static Feature::geometry_type convertGeometry(const GeometryTileFeature& geometryTileFeature, const CanonicalTileID& tileID) {
const double size = util::EXTENT * std::pow(2, tileID.z);
const double x0 = util::EXTENT * tileID.x;
const double y0 = util::EXTENT * tileID.y;
auto tileCoordinatesToLatLng = [&] (const Point<int16_t>& p) {
double y2 = 180 - (p.y + y0) * 360 / size;
return Point<double>(
(p.x + x0) * 360 / size - 180,
360.0 / M_PI * std::atan(std::exp(y2 * M_PI / 180)) - 90.0
);
};
GeometryCollection geometries = geometryTileFeature.getGeometries();
switch (geometryTileFeature.getType()) {
case FeatureType::Unknown: {
assert(false);
return Point<double>(NAN, NAN);
}
case FeatureType::Point: {
MultiPoint<double> multiPoint;
for (const auto& p : geometries.at(0)) {
multiPoint.push_back(tileCoordinatesToLatLng(p));
}
if (multiPoint.size() == 1) {
return multiPoint[0];
} else {
return multiPoint;
}
}
case FeatureType::LineString: {
MultiLineString<double> multiLineString;
for (const auto& g : geometries) {
LineString<double> lineString;
for (const auto& p : g) {
lineString.push_back(tileCoordinatesToLatLng(p));
}
multiLineString.push_back(std::move(lineString));
}
if (multiLineString.size() == 1) {
return multiLineString[0];
} else {
return multiLineString;
}
}
case FeatureType::Polygon: {
MultiPolygon<double> multiPolygon;
for (const auto& pg : classifyRings(geometries)) {
Polygon<double> polygon;
for (const auto& r : pg) {
LinearRing<double> linearRing;
for (const auto& p : r) {
linearRing.push_back(tileCoordinatesToLatLng(p));
}
polygon.push_back(std::move(linearRing));
}
multiPolygon.push_back(std::move(polygon));
}
if (multiPolygon.size() == 1) {
return multiPolygon[0];
} else {
return multiPolygon;
}
}
}
// Unreachable, but placate GCC.
return Point<double>();
}
