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mapnik/src/proj_transform.cpp

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/*****************************************************************************
*
* This file is part of Mapnik (c++ mapping toolkit)
*
* Copyright (C) 2011 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/global.hpp>
#include <mapnik/proj_transform.hpp>
#include <mapnik/coord.hpp>
#include <mapnik/utils.hpp>
// proj4
#include <proj_api.h>
// stl
#include <vector>
static const float MAXEXTENT = 20037508.34;
static const float M_PI_by2 = M_PI / 2;
static const float D2R = M_PI / 180;
static const float R2D = 180 / M_PI;
static const float M_PIby360 = M_PI / 360;
static const float MAXEXTENTby180 = MAXEXTENT/180;
namespace mapnik {
proj_transform::proj_transform(projection const& source,
projection const& dest)
: source_(source),
dest_(dest)
{
is_source_longlat_ = source_.is_geographic();
is_dest_longlat_ = dest_.is_geographic();
is_source_equal_dest_ = (source_ == dest_);
if (source.params() == "+init=epsg:3857" && dest.params() == "+init=epsg:4326")
{
wgs84_to_merc_ = true;
}
else
{
wgs84_to_merc_ = false;
}
}
bool proj_transform::equal() const
{
return is_source_equal_dest_;
}
bool proj_transform::forward (double & x, double & y , double & z) const
{
return forward(&x, &y, &z, 1);
}
bool proj_transform::forward (double * x, double * y , double * z, int point_count) const
{
if (is_source_equal_dest_)
return true;
if (wgs84_to_merc_) {
int i;
for(i=0; i<point_count; i++) {
x[i] = (x[i] / MAXEXTENT) * 180;
y[i] = (y[i] / MAXEXTENT) * 180;
y[i] = R2D * (2 * atan(exp(y[i] * D2R)) - M_PI_by2);
if (x[i] > 180) x[i] = 180;
if (x[i] < -180) x[i] = -180;
if (y[i] > 85.0511) y[i] = 85.0511;
if (y[i] < -85.0511) y[i] = -85.0511;
}
return true;
}
if (is_source_longlat_)
{
int i;
for(i=0; i<point_count; i++) {
x[i] *= DEG_TO_RAD;
y[i] *= DEG_TO_RAD;
}
}
do {
#if defined(MAPNIK_THREADSAFE) && PJ_VERSION < 480
mutex::scoped_lock lock(projection::mutex_);
#endif
if (pj_transform( source_.proj_, dest_.proj_, point_count,
0, x,y,z) != 0)
{
return false;
}
} while(false);
if (is_dest_longlat_)
{
int i;
for(i=0; i<point_count; i++) {
x[i] *= RAD_TO_DEG;
y[i] *= RAD_TO_DEG;
}
}
return true;
}
bool proj_transform::backward (double * x, double * y , double * z, int point_count) const
{
if (is_source_equal_dest_)
return true;
if (wgs84_to_merc_) {
int i;
for(i=0; i<point_count; i++) {
x[i] = x[i] * MAXEXTENTby180;
y[i] = std::log(tan((90 + y[i]) * M_PIby360)) / D2R;
y[i] = y[i] * MAXEXTENTby180;
if (x[i] > MAXEXTENT) x[i] = MAXEXTENT;
if (x[i] < -MAXEXTENT) x[i] = -MAXEXTENT;
if (y[i] > MAXEXTENT) y[i] = MAXEXTENT;
if (y[i] < -MAXEXTENT) y[i] = -MAXEXTENT;
}
return true;
}
if (is_dest_longlat_)
{
int i;
for(i=0; i<point_count; i++) {
x[i] *= DEG_TO_RAD;
y[i] *= DEG_TO_RAD;
}
}
{
#if defined(MAPNIK_THREADSAFE) && PJ_VERSION < 480
mutex::scoped_lock lock(projection::mutex_);
#endif
if (pj_transform( dest_.proj_, source_.proj_, point_count,
0, x,y,z) != 0)
{
return false;
}
}
if (is_source_longlat_)
{
int i;
for(i=0; i<point_count; i++) {
x[i] *= RAD_TO_DEG;
y[i] *= RAD_TO_DEG;
}
}
return true;
}
bool proj_transform::backward (double & x, double & y , double & z) const
