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proj_transform: fix bbox reprojection

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- remove buggy calculate_bbox, use boost::geometry::envelope instead
- move helper envelope_points to anonymous namespace and make it always
  produce exactly the requested number of points, even if it's not
  evenly divisible by 4
This commit is contained in:
Mickey Rose 2018-07-10 10:37:43 +02:00
parent 2a98fe0155
commit 947e424f56
1 changed files with 70 additions and 60 deletions
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130
src/proj_transform.cpp
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@ -21,13 +21,17 @@
*****************************************************************************/
// mapnik
#include <mapnik/global.hpp>
#include <mapnik/geometry/boost_adapters.hpp>
#include <mapnik/geometry/box2d.hpp>
#include <mapnik/geometry/multi_point.hpp>
#include <mapnik/projection.hpp>
#include <mapnik/proj_transform.hpp>
#include <mapnik/coord.hpp>
#include <mapnik/util/is_clockwise.hpp>
// boost
#include <boost/geometry/algorithms/envelope.hpp>
#ifdef MAPNIK_USE_PROJ4
// proj4
#include <proj_api.h>
@ -39,6 +43,56 @@
namespace mapnik {
namespace { // (local)
// Returns points in clockwise order. This allows us to do anti-meridian checks.
template <typename T>
auto envelope_points(box2d<T> const& env, std::size_t num_points)
-> geometry::multi_point<T>
{
auto width = env.width();
auto height = env.height();
geometry::multi_point<T> coords;
coords.reserve(num_points);
// top side: left >>> right
// gets extra point if (num_points % 4 >= 1)
for (std::size_t i = 0, n = (num_points + 3) / 4; i < n; ++i)
{
auto x = env.minx() + (i * width) / n;
coords.emplace_back(x, env.maxy());
}
// right side: top >>> bottom
// gets extra point if (num_points % 4 >= 3)
for (std::size_t i = 0, n = (num_points + 1) / 4; i < n; ++i)
{
auto y = env.maxy() - (i * height) / n;
coords.emplace_back(env.maxx(), y);
}
// bottom side: right >>> left
// gets extra point if (num_points % 4 >= 2)
for (std::size_t i = 0, n = (num_points + 2) / 4; i < n; ++i)
{
auto x = env.maxx() - (i * width) / n;
coords.emplace_back(x, env.miny());
}
// left side: bottom >>> top
// never gets extra point
for (std::size_t i = 0, n = (num_points + 0) / 4; i < n; ++i)
{
auto y = env.miny() + (i * height) / n;
coords.emplace_back(env.minx(), y);
}
return coords;
}
} // namespace mapnik::(local)
proj_transform::proj_transform(projection const& source,
projection const& dest)
: source_(source),
@ -334,49 +388,6 @@ bool proj_transform::backward (box2d<double> & box) const
return true;
}
// Returns points in clockwise order. This allows us to do anti-meridian checks.
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>(std::ceil((points - 4) / 4.0));
}
steps += 1;
double xstep = width / steps;
double ystep = height / steps;
coords.resize(points);
for (int i=0; i<steps; i++) {
// top: left>right
coords[i] = coord<double, 2>(env.minx() + i * xstep, env.maxy());
// right: top>bottom
coords[i + steps] = coord<double, 2>(env.maxx(), env.maxy() - i * ystep);
// bottom: right>left
coords[i + steps * 2] = coord<double, 2>(env.maxx() - i * xstep, env.miny());
// left: bottom>top
coords[i + steps * 3] = coord<double, 2>(env.minx(), 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.
@ -393,18 +404,18 @@ bool proj_transform::backward(box2d<double>& env, int points) const
return backward(env);
}
std::vector<coord<double,2> > coords;
envelope_points(coords, env, points); // this is always clockwise
auto coords = envelope_points(env, points); // this is always clockwise
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)) {
for (auto & p : coords)
{
double z = 0;
if (!backward(p.x, p.y, z))
return false;
}
}
box2d<double> result = calculate_bbox(coords);
box2d<double> result;
boost::geometry::envelope(coords, result);
if (is_source_longlat_ && !util::is_clockwise(coords))
{
// we've gone to a geographic CS, and our clockwise envelope has
@ -432,18 +443,17 @@ bool proj_transform::forward(box2d<double>& env, int points) const
return forward(env);
}
std::vector<coord<double,2> > coords;
envelope_points(coords, env, points); // this is always clockwise
auto coords = envelope_points(env, points); // this is always clockwise
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)) {
for (auto & p : coords)
{
double z = 0;
if (!forward(p.x, p.y, z))
return false;
}
}
box2d<double> result = calculate_bbox(coords);
box2d<double> result;
boost::geometry::envelope(coords, result);
if (is_dest_longlat_ && !util::is_clockwise(coords))
{