104 lines
4.2 KiB
C++
104 lines
4.2 KiB
C++
#pragma once
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#include <mbgl/util/constants.hpp>
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#include <mbgl/util/geo.hpp>
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#include <mbgl/util/geometry.hpp>
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#include <mbgl/math/angles.hpp>
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#include <mbgl/math/clamp.hpp>
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#include <numbers>
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namespace mbgl {
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class ProjectedMeters {
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private:
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double _northing; // Distance measured northwards.
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double _easting; // Distance measured eastwards.
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public:
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ProjectedMeters(double n_ = 0, double e_ = 0)
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: _northing(n_),
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_easting(e_) {
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if (std::isnan(_northing)) {
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throw std::domain_error("northing must not be NaN");
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}
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if (std::isnan(_easting)) {
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throw std::domain_error("easting must not be NaN");
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}
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}
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double northing() const { return _northing; }
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double easting() const { return _easting; }
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friend bool operator==(const ProjectedMeters& a, const ProjectedMeters& b) {
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return a._northing == b._northing && a._easting == b._easting;
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}
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friend bool operator!=(const ProjectedMeters& a, const ProjectedMeters& b) { return !(a == b); }
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};
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/// Spherical Mercator projection
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/// https://github.com/openlayers/docs/blob/c7ab69156e17bedc1059d64d7a864b7868e354c1/library/spherical_mercator.rst
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class Projection {
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public:
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// Map pixel width at given scale.
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static double worldSize(double scale) noexcept { return scale * util::tileSize_D; }
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static double getMetersPerPixelAtLatitude(double lat, double zoom) noexcept {
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const double constrainedZoom = util::clamp(zoom, util::MIN_ZOOM, util::MAX_ZOOM);
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const double constrainedScale = std::pow(2.0, constrainedZoom);
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const double constrainedLatitude = util::clamp(lat, -util::LATITUDE_MAX, util::LATITUDE_MAX);
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return std::cos(util::deg2rad(constrainedLatitude)) * util::M2PI * util::EARTH_RADIUS_M /
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worldSize(constrainedScale);
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}
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static ProjectedMeters projectedMetersForLatLng(const LatLng& latLng) noexcept {
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const double constrainedLatitude = util::clamp(latLng.latitude(), -util::LATITUDE_MAX, util::LATITUDE_MAX);
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const double constrainedLongitude = util::clamp(latLng.longitude(), -util::LONGITUDE_MAX, util::LONGITUDE_MAX);
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const double m = 1 - 1e-15;
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const double f = util::clamp(std::sin(util::deg2rad(constrainedLatitude)), -m, m);
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const double easting = util::deg2rad(util::EARTH_RADIUS_M * constrainedLongitude);
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const double northing = 0.5 * util::EARTH_RADIUS_M * std::log((1 + f) / (1 - f));
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return {northing, easting};
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}
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static LatLng latLngForProjectedMeters(const ProjectedMeters& projectedMeters) {
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double latitude = util::rad2deg(2 * std::atan(std::exp(projectedMeters.northing() / util::EARTH_RADIUS_M)) -
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(std::numbers::pi / 2.0));
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double longitude = util::rad2deg(projectedMeters.easting()) / util::EARTH_RADIUS_M;
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latitude = util::clamp(latitude, -util::LATITUDE_MAX, util::LATITUDE_MAX);
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longitude = util::clamp(longitude, -util::LONGITUDE_MAX, util::LONGITUDE_MAX);
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return {latitude, longitude};
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}
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static Point<double> project(const LatLng& latLng, double scale) noexcept {
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return project_(latLng, worldSize(scale));
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}
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/// Returns point on tile
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static Point<double> project(const LatLng& latLng, int32_t zoom) noexcept { return project_(latLng, 1 << zoom); }
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static LatLng unproject(const Point<double>& p, double scale, LatLng::WrapMode wrapMode = LatLng::Unwrapped) {
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auto p2 = p * util::DEGREES_MAX / worldSize(scale);
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return LatLng{std::atan(std::exp(util::deg2rad(util::LONGITUDE_MAX - p2.y))) * util::DEGREES_MAX / M_PI - 90.0,
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p2.x - util::LONGITUDE_MAX,
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wrapMode};
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}
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private:
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static Point<double> project_(const LatLng& latLng, double worldSize) noexcept {
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const double latitude = util::clamp(latLng.latitude(), -util::LATITUDE_MAX, util::LATITUDE_MAX);
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return Point<double>{util::LONGITUDE_MAX + latLng.longitude(),
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util::LONGITUDE_MAX -
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util::rad2deg(std::log(std::tan(M_PI / 4 + latitude * M_PI / util::DEGREES_MAX)))} *
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(worldSize / util::DEGREES_MAX);
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}
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};
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} // namespace mbgl
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