Add support for getting projected coordinates

CMakeLists.txt

@@ -53,6 +53,7 @@ endif()
 add_library(spherely MODULE
   src/geography.cpp
   src/predicates.cpp
+  src/projections.cpp
   src/spherely.cpp
   )
 

src/geography.cpp

@@ -244,7 +244,7 @@ void init_geography(py::module &m) {
     )pbdoc");
 
     pygeography.def("__repr__", [](const Geography &geog) {
-        s2geog::WKTWriter writer;
+        s2geog::WKTWriter writer(6);
         return writer.write_feature(geog.geog());
     });
 

src/projections.cpp

@@ -0,0 +1,49 @@
+#include <stdexcept>
+#include <iostream>
+
+#include <s2/s2projections.h>
+#include <s2/s2latlng.h>
+#include <s2geography.h>
+
+#include "geography.hpp"
+#include "pybind11.hpp"
+
+namespace py = pybind11;
+namespace s2geog = s2geography;
+using namespace spherely;
+
+
+std::tuple<double, double> project_mercator(py::object obj) {
+    auto geog = (static_cast<PyObjectGeography&>(obj)).as_geog_ptr();
+    if (geog->geog_type() != GeographyType::Point) {
+        throw py::value_error("test");
+    }
+    auto point = static_cast<Point*>(geog);
+    auto s2point = point->s2point();
+
+    auto projection = S2::MercatorProjection(20037508.3427892);
+    auto r2point = projection.Project(s2point);
+    double x = r2point.x();
+    double y = r2point.y();
+
+    return std::make_tuple(x, y);
+}
+
+
+void init_projections(py::module& m) {
+    // m.def("intersects", py::vectorize(&intersects), py::arg("a"), py::arg("b"),
+    //       R"pbdoc(
+    //     Returns True if A and B share any portion of space.
+
+    //     Intersects implies that overlaps, touches and within are True.
+
+    //     Parameters
+    //     ----------
+    //     a, b : :py:class:`Geography` or array_like
+    //         Geography object(s)
+
+    // )pbdoc");
+
+    m.def("project_mercator", &project_mercator);
+
+    }

src/spherely.cpp

@@ -7,6 +7,8 @@ namespace py = pybind11;
 
 void init_geography(py::module&);
 void init_predicates(py::module&);
+void init_projections(py::module&);
+
 
 PYBIND11_MODULE(spherely, m) {
     m.doc() = R"pbdoc(
@@ -19,6 +21,7 @@ PYBIND11_MODULE(spherely, m) {
 
     init_geography(m);
     init_predicates(m);
+    init_projections(m);
 
 #ifdef VERSION_INFO
     m.attr("__version__") = MACRO_STRINGIFY(VERSION_INFO);