001// License: GPL. For details, see LICENSE file. 002package org.openstreetmap.josm.data.coor; 003 004import org.openstreetmap.josm.tools.Utils; 005 006public final class QuadTiling { 007 008 private QuadTiling() { 009 // Hide default constructor for utils classes 010 } 011 012 public static final int NR_LEVELS = 24; 013 public static final double WORLD_PARTS = 1 << NR_LEVELS; 014 015 public static final int TILES_PER_LEVEL_SHIFT = 2; // Has to be 2. Other parts of QuadBuckets code rely on it 016 public static final int TILES_PER_LEVEL = 1 << TILES_PER_LEVEL_SHIFT; 017 public static final int X_PARTS = 360; 018 public static final int X_BIAS = -180; 019 020 public static final int Y_PARTS = 180; 021 public static final int Y_BIAS = -90; 022 023 public static LatLon tile2LatLon(long quad) { 024 // The world is divided up into X_PARTS,Y_PARTS. 025 // The question is how far we move for each bit being set. 026 // In the case of the top level, we move half of the world. 027 double xUnit = X_PARTS/2d; 028 double yUnit = Y_PARTS/2d; 029 long shift = (NR_LEVELS*2L)-2L; 030 031 double x = 0; 032 double y = 0; 033 for (int i = 0; i < NR_LEVELS; i++) { 034 long bits = (quad >> shift) & 0x3; 035 // remember x is the MSB 036 if ((bits & 0x2) != 0) { 037 x += xUnit; 038 } 039 if ((bits & 0x1) != 0) { 040 y += yUnit; 041 } 042 xUnit /= 2; 043 yUnit /= 2; 044 shift -= 2; 045 } 046 x += X_BIAS; 047 y += Y_BIAS; 048 return new LatLon(y, x); 049 } 050 051 static long lon2x(double lon) { 052 long ret = (long) ((lon + 180.0) * WORLD_PARTS / 360.0); 053 if (Utils.equalsEpsilon(ret, WORLD_PARTS)) { 054 ret--; 055 } 056 return ret; 057 } 058 059 static long lat2y(double lat) { 060 long ret = (long) ((lat + 90.0) * WORLD_PARTS / 180.0); 061 if (Utils.equalsEpsilon(ret, WORLD_PARTS)) { 062 ret--; 063 } 064 return ret; 065 } 066 067 /** 068 * Returns quad tiling index for given coordinates and level. 069 * 070 * @param lat latitude 071 * @param lon longitude 072 * @param level level 073 * 074 * @return quad tiling index for given coordinates and level. 075 * @since 6171 076 */ 077 public static int index(final double lat, final double lon, final int level) { 078 long x = lon2x(lon); 079 long y = lat2y(lat); 080 int shift = NR_LEVELS-level-1; 081 return (int) ((x >> shift & 1) * 2 + (y >> shift & 1)); 082 } 083}