+
+        projs.put("merc", org.openstreetmap.josm.data.projection.proj.Mercator.class);
+        projs.put("lcc", LambertConformalConic.class);
+        projs.put("somerc", SwissObliqueMercator.class);
+        projs.put("tmerc", TransverseMercator.class);
+
+        datums.put("WGS84", WGS84Datum.INSTANCE);
+    }
+
+    public static Ellipsoid getEllipsoid(String id) {
+        return ellipsoids.get(id);
+    }
+
+    public static Proj getProjection(String id) {
+        Class<? extends Proj> projClass = projs.get(id);
+        if (projClass == null) return null;
+        Proj proj = null;
+        try {
+            proj = projClass.newInstance();
+        } catch (InstantiationException e) {
+            throw new RuntimeException(e);
+        } catch (IllegalAccessException e) {
+            throw new RuntimeException(e);
+        }
+        return proj;
+    }
+
+    public static Datum getDatum(String id) {
+        return datums.get(id);
+    }
 }
Index: trunk/src/org/openstreetmap/josm/data/projection/datum/CentricDatum.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/projection/datum/CentricDatum.java	(revision 5071)
+++ trunk/src/org/openstreetmap/josm/data/projection/datum/CentricDatum.java	(revision 5072)
@@ -14,5 +14,5 @@
         super(name, proj4Id, ellps);
     }
-    
+
     @Override
     public LatLon toWGS84(LatLon ll) {
@@ -24,4 +24,8 @@
         return this.ellps.cart2LatLon(Ellipsoid.WGS84.latLon2Cart(ll));
     }
-    
+
+    @Override
+    public String toString() {
+        return "CentricDatum{ellipsoid="+ellps+"}";
+    }
 }