1 | // License: GPL. For details, see LICENSE file.
|
---|
2 | package org.openstreetmap.josm.data.coor;
|
---|
3 |
|
---|
4 | import org.openstreetmap.josm.tools.Utils;
|
---|
5 |
|
---|
6 | /**
|
---|
7 | * This class helps in tiling the world into multiple quad tiles.
|
---|
8 | */
|
---|
9 | public final class QuadTiling {
|
---|
10 |
|
---|
11 | private QuadTiling() {
|
---|
12 | // Hide default constructor for utils classes
|
---|
13 | }
|
---|
14 |
|
---|
15 | /**
|
---|
16 | * The maximum number of levels to split the quads
|
---|
17 | */
|
---|
18 | public static final int NR_LEVELS = 24;
|
---|
19 | /**
|
---|
20 | * The number of parts the world is split into in each direction
|
---|
21 | */
|
---|
22 | public static final double WORLD_PARTS = 1 << NR_LEVELS;
|
---|
23 |
|
---|
24 | /**
|
---|
25 | * The log(2) of how many tiles there are per level
|
---|
26 | */
|
---|
27 | public static final int TILES_PER_LEVEL_SHIFT = 2; // Has to be 2. Other parts of QuadBuckets code rely on it
|
---|
28 | /**
|
---|
29 | * How many tiles there are per level
|
---|
30 | */
|
---|
31 | public static final int TILES_PER_LEVEL = 1 << TILES_PER_LEVEL_SHIFT;
|
---|
32 | /**
|
---|
33 | * The size of the world in X direction
|
---|
34 | */
|
---|
35 | public static final int X_PARTS = 360;
|
---|
36 | /**
|
---|
37 | * The offset of the world in x direction
|
---|
38 | */
|
---|
39 | public static final int X_BIAS = -180;
|
---|
40 |
|
---|
41 | /**
|
---|
42 | * The size of the world in y direction
|
---|
43 | */
|
---|
44 | public static final int Y_PARTS = 180;
|
---|
45 | /**
|
---|
46 | * The offset of the world in y direction
|
---|
47 | */
|
---|
48 | public static final int Y_BIAS = -90;
|
---|
49 |
|
---|
50 | /**
|
---|
51 | * Converts a tile index to a lat/lon position
|
---|
52 | * @param quad The tile to convert
|
---|
53 | * @return The lat/lon position of that tile
|
---|
54 | */
|
---|
55 | public static LatLon tile2LatLon(long quad) {
|
---|
56 | // The world is divided up into X_PARTS,Y_PARTS.
|
---|
57 | // The question is how far we move for each bit being set.
|
---|
58 | // In the case of the top level, we move half of the world.
|
---|
59 | double xUnit = X_PARTS/2d;
|
---|
60 | double yUnit = Y_PARTS/2d;
|
---|
61 | long shift = (NR_LEVELS*2L)-2L;
|
---|
62 |
|
---|
63 | double x = 0;
|
---|
64 | double y = 0;
|
---|
65 | for (int i = 0; i < NR_LEVELS; i++) {
|
---|
66 | long bits = (quad >> shift) & 0x3;
|
---|
67 | // remember x is the MSB
|
---|
68 | if ((bits & 0x2) != 0) {
|
---|
69 | x += xUnit;
|
---|
70 | }
|
---|
71 | if ((bits & 0x1) != 0) {
|
---|
72 | y += yUnit;
|
---|
73 | }
|
---|
74 | xUnit /= 2;
|
---|
75 | yUnit /= 2;
|
---|
76 | shift -= 2;
|
---|
77 | }
|
---|
78 | x += X_BIAS;
|
---|
79 | y += Y_BIAS;
|
---|
80 | return new LatLon(y, x);
|
---|
81 | }
|
---|
82 |
|
---|
83 | static long lon2x(double lon) {
|
---|
84 | long ret = (long) ((lon + 180.0) * WORLD_PARTS / 360.0);
|
---|
85 | if (Utils.equalsEpsilon(ret, WORLD_PARTS)) {
|
---|
86 | ret--;
|
---|
87 | }
|
---|
88 | return ret;
|
---|
89 | }
|
---|
90 |
|
---|
91 | static long lat2y(double lat) {
|
---|
92 | long ret = (long) ((lat + 90.0) * WORLD_PARTS / 180.0);
|
---|
93 | if (Utils.equalsEpsilon(ret, WORLD_PARTS)) {
|
---|
94 | ret--;
|
---|
95 | }
|
---|
96 | return ret;
|
---|
97 | }
|
---|
98 |
|
---|
99 | /**
|
---|
100 | * Returns quad tiling index for given coordinates and level.
|
---|
101 | *
|
---|
102 | * @param lat latitude
|
---|
103 | * @param lon longitude
|
---|
104 | * @param level level
|
---|
105 | *
|
---|
106 | * @return quad tiling index for given coordinates and level.
|
---|
107 | * @since 6171
|
---|
108 | */
|
---|
109 | public static byte index(final double lat, final double lon, final int level) {
|
---|
110 | long x = lon2x(lon);
|
---|
111 | long y = lat2y(lat);
|
---|
112 | int shift = NR_LEVELS-level-1;
|
---|
113 | return (byte) ((x >> shift & 1) * 2 + (y >> shift & 1));
|
---|
114 | }
|
---|
115 | }
|
---|