Add grid subdivision / rasterization algorithms

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
         - cxx_compiler: g++
           c_compiler: gcc
           build_type: Coverage
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: g++
           cmake: 3.15.*
@@ -51,7 +51,7 @@ jobs:
         - cxx_compiler: g++-7
           c_compiler: gcc-7
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'g++-7-multilib gcc-7-multilib'
           cmake: 3.17.*
@@ -60,7 +60,7 @@ jobs:
         - cxx_compiler: g++-7
           c_compiler: gcc-7
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 32
           packages: 'g++-7-multilib gcc-7-multilib g++-multilib gcc-multilib'
           cmake: 3.18.*
@@ -69,7 +69,7 @@ jobs:
         - cxx_compiler: g++-8
           c_compiler: gcc-8
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'g++-8-multilib gcc-8-multilib'
           cmake: 3.21.*
@@ -78,7 +78,7 @@ jobs:
         - cxx_compiler: g++-9
           c_compiler: gcc-9
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'g++-9-multilib gcc-9-multilib'
           cmake: 3.23.*
@@ -87,7 +87,7 @@ jobs:
         - cxx_compiler: g++-10
           c_compiler: gcc-10
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'g++-10-multilib gcc-10-multilib'
           cmake: 3.25.*
@@ -129,7 +129,7 @@ jobs:
         - cxx_compiler: clang++-7
           c_compiler: clang-7
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'clang-7'
           cmake: 3.15.*
@@ -138,7 +138,7 @@ jobs:
         - cxx_compiler: clang++-8
           c_compiler: clang-8
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'clang-8'
           cmake: 3.17.*
@@ -147,7 +147,7 @@ jobs:
         - cxx_compiler: clang++-9
           c_compiler: clang-9
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'clang-9'
           cmake: 3.20.*
@@ -156,7 +156,7 @@ jobs:
         - cxx_compiler: clang++-10
           c_compiler: clang-10
           build_type: Release
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'clang-10'
           cmake: 3.21.*
@@ -168,7 +168,7 @@ jobs:
         - cxx_compiler: clang++-11
           c_compiler: clang-11
           build_type: Debug
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'clang-11'
           cmake: 3.23.*
@@ -177,7 +177,7 @@ jobs:
         - cxx_compiler: clang++-12
           c_compiler: clang-12
           build_type: ASAN
-          cxxstd: 14
+          cxxstd: 17
           arch: 64
           packages: 'clang-12'
           cmake: 3.25.*
@@ -392,7 +392,7 @@ jobs:
       matrix:
         ci:
         - os: windows-2019
-          cxxstd: 14
+          cxxstd: 17
           arch: x86
 
         - os: windows-2022

benchmarks/operation/CMakeLists.txt

@@ -27,4 +27,12 @@ if (benchmark_FOUND)
             $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/benchmarks>)
     target_link_libraries(perf_coverage_union PRIVATE
             benchmark::benchmark geos geos_cxx_flags)
+
+    add_executable(perf_grid_intersection GridIntersectionPerfTest.cpp)
+    target_include_directories(perf_grid_intersection PUBLIC
+            $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+            $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/include>
+            $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/benchmarks>)
+    target_link_libraries(perf_grid_intersection
+            benchmark::benchmark geos geos_cxx_flags)
 endif()

