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1 | /* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 4; tab-width: 4 -*- */ |
2 | /* | |
3 | * viking -- GPS Data and Topo Analyzer, Explorer, and Manager | |
4 | * | |
5ff65f40 | 5 | * Copyright (C) 2013-2014, Rob Norris <rw_norris@hotmail.com> |
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6 | * |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License as published by | |
9 | * the Free Software Foundation; either version 2 of the License, or | |
10 | * (at your option) any later version. | |
11 | * | |
12 | * This program is distributed in the hope that it will be useful, | |
13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | * GNU General Public License for more details. | |
16 | * | |
17 | * You should have received a copy of the GNU General Public License | |
18 | * along with this program; if not, write to the Free Software | |
19 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
20 | * | |
21 | */ | |
22 | #include "maputils.h" | |
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23 | #include "globals.h" |
24 | #include <math.h> | |
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25 | |
26 | // World Scale: VIK_GZ(17) | |
27 | // down to | |
28 | // Submeter scale: 1/VIK_GZ(5) | |
29 | // No map provider is going to have tiles at the highest zoom in level - but we can interpolate to that. | |
30 | ||
31 | static const gdouble scale_mpps[] = { VIK_GZ(0), VIK_GZ(1), VIK_GZ(2), VIK_GZ(3), VIK_GZ(4), VIK_GZ(5), | |
32 | VIK_GZ(6), VIK_GZ(7), VIK_GZ(8), VIK_GZ(9), VIK_GZ(10), VIK_GZ(11), | |
33 | VIK_GZ(12), VIK_GZ(13), VIK_GZ(14), VIK_GZ(15), VIK_GZ(16), VIK_GZ(17) }; | |
34 | static const gint num_scales = (sizeof(scale_mpps) / sizeof(scale_mpps[0])); | |
35 | ||
36 | static const gdouble scale_neg_mpps[] = { 1.0/VIK_GZ(0), 1.0/VIK_GZ(1), 1.0/VIK_GZ(2), | |
37 | 1.0/VIK_GZ(3), 1.0/VIK_GZ(4), 1.0/VIK_GZ(5) }; | |
38 | static const gint num_scales_neg = (sizeof(scale_neg_mpps) / sizeof(scale_neg_mpps[0])); | |
39 | ||
40 | #define ERROR_MARGIN 0.01 | |
41 | /** | |
42 | * map_utils_mpp_to_scale: | |
43 | * @mpp: The so called 'mpp' | |
44 | * | |
45 | * Returns: the zoom scale value which may be negative. | |
46 | */ | |
47 | gint map_utils_mpp_to_scale ( gdouble mpp ) { | |
48 | gint i; | |
49 | for ( i = 0; i < num_scales; i++ ) { | |
50 | if ( ABS(scale_mpps[i] - mpp) < ERROR_MARGIN ) { | |
51 | return i; | |
52 | } | |
53 | } | |
54 | for ( i = 0; i < num_scales_neg; i++ ) { | |
55 | if ( ABS(scale_neg_mpps[i] - mpp) < 0.000001 ) { | |
56 | return -i; | |
57 | } | |
58 | } | |
59 | ||
60 | return 255; | |
61 | } | |
62 | ||
63 | /** | |
64 | * map_utils_mpp_to_zoom_level: | |
65 | * @mpp: The so called 'mpp' | |
66 | * | |
67 | * Returns: a Zoom Level | |
68 | * See: http://wiki.openstreetmap.org/wiki/Zoom_levels | |
69 | */ | |
70 | guint8 map_utils_mpp_to_zoom_level ( gdouble mpp ) | |
71 | { | |
72 | gint answer = 17 - map_utils_mpp_to_scale ( mpp ); | |
73 | if ( answer < 0 ) | |
74 | answer = 17; | |
75 | return answer; | |
76 | } | |
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77 | |
78 | /** | |
79 | * SECTION:maputils | |
80 | * @short_description: Notes about TMS / Spherical Mercator conversion | |
81 | * | |
