mapnik/src/well_known_srs.cpp

/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2017 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

// mapnik
#include <mapnik/well_known_srs.hpp>
#include <mapnik/util/trim.hpp>
#include <mapnik/enumeration.hpp>

#pragma GCC diagnostic push
#include <mapnik/warning_ignore.hpp>
#include <boost/optional.hpp>
#pragma GCC diagnostic pop

// stl
#include <cmath>

namespace mapnik {

extern std::string const MAPNIK_LONGLAT_PROJ =
    "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs";

extern std::string const MAPNIK_GMERC_PROJ =
    "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0"
    " +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over";

static const char * well_known_srs_strings[] = {
    "mapnik-longlat",
    "mapnik-gmerc",
    ""
};

boost::optional<well_known_srs_e> is_well_known_srs(std::string const& srs)
{
    if (srs == "+init=epsg:4326" || srs == MAPNIK_LONGLAT_PROJ)
    {
        return boost::optional<well_known_srs_e>(mapnik::WGS_84);
    }
    else if (srs == "+init=epsg:3857" || srs == MAPNIK_GMERC_PROJ)
    {
        return boost::optional<well_known_srs_e>(mapnik::G_MERC);
    }
    return boost::optional<well_known_srs_e>();
}

boost::optional<bool> is_known_geographic(std::string const& srs)
{
    std::string trimmed = util::trim_copy(srs);
    if (trimmed == "+init=epsg:3857")
    {
        return boost::optional<bool>(false);
    }
    else if (trimmed == "+init=epsg:4326")
    {
        return boost::optional<bool>(true);
    }
    else if (srs.find("+proj=") != std::string::npos)
    {
        if ((srs.find("+proj=longlat") != std::string::npos) ||
                          (srs.find("+proj=latlong") != std::string::npos) ||
                          (srs.find("+proj=lonlat") != std::string::npos) ||
                          (srs.find("+proj=latlon") != std::string::npos)
                         )
        {
            return boost::optional<bool>(true);
        }
        else
        {
            return boost::optional<bool>(false);
        }
    }
    return boost::optional<bool>();
}

IMPLEMENT_ENUM( well_known_srs_e, well_known_srs_strings )

bool lonlat2merc(double & x, double & y)
{
    using namespace util;
    auto dx = clamp(x, -180.0, 180.0);
    auto dy = clamp(y, -MERC_MAX_LATITUDE, MERC_MAX_LATITUDE);
    x = EARTH_RADIUS * radians(dx);
    y = EARTH_RADIUS * std::log(std::tan(radians(90 + dy) / 2));
    return true;
}

bool lonlat2merc(double * x, double * y, std::size_t point_count, std::size_t stride)
{
    for (std::size_t i = 0; i < point_count; ++i)
    {
        lonlat2merc(x[i * stride], y[i * stride]);
    }
    return true;
}

bool lonlat2merc(std::vector<geometry::point<double>> & ls)
{
    for (auto & p : ls)
    {
        lonlat2merc(p.x, p.y);
    }
    return true;
}

bool merc2lonlat(double & x, double & y)
{
    using namespace util;
    auto rx = clamp(x / EARTH_RADIUS, -pi, pi);
    auto ry = clamp(y / EARTH_RADIUS, -pi, pi);
    x = degrees(rx);
    y = degrees(2 * std::atan(std::exp(ry)) - pi / 2);
    return true;
}

bool merc2lonlat(double * x, double * y, std::size_t point_count, std::size_t stride)
{
    for(std::size_t i = 0; i < point_count; ++i)
    {
        merc2lonlat(x[i * stride], y[i * stride]);
    }
    return true;
}

bool merc2lonlat(std::vector<geometry::point<double>> & ls)
{
    for (auto & p : ls)
    {
        merc2lonlat(p.x, p.y);
    }
    return true;
}

}