benchmarks/operation/GridIntersectionPerfTest.cpp

@@ -0,0 +1,121 @@
+/**********************************************************************
+ *
+ * GEOS - Geometry Engine Open Source
+ * http://geos.osgeo.org
+ *
+ * Copyright (C) 2025 ISciences LLC
+ *
+ * This is free software; you can redistribute and/or modify it under
+ * the terms of the GNU Lesser General Public Licence as published
+ * by the Free Software Foundation.
+ * See the COPYING file for more information.
+ *
+ **********************************************************************/
+
+#include <benchmark/benchmark.h>
+#include <BenchmarkUtils.h>
+
+#include <geos/geom/Envelope.h>
+#include <geos/geom/prep/PreparedGeometryFactory.h>
+#include <geos/operation/grid/Grid.h>
+
+#include <geos/operation/grid/GridIntersection.h>
+#include <geos/operation/intersection/Rectangle.h>
+#include <geos/operation/intersection/RectangleIntersection.h>
+
+using geos::geom::CoordinateXY;
+using geos::geom::Envelope;
+using geos::geom::Geometry;
+using Grid = geos::operation::grid::Grid<geos::operation::grid::bounded_extent>;
+
+template<bool AreaOnly>
+struct GridIntersection {
+    static double Intersection(const Envelope& env, int nx, int ny, const Geometry& g) {
+         Grid grid(env, env.getWidth() / nx, env.getHeight() / ny);
+         if constexpr (AreaOnly) {
+             auto result = geos::operation::grid::GridIntersection::grid_intersection(grid, g);
+             float area = 0;
+             for (std::size_t i = 0; i < result->rows(); i++) {
+                 for (std::size_t j = 0; j < result->cols(); j++) {
+                    area += (*result)(i, j);
+                 }
+             }
+            return static_cast<double>(area);
+         } else {
+             auto subdivided = geos::operation::grid::GridIntersection::subdivide_polygon(grid, g, true);
+             return subdivided->getArea();
+         }
+    }
+};
+
+using GridIntersectionAreaOnly = GridIntersection<true>;
+using GridIntersectionFull = GridIntersection<false>;
+
+template<bool UseRectangleIntersection>
+struct SingleIntersection {
+
+    static double Intersection(const Envelope& env, int nx, int ny, const Geometry& g) {
+        double dx = env.getWidth() / nx;
+        double dy = env.getHeight() / ny;
+
+        double x0 = env.getMinX();
+        double y0 = env.getMinY();
+
+        const auto& gfact = *g.getFactory();
+        auto prepGeom = geos::geom::prep::PreparedGeometryFactory::prepare(&g);
+
+        double area = 0;
+
+        for (int i = 0; i < nx; i++) {
+            for (int j = 0; j < ny; j++) {
+                Envelope subEnv(x0 + i*dx, x0 + (i+1)*dx, y0 + j*dy, y0 + (j+1)*dy);
+                auto cellGeom = gfact.toGeometry(&subEnv);
+                if (!prepGeom->intersects(cellGeom.get())) {
+                    continue;
+                }
+
+                std::unique_ptr<Geometry> isect;
+                if constexpr (UseRectangleIntersection) {
+                    geos::operation::intersection::Rectangle rect(x0 + i*dx, y0 + j*dy, x0 + (i+1)*dx, y0 + (j+1)*dy);
+                    isect = geos::operation::intersection::RectangleIntersection::clip(g, rect);
+                } else {
+                    isect = g.intersection(cellGeom.get());
+                }
+
+                area += isect->getArea();
+            }
+        }
+
+        return area;
+    }
+};
+
+using PolygonIntersection = SingleIntersection<false>;
+using RectangleIntersection = SingleIntersection<true>;
+
+template<typename Impl>
+static void BM_GridIntersection(benchmark::State& state)
+{
+    auto nCells = state.range(0);
+
+    auto nx = static_cast<int>(std::ceil(std::sqrt(nCells)));
+    auto ny = static_cast<int>(std::ceil(std::sqrt(nCells)));
+
+    CoordinateXY center;
+    Envelope env(0, nx, 0, ny);
+    env.centre(center);
+
+    auto geom = geos::benchmark::createSineStar(center, env.getWidth() / 2, 500);
+
+    for (auto _ : state) {
+        Impl::Intersection(env, nx, ny, *geom);
+    }
+
+}
+
+BENCHMARK_TEMPLATE(BM_GridIntersection, GridIntersectionAreaOnly)->Range(1000, 1000000);
+BENCHMARK_TEMPLATE(BM_GridIntersection, GridIntersectionFull)->Range(1000, 1000000);
+BENCHMARK_TEMPLATE(BM_GridIntersection, RectangleIntersection)->Range(1000, 1000000);
+BENCHMARK_TEMPLATE(BM_GridIntersection, PolygonIntersection)->Range(1000, 1000000);
+
+BENCHMARK_MAIN();

capi/geos_c.cpp

@@ -713,6 +713,19 @@ extern "C" {
         return GEOSClipByRect_r(handle, g, xmin, ymin, xmax, ymax);
     }
 
