Index: /trunk/src/org/openstreetmap/josm/gui/download/DownloadDialog.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/download/DownloadDialog.java	(revision 978)
+++ /trunk/src/org/openstreetmap/josm/gui/download/DownloadDialog.java	(revision 979)
@@ -88,4 +88,5 @@
 		// predefined download selections
 		downloadSelections.add(new BoundingBoxSelection());
+		downloadSelections.add(new TileSelection());
 		downloadSelections.add(new BookmarkSelection());
 		downloadSelections.add(new WorldChooser());
Index: /trunk/src/org/openstreetmap/josm/gui/download/TileSelection.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/download/TileSelection.java	(revision 979)
+++ /trunk/src/org/openstreetmap/josm/gui/download/TileSelection.java	(revision 979)
@@ -0,0 +1,124 @@
+// License: GPL. See LICENSE file for details.
+package org.openstreetmap.josm.gui.download;
+
+import static org.openstreetmap.josm.tools.I18n.tr;
+
+import java.awt.Dimension;
+import java.awt.GridBagLayout;
+import java.awt.event.FocusAdapter;
+import java.awt.event.FocusEvent;
+import java.awt.event.FocusListener;
+
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.JSpinner;
+import javax.swing.JTextField;
+import javax.swing.SpinnerNumberModel;
+
+import org.openstreetmap.josm.tools.GBC;
+/**
+ * Tile selector.
+ * 
+ * Provides a tile coordinate input field.
+ * 
+ * @author Frederik Ramm <frederik@remote.org>
+ *
+ */
+public class TileSelection implements DownloadSelection {
+
+	private JTextField tileX0 = new JTextField(7);
+	private JTextField tileY0 = new JTextField(7);
+	private JTextField tileX1 = new JTextField(7);
+	private JTextField tileY1 = new JTextField(7);
+	private JSpinner tileZ = new JSpinner(new SpinnerNumberModel(12, 10, 18, 1));
+	
+	public void addGui(final DownloadDialog gui) {
+
+		JPanel smpanel = new JPanel(new GridBagLayout());
+		smpanel.add(new JLabel(tr("zoom level")), GBC.std().insets(0,0,10,0));
+		smpanel.add(new JLabel(tr("x from")), GBC.std().insets(10,0,5,0));
+		smpanel.add(tileX0, GBC.std());
+		smpanel.add(new JLabel(tr("to")), GBC.std().insets(10,0,5,0));
+		smpanel.add(tileX1, GBC.eol());
+		smpanel.add(tileZ, GBC.std().insets(0,0,10,0));
+		smpanel.add(new JLabel(tr("y from")), GBC.std().insets(10,0,5,0));
+		smpanel.add(tileY0, GBC.std());
+		smpanel.add(new JLabel(tr("to")), GBC.std().insets(10,0,5,0));
+		smpanel.add(tileY1, GBC.eol());
+
+		final FocusListener dialogUpdater = new FocusAdapter() {
+			@Override public void focusLost(FocusEvent e) {
+				try {
+					int zoomlvl = (Integer) tileZ.getValue();
+					int fromx = Integer.parseInt(tileX0.getText());
+					int tox = fromx;
+					if (tileX1.getText().length()>0) {
+						tox = Integer.parseInt(tileX1.getText());
+					}
+					if (tox<fromx) { int i = fromx; fromx=tox; tox=i; }
+
+					int fromy = Integer.parseInt(tileY0.getText());
+					int toy = fromy;
+					if (tileY1.getText().length()>0) {
+						toy = Integer.parseInt(tileY1.getText());
+					}
+					if (toy<fromy) { int i = fromy; fromy=toy; toy=i; }
+
+					gui.minlat = tileYToLat(zoomlvl, toy+1);
+					gui.minlon = tileXToLon(zoomlvl, fromx);
+					gui.maxlat = tileYToLat(zoomlvl, fromy);
+					gui.maxlon = tileXToLon(zoomlvl, tox+1);
+					gui.boundingBoxChanged(TileSelection.this);
+					//repaint();
+				} catch (NumberFormatException x) {
+					// ignore
+				}
+			}
+		};
+		
+		for (JTextField f : new JTextField[] { tileX0, tileX1, tileY0, tileY1 }) {
+			f.setMinimumSize(new Dimension(100,new JTextField().getMinimumSize().height));
+			f.addFocusListener(dialogUpdater);
+		}
+
+		gui.tabpane.addTab(tr("Tile Numbers"), smpanel);
+	}
+	
+	/**
+	 * Called when bounding box is changed by one of the other download dialog tabs.
+	 */
+	public void boundingBoxChanged(DownloadDialog gui) {
+		updateBboxFields(gui);
+	}
+	
+	private void updateBboxFields(DownloadDialog gui) {
+		int z = ((Integer) tileZ.getValue()).intValue();
+		tileX0.setText(Integer.toString(lonToTileX(z, gui.minlon)));
+		tileX1.setText(Integer.toString(lonToTileX(z, gui.maxlon-.00001)));
+		tileY0.setText(Integer.toString(latToTileY(z, gui.maxlat-.00001)));
+		tileY1.setText(Integer.toString(latToTileY(z, gui.minlat)));
+	}
+	
+	public static int latToTileY(int zoom, double lat) {
+		if ((zoom < 3) || (zoom > 18)) return -1; 
+		double l = lat / 180 * Math.PI;
+		double pf = Math.log(Math.tan(l) + (1/Math.cos(l)));
+		return (int) ((1<<(zoom-1)) * (Math.PI - pf) / Math.PI);
+	}   
+
+	public static int lonToTileX(int zoom, double lon) {
+		if ((zoom < 3) || (zoom > 18)) return -1; 
+		return (int) ((1<<(zoom-3)) * (lon + 180.0) / 45.0);
+	}
+
+	public static double tileYToLat(int zoom, int y) {
+		if ((zoom < 3) || (zoom > 18)) return Double.MIN_VALUE;
+		return Math.atan(Math.sinh(Math.PI - (Math.PI*y / (1<<(zoom-1))))) * 180 / Math.PI;
+	}
+
+	public static double tileXToLon(int zoom, int x) {
+		if ((zoom < 3) || (zoom > 18)) return Double.MIN_VALUE;
+		return x * 45.0 / (1<<(zoom-3)) - 180.0;
+
+	}
+}