Feature branch for tiles xy-to-quadkey conversion

pom.xml

@@ -25,6 +25,11 @@
             <artifactId>junit</artifactId>
             <version>4.1</version>
         </dependency>
+        <dependency>
+            <groupId>com.vividsolutions</groupId>
+            <artifactId>jts</artifactId>
+            <version>1.13</version>
+        </dependency>
     </dependencies>
      <build>
         <plugins>

src/main/java/de/rondiplomatico/nds/NDSBBox.java

@@ -30,6 +30,14 @@ public class NDSBBox {
     private final int south;
     private final int west;
 
+    // constructor to get global bounding box in NDS coordinates
+    public NDSBBox() {
+    	north =   90;
+    	east  =  180;
+    	south =  -90;
+    	west  = -180;
+    }
+
     /**
      * 
      * Gets the south west corner of the bounding box

src/main/java/de/rondiplomatico/nds/NDSCoordinate.java

@@ -96,6 +96,21 @@ public NDSCoordinate(long ndsMortonCoordinates) {
         latitude = lat;
         longitude = lon;
     }
+
+    /*
+     * Compute midpoint of this and given NDSCoordinate
+     * 
+     * @param p
+     *          the given coordinate
+     */
+    public NDSCoordinate getMidpoint(NDSCoordinate p) {
+        double lat                          = p.toWGS84().getLatitude();
+        double lon                          = p.toWGS84().getLongitude();
+        WGS84Coordinate lonlat              = toWGS84();
+        double longitude                    = lonlat.getLongitude();
+        double latitude                     = lonlat.getLatitude();
+        return new NDSCoordinate(longitude + 0.5 * (lon - longitude), latitude + 0.5 * (lat - latitude));
+    }
 
     private void verify(int lon, int lat) {
         if (lat < MIN_LATITUDE || MAX_LATITUDE < lat) {

src/main/java/de/rondiplomatico/nds/NDSEnvelope.java

@@ -0,0 +1,86 @@
+package de.rondiplomatico.nds;
+
+import com.vividsolutions.jts.geom.Coordinate;
+import com.vividsolutions.jts.geom.OctagonalEnvelope;
+
+/**
+ * Class to get a vividsolutions envelope of coordinates.
+ * 
+ * No warranties for correctness, use at own risk.
+ * 
+ * @author Andreas Hessenthaler
+ * @since 13.02.2020
+ */
+public class NDSEnvelope {
+
+    private static OctagonalEnvelope vividEnvelope  = new OctagonalEnvelope();
+
+    public NDSEnvelope(double[][] polygonCoordinates) {
+        for(int i = 0; i < polygonCoordinates.length; i++) {
+            Coordinate vividCoord           = new Coordinate(polygonCoordinates[i][0], polygonCoordinates[i][1]);
+            vividEnvelope.expandToInclude(vividCoord);
+        }
+    }
+
+    public NDSEnvelope(OctagonalEnvelope e) {
+        vividEnvelope                       = e;
+    }
+
+    public OctagonalEnvelope getEnvelope() {
+        return vividEnvelope;
+    }
+
+    public NDSCoordinate getSouthWest() {
+        return new NDSCoordinate(vividEnvelope.getMinX(), vividEnvelope.getMinY());
+    }
+
+    public NDSCoordinate getSouthEast() {
+        return new NDSCoordinate(vividEnvelope.getMaxX(), vividEnvelope.getMinY());
+    }
+
+    public NDSCoordinate getNorthEast() {
+        return new NDSCoordinate(vividEnvelope.getMinX(), vividEnvelope.getMaxY());
+    }
+
+    public NDSCoordinate getNorthWest() {
+        return new NDSCoordinate(vividEnvelope.getMaxX(), vividEnvelope.getMaxY());
+    }
+
+    public int[] getMasterTileInfo(int maxLevels) {
+        NDSCoordinate point0                = getSouthWest();
+        NDSCoordinate point1                = getSouthEast();
+        NDSCoordinate point2                = getNorthEast();
+        NDSCoordinate point3                = getNorthWest();
+        return getMasterTileInfo(point0, point1, point2, point3, maxLevels);
+    }
+
+    public int[] getMasterTileInfo(NDSCoordinate point0, NDSCoordinate point1, NDSCoordinate point2, NDSCoordinate point3, int maxLevels) {
+        int masterTileLevel                 = -1;
+        int masterTileID                    = -1;
+        for (int li = 0; li < maxLevels; li++) {
+            NDSTile currTile0               = new NDSTile(li, point0);
+            NDSTile currTile1               = new NDSTile(li, point1);
+            NDSTile currTile2               = new NDSTile(li, point2);
+            NDSTile currTile3               = new NDSTile(li, point3);
+            int currTileID0                 = currTile0.getTileNumber();
+            int currTileID1                 = currTile1.getTileNumber();
+            int currTileID2                 = currTile2.getTileNumber();
+            int currTileID3                 = currTile3.getTileNumber();
+            boolean singleTileID            = (currTileID0 == currTileID1) && (currTileID0 == currTileID2) && (currTileID0 == currTileID3);
+            // if at least one tile ID is different, we discard the tile IDs and keep our previously detected tile ID (i.e. on the previous level)
+            if(!singleTileID) {
+                break;
+            }
+            // store tile info
+            masterTileLevel                 = li;
+            masterTileID                    = currTileID0;
+        }
+        // check if valid result
+        if (masterTileID == -1) {
+            System.out.println(">>>ERROR: Invalid master tile ID.");
+            System.exit(1);
+        }
+        int[] masterTileInfo                = {masterTileLevel, masterTileID};
+        return masterTileInfo;
+    }
+}