{
return backward(&x, &y, &z, 1);
}
bool proj_transform::forward (box2d<double> & box) const
{
if (is_source_equal_dest_)
return true;
double minx = box.minx();
double miny = box.miny();
double maxx = box.maxx();
double maxy = box.maxy();
double z = 0.0;
if (!forward(minx,miny,z))
return false;
if (!forward(maxx,maxy,z))
return false;
box.init(minx,miny,maxx,maxy);
return true;
}
bool proj_transform::backward (box2d<double> & box) const
{
if (is_source_equal_dest_)
return true;
double minx = box.minx();
double miny = box.miny();
double maxx = box.maxx();
double maxy = box.maxy();
double z = 0.0;
if (!backward(minx,miny,z))
return false;
if (!backward(maxx,maxy,z))
return false;
box.init(minx,miny,maxx,maxy);
return true;
}
void envelope_points(std::vector< coord<double,2> > & coords, box2d<double>& env, int points)
{
double width = env.width();
double height = env.height();
int steps;
if (points <= 4) {
steps = 0;
} else {
steps = static_cast<int>(ceil((points - 4) / 4.0));
}
steps += 1;
double xstep = width / steps;
double ystep = height / steps;
for (int i=0; i<=steps; i++) {
coords.push_back(coord<double,2>(env.minx() + i * xstep, env.miny()));
coords.push_back(coord<double,2>(env.minx() + i * xstep, env.maxy()));
}
for (int i=1; i<steps; i++) {
coords.push_back(coord<double,2>(env.minx(), env.miny() + i * ystep));
coords.push_back(coord<double,2>(env.maxx(), env.miny() + i * ystep));
}
}
box2d<double> calculate_bbox(std::vector<coord<double,2> > & points) {
std::vector<coord<double,2> >::iterator it = points.begin();
std::vector<coord<double,2> >::iterator it_end = points.end();
box2d<double> env(*it, *(++it));
for (; it!=it_end; ++it) {
env.expand_to_include(*it);
}
return env;
}
/* More robust, but expensive, bbox transform
* in the face of proj4 out of bounds conditions.
* Can result in 20 -> 10 r/s performance hit.
* Alternative is to provide proper clipping box
* in the target srs by setting map 'maximum-extent'
*/
bool proj_transform::backward(box2d<double>& env, int points) const
{
if (is_source_equal_dest_)
return true;
std::vector<coord<double,2> > coords;
envelope_points(coords, env, points);
double z;
for (std::vector<coord<double,2> >::iterator it = coords.begin(); it!=coords.end(); ++it) {
z = 0;
if (!backward(it->x, it->y, z)) {
return false;
}
}
box2d<double> result = calculate_bbox(coords);
env.re_center(result.center().x, result.center().y);
env.height(result.height());
env.width(result.width());
return true;
}
bool proj_transform::forward(box2d<double>& env, int points) const
{
if (is_source_equal_dest_)
return true;
std::vector<coord<double,2> > coords;
envelope_points(coords, env, points);
double z;
for (std::vector<coord<double,2> >::iterator it = coords.begin(); it!=coords.end(); ++it) {
z = 0;
if (!forward(it->x, it->y, z)) {
return false;
}
}
box2d<double> result = calculate_bbox(coords);
env.re_center(result.center().x, result.center().y);
env.height(result.height());
env.width(result.width());
return true;
}
mapnik::projection const& proj_transform::source() const
{
return source_;
}
mapnik::projection const& proj_transform::dest() const
{
return dest_;
}
}
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