+    Geometry*
+    GEOSSubdivideByGrid(const Geometry* g, double xmin, double ymin, double xmax, double ymax,
+                        unsigned nx, unsigned ny, int include_exterior)
+    {
+        return GEOSSubdivideByGrid_r(handle, g, xmin, ymin, xmax, ymax, nx, ny, include_exterior);
+    }
+
+    int
+    GEOSGridIntersectionFractions(const Geometry* g, double xmin, double ymin, double xmax, double ymax,
+                                  unsigned nx, unsigned ny, float* buf)
+    {
+        return GEOSGridIntersectionFractions_r(handle, g, xmin, ymin, xmax, ymax, nx, ny, buf);
+    }
 
     Geometry*
     GEOSGeom_transformXY(const GEOSGeometry* g, GEOSTransformXYCallback callback, void* userdata) {

capi/geos_c.h.in

@@ -1035,6 +1035,24 @@ extern GEOSGeometry GEOS_DLL *GEOSClipByRect_r(
     double xmin, double ymin,
     double xmax, double ymax);
 
+/** \see GEOSSubdivideByGrid */
+extern GEOSGeometry GEOS_DLL *GEOSSubdivideByGrid_r(
+    GEOSContextHandle_t handle,
+    const GEOSGeometry* g,
+    double xmin, double ymin,
+    double xmax, double ymax,
+    unsigned nx, unsigned ny,
+    int include_exterior);
+
+/** \see GEOSGridIntersectionFractions */
+extern int GEOS_DLL GEOSGridIntersectionFractions_r(
+    GEOSContextHandle_t handle,
+    const GEOSGeometry* g,
+    double xmin, double ymin,
+    double xmax, double ymax,
+    unsigned nx, unsigned ny,
+    float* buf);
+
 /** \see GEOSPolygonize */
 extern GEOSGeometry GEOS_DLL *GEOSPolygonize_r(
     GEOSContextHandle_t handle,
@@ -3788,6 +3806,56 @@ extern GEOSGeometry GEOS_DLL *GEOSClipByRect(
     double xmin, double ymin,
     double xmax, double ymax);
 
+/**
+* Compute the intersection of a geometry with each polygon in
+* a rectangular grid.
+* \param g The input geometry to be clipped
+* \param xmin Left bound of grd
+* \param ymin Lower bound of grid
+* \param xmax Right bound of grid
+* \param ymax Upper bound of grid
+* \param nx number of columns in grid
+* \param ny number of rows in grid
+* \param include_exterior whether to include portions of the
+         input geometry that do not intersect the grid in
+         the returned result.
+* \return A geometry collection whose components represent the
+*         intersection with each cell in the grid.
+* Caller is responsible for freeing with GEOSGeom_destroy().
+* \see GEOSGetGridIntersectionFractions
+*
+* \since 3.14.0
+*/
+extern GEOSGeometry GEOS_DLL *GEOSSubdivideByGrid(
+    const GEOSGeometry* g,
+    double xmin, double ymin,
+    double xmax, double ymax,
+    unsigned nx, unsigned ny,
+    int include_exterior);
+
+/**
+* Determine the fraction of each cell in a rectangular grid
+* that is covered by a polygon.
+* \param g The input geometry
+* \param xmin Left bound of grd
+* \param ymin Lower bound of grid
+* \param xmax Right bound of grid
+* \param ymax Upper bound of grid
+* \param nx number of columns in grid
+* \param ny number of rows in grid
+* \param buf a buffer of size nx*ny to which the grid cell
+*        coverage fractions will be written in row-major order
+* \return 1 if the operation was successful, 0 on exception
+*
+* \since 3.14.0
+*/
+extern int GEOS_DLL GEOSGridIntersectionFractions(
+    const GEOSGeometry* g,
+    double xmin, double ymin,
+    double xmax, double ymax,
+    unsigned nx, unsigned ny,
+    float* buf);
+
 /**
 * Find paths shared between the two given lineal geometries.
 *