82 | * VikCoords are in Spherical Mercator projection (#VIK_COORD_LATLON) | |
83 | * MapCoords are in Inverse TMS | |
84 | * | |
85 | * See: http://docs.openlayers.org/library/spherical_mercator.html | |
86 | * See: http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification | |
87 | * NB: the Y axis is inverted, ie the origin is at top-left corner. | |
88 | */ | |
89 | ||
90 | /** | |
91 | * map_utils_vikcoord_to_iTMS: | |
92 | * @src: Original #VikCoord in #VIK_COORD_LATLON format | |
93 | * @xzoom: Viking zoom level in x direction | |
94 | * @yzoom: Viking zoom level in y direction (actually needs to be same as xzoom) | |
95 | * @dest: The resulting Inverse TMS coordinates in #MapCoord | |
96 | * | |
97 | * Convert a #VikCoord in VIK_COORD_LATLON format into Inverse TMS coordinates | |
98 | * | |
99 | * Returns: whether the conversion was performed | |
100 | */ | |
101 | gboolean map_utils_vikcoord_to_iTMS ( const VikCoord *src, gdouble xzoom, gdouble yzoom, MapCoord *dest ) | |
102 | { | |
103 | if ( src->mode != VIK_COORD_LATLON ) | |
104 | return FALSE; | |
105 | ||
106 | if ( xzoom != yzoom ) | |
107 | return FALSE; | |
108 | ||
109 | dest->scale = map_utils_mpp_to_scale ( xzoom ); | |
110 | if ( dest->scale == 255 ) | |
111 | return FALSE; | |
112 | ||
113 | dest->x = (src->east_west + 180) / 360 * VIK_GZ(17) / xzoom; | |
114 | dest->y = (180 - MERCLAT(src->north_south)) / 360 * VIK_GZ(17) / xzoom; | |
115 | dest->z = 0; | |
116 | ||
117 | return TRUE; | |
118 | } | |
119 | ||
120 | // Internal convenience function | |
121 | static void _to_vikcoord_with_offset ( const MapCoord *src, VikCoord *dest, gdouble offset ) | |
122 | { | |
123 | gdouble socalled_mpp; | |
124 | if (src->scale >= 0) | |
125 | socalled_mpp = VIK_GZ(src->scale); | |
126 | else | |
127 | socalled_mpp = 1.0/VIK_GZ(-src->scale); | |
128 | dest->mode = VIK_COORD_LATLON; | |
129 | dest->east_west = ((src->x+offset) / VIK_GZ(17) * socalled_mpp * 360) - 180; | |
130 | dest->north_south = DEMERCLAT(180 - ((src->y+offset) / VIK_GZ(17) * socalled_mpp * 360)); | |
131 | } | |
132 | ||
133 | /** | |
134 | * map_utils_iTMS_to_center_vikcoord: | |
135 | * @src: Original #MapCoord in Inverse TMS format | |
136 | * @dest: The resulting Spherical Mercator coordinates in #VikCoord | |
137 | * | |
138 | * Convert a #MapCoord in Inverse TMS format into Spherical Mercator coordinates for the center of the TMS area | |
139 | * | |
140 | * Returns: whether the conversion was performed | |
141 | */ | |
142 | void map_utils_iTMS_to_center_vikcoord ( const MapCoord *src, VikCoord *dest ) | |
143 | { | |
144 | _to_vikcoord_with_offset ( src, dest, 0.5 ); | |
145 | } | |
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146 | |
147 | /** | |
148 | * map_utils_iTMS_to_vikcoord: | |
149 | * @src: Original #MapCoord in Inverse TMS format | |
150 | * @dest: The resulting Spherical Mercator coordinates in #VikCoord | |
151 | * | |
152 | * Convert a #MapCoord in Inverse TMS format into Spherical Mercator coordinates | |
153 | * (for the top left corner of the Inverse TMS area) | |
154 | * | |
155 | * Returns: whether the conversion was performed | |
156 | */ | |
157 | void map_utils_iTMS_to_vikcoord ( const MapCoord *src, VikCoord *dest ) | |
158 | { | |
159 | _to_vikcoord_with_offset ( src, dest, 0.0 ); | |
160 | } |