88 lines
2.1 KiB
C++
88 lines
2.1 KiB
C++
#ifndef UTIL_TILES_HPP
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#define UTIL_TILES_HPP
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#include "util/coordinate.hpp"
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#include <boost/assert.hpp>
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#include <cmath>
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#include <tuple>
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// This is a port of the tilebelt algorithm https://github.com/mapbox/tilebelt
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namespace osrm
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{
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namespace util
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{
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namespace tiles
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{
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struct Tile
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{
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unsigned x;
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unsigned y;
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unsigned z;
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};
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namespace detail
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{
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// optimized for 32bit integers
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static constexpr unsigned MAX_ZOOM = 32;
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// Returns 1-indexed 1..32 of MSB if value > 0 or 0 if value == 0
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inline unsigned getMSBPosition(std::uint32_t value)
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{
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if (value == 0)
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return 0;
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std::uint8_t pos = 1;
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while (value >>= 1)
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pos++;
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return pos;
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}
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inline unsigned getBBMaxZoom(const Tile top_left, const Tile bottom_left)
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{
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auto x_xor = top_left.x ^ bottom_left.x;
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auto y_xor = top_left.y ^ bottom_left.y;
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auto lon_msb = detail::getMSBPosition(x_xor);
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auto lat_msb = detail::getMSBPosition(y_xor);
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return MAX_ZOOM - std::max(lon_msb, lat_msb);
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}
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}
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inline Tile pointToTile(const FloatLongitude lon, const FloatLatitude lat)
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{
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auto sin_lat = std::sin(static_cast<double>(lat) * M_PI / 180.);
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auto p2z = std::pow(2, detail::MAX_ZOOM);
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unsigned x = p2z * (static_cast<double>(lon) / 360. + 0.5);
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unsigned y = p2z * (0.5 - 0.25 * std::log((1 + sin_lat) / (1 - sin_lat)) / M_PI);
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return Tile{x, y, detail::MAX_ZOOM};
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}
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inline Tile getBBMaxZoomTile(const FloatLongitude min_lon,
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const FloatLatitude min_lat,
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const FloatLongitude max_lon,
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const FloatLatitude max_lat)
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{
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const auto top_left = pointToTile(min_lon, min_lat);
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const auto bottom_left = pointToTile(max_lon, max_lat);
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BOOST_ASSERT(top_left.z == detail::MAX_ZOOM);
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BOOST_ASSERT(bottom_left.z == detail::MAX_ZOOM);
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const auto max_zoom = detail::getBBMaxZoom(top_left, bottom_left);
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if (max_zoom == 0)
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{
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return Tile{0, 0, 0};
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}
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auto x = top_left.x >> (detail::MAX_ZOOM - max_zoom);
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auto y = top_left.y >> (detail::MAX_ZOOM - max_zoom);
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return Tile{x, y, max_zoom};
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}
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}
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}
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}
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#endif
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