Tile computation

2 files changed, 119 insertions, 0 deletions

diff --git a/main/src/cgeo/geocaching/connector/gc/Tile.java b/main/src/cgeo/geocaching/connector/gc/Tile.java
new file mode 100644
index 0000000..f036f59
--- /dev/null
+++ b/main/src/cgeo/geocaching/connector/gc/Tile.java
@@ -0,0 +1,86 @@
+package cgeo.geocaching.connector.gc;
+
+import cgeo.geocaching.geopoint.Geopoint;
+
+/**
+ * All about tiles.
+ *
+ * @author blafoo
+ *
+ * @see http://msdn.microsoft.com/en-us/library/bb259689.aspx
+ * @see http
+ *      ://svn.openstreetmap.org/applications/viewer/jmapviewer/src/org/openstreetmap/gui/jmapviewer/OsmMercator.java
+ */
+public class Tile {
+
+    public static final int TILE_SIZE = 256;
+
+    private final int tileX;
+    private final int tileY;
+    private final int zoomlevel;
+    private final int numberOfTiles;
+
+    public Tile(Geopoint origin, int zoomlevel) {
+        this.zoomlevel = zoomlevel;
+        numberOfTiles = 1 << zoomlevel;
+        tileX = calcX(origin);
+        tileY = calcY(origin);
+    }
+
+    public Tile(int tileX, int tileY, int zoomlevel) {
+        this.zoomlevel = zoomlevel;
+        numberOfTiles = 1 << zoomlevel;
+        this.tileX = tileX;
+        this.tileY = tileY;
+    }
+
+    public long getZoomlevel() {
+        return zoomlevel;
+    }
+
+    /**
+     * Calculate the tile for a Geopoint based on the Spherical Mercator.
+     *
+     * @see http://developers.cloudmade.com/projects/tiles/examples/convert-coordinates-to-tile-numbers
+     */
+    private int calcX(final Geopoint origin) {
+        return (int) ((origin.getLongitude() + 180.0) / 360.0 * numberOfTiles);
+    }
+
+    public int getX() {
+        return tileX;
+    }
+
+    public int getY() {
+        return tileY;
+    }
+
+    /**
+     * Calculate the tile for a Geopoint based on the Spherical Mercator.
+     *
+     * @see http://developers.cloudmade.com/projects/tiles/examples/convert-coordinates-to-tile-numbers
+     */
+    private int calcY(final Geopoint origin) {
+        double lat_rad = Math.toRadians(origin.getLatitude());
+
+        return (int) ((1 - (Math.log(Math.tan(lat_rad) + (1 / Math.cos(lat_rad))) / Math.PI)) / 2 * numberOfTiles);
+    }
+
+    /** Calculate latitude/longitude for a given x/y position in this tile. */
+    public Geopoint getCoord(UTFGridPosition pos) {
+
+        long numberOfPixels = TILE_SIZE * numberOfTiles;
+
+        double pixX = tileX * TILE_SIZE + pos.x * 4;
+        double pixY = tileY * TILE_SIZE + pos.y * 4;
+
+        pixY += -1 * numberOfPixels / 2;
+        double radius = numberOfPixels / (2.0 * Math.PI);
+        double lat = (Math.PI / 2) - (2 * Math.atan(Math.exp(-1.0 * pixY / radius)));
+        lat = -1 * Math.toDegrees(lat);
+
+        double lon = ((360.0 * pixX) / numberOfPixels) - 180.0;
+        return new Geopoint(lat, lon);
+    }
+
+}
diff --git a/main/src/cgeo/geocaching/connector/gc/UTFGridPosition.java b/main/src/cgeo/geocaching/connector/gc/UTFGridPosition.java
new file mode 100644
index 0000000..cbd7696
--- /dev/null
+++ b/main/src/cgeo/geocaching/connector/gc/UTFGridPosition.java
@@ -0,0 +1,33 @@
+package cgeo.geocaching.connector.gc;
+
+/**
+ * Representation of a position inside an UTFGrid
+ *
+ * @author blafoo
+ *
+ */
+public final class UTFGridPosition {
+
+    public final int x;
+    public final int y;
+
+    UTFGridPosition(final int x, final int y) {
+        if (x > UTFGrid.GRID_MAXX) {
+            throw new IllegalArgumentException("x outside grid");
+        }
+        if (y > UTFGrid.GRID_MAXY) {
+            throw new IllegalArgumentException("y outside grid");
+        }
+        this.x = x;
+        this.y = y;
+    }
+
+    public int getX() {
+        return x;
+    }
+
+    public int getY() {
+        return y;
+    }
+
+}