Generalization: Switch from using CImg to OpenCV library.

.github/actions/ubuntu-prerequisites/action.yml

@@ -16,11 +16,13 @@ runs:
     - name: Install software
       run: |
         sudo apt-get install -yq --no-install-suggests --no-install-recommends \
-          cimg-dev \
           libboost-filesystem-dev \
           libboost-system-dev \
           libbz2-dev \
           libexpat1-dev \
+          libopencv-core-dev \
+          libopencv-imgcodecs-dev \
+          libopencv-imgproc-dev \
           libpotrace-dev \
           libpq-dev \
           libproj-dev \

.github/actions/win-install/action.yml

@@ -12,11 +12,11 @@ runs:
           boost-property-tree:x64-windows \
           boost-system:x64-windows \
           bzip2:x64-windows \
-          cimg:x64-windows \
           expat:x64-windows \
           libpq:x64-windows \
           lua:x64-windows \
           nlohmann-json:x64-windows \
+          opencv:x64-windows \
           proj4:x64-windows \
           zlib:x64-windows
       shell: bash

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
 
       - name: Install prerequisites
         run: |
-          brew install lua boost postgis pandoc cimg potrace nlohmann-json
+          brew install boost lua nlohmann-json opencv pandoc postgis potrace
           pip3 install psycopg2 behave osmium
           pg_ctl -D /usr/local/var/postgres init
           pg_ctl -D /usr/local/var/postgres start

.github/workflows/test-install.yml

@@ -38,13 +38,15 @@ jobs:
           sudo apt-get purge -yq postgresql*
           sudo apt-get update -qq
           sudo apt-get install -yq --no-install-suggests --no-install-recommends \
-            cimg-dev \
             libboost-filesystem-dev \
             libboost-system-dev \
             libbz2-dev \
             libexpat1-dev \
             liblua${LUA_VERSION}-dev \
             libluajit-5.1-dev \
+            libopencv-core-dev \
+            libopencv-imgcodecs-dev \
+            libopencv-imgproc-dev \
             libpotrace-dev \
             libpq-dev \
             libproj-dev \

CMakeLists.txt

@@ -211,7 +211,7 @@ include_directories(SYSTEM ${NLOHMANN_INCLUDE_DIR})
 find_path(POTRACE_INCLUDE_DIR potracelib.h)
 find_library(POTRACE_LIBRARY NAMES potrace)
 
-find_path(CIMG_INCLUDE_DIR CImg.h)
+find_package(OpenCV OPTIONAL_COMPONENTS core imgcodecs imgproc)
 
 ############### Libraries are found now ########################
 
@@ -284,13 +284,12 @@ add_subdirectory(src)
 add_executable(osm2pgsql src/osm2pgsql.cpp)
 target_link_libraries(osm2pgsql osm2pgsql_lib ${LIBS})
 
-if (${POTRACE_LIBRARY} STREQUAL "POTRACE_LIBRARY-NOTFOUND" OR ${CIMG_INCLUDE_DIR} STREQUAL "CIMG_INCLUDE_DIR-NOTFOUND")
-    message(STATUS "Did not find cimg and/or potrace library. Not building osm2pgsql-gen.")
+if (${POTRACE_LIBRARY} STREQUAL "POTRACE_LIBRARY-NOTFOUND" OR NOT OPENCV_CORE_FOUND)
+    message(STATUS "Did not find opencv and/or potrace library. Not building osm2pgsql-gen.")
 else()
     if (WITH_LUA)
-        message(STATUS "Found cimg and potrace library. Building osm2pgsql-gen.")
+        message(STATUS "Found opencv and potrace library. Building osm2pgsql-gen.")
         set(BUILD_GEN 1)
-        include_directories(SYSTEM ${CIMG_INCLUDE_DIR})
         include_directories(SYSTEM ${POTRACE_INCLUDE_DIR})
         add_executable(osm2pgsql-gen src/gen/osm2pgsql-gen.cpp
                     src/gen/canvas.cpp
@@ -305,7 +304,7 @@ else()
                     src/gen/params.cpp
                     src/gen/raster.cpp
                     src/gen/tracer.cpp)
-        target_link_libraries(osm2pgsql-gen osm2pgsql_lib ${LIBS} ${POTRACE_LIBRARY})
+        target_link_libraries(osm2pgsql-gen osm2pgsql_lib ${LIBS} ${POTRACE_LIBRARY} ${OpenCV_LIBS})
     else()
         message(STATUS "No Lua. Not building osm2pgsql-gen.")
     endif()

README.md

@@ -50,7 +50,7 @@ Required libraries are
 * [Boost libraries](https://www.boost.org/), including geometry, system and
   filesystem
 * [nlohmann/json](https://json.nlohmann.me/)
-* [CImg](https://cimg.eu/) (Optional, for generalization only)
+* [OpenCV](https://opencv.org/) (Optional, for generalization only)
 * [potrace](https://potrace.sourceforge.net/) (Optional, for generalization only)
 * [PostgreSQL](https://www.postgresql.org/) client libraries
 * [Lua](https://www.lua.org/) (Optional, used for Lua tag transforms
@@ -83,7 +83,8 @@ On a Debian or Ubuntu system, this can be done with:
 
 ```sh
 sudo apt-get install make cmake g++ libboost-dev libboost-system-dev \
-  libboost-filesystem-dev libexpat1-dev zlib1g-dev libpotrace-dev cimg-dev \
+  libboost-filesystem-dev libexpat1-dev zlib1g-dev libpotrace-dev \
+  libopencv-core-dev libopencv-imgcodecs-dev libopencv-imgproc-dev \
   libbz2-dev libpq-dev libproj-dev lua5.3 liblua5.3-dev pandoc \
   nlohmann-json3-dev pyosmium
 ```
@@ -92,7 +93,7 @@ On a Fedora system, use
 
 ```sh
 sudo dnf install cmake make gcc-c++ boost-devel expat-devel zlib-devel \
-  potrace-devel cimg-devel json-devel python3-osmium \
+  potrace-devel opencv-devel json-devel python3-osmium \
   bzip2-devel postgresql-devel proj-devel proj-epsg lua-devel pandoc
 ```
 
@@ -101,7 +102,7 @@ dependencies with:
 
 ```sh
 sudo yum install cmake make gcc-c++ boost-devel expat-devel zlib-devel \
-  potrace-devel cimg-devel json-devel python3-osmium \
+  potrace-devel opencv-devel json-devel python3-osmium \
   bzip2-devel postgresql-devel proj-devel proj-epsg lua-devel pandoc
 ```
 

src/gen/canvas.cpp

@@ -8,48 +8,66 @@
  */
 
 #include "canvas.hpp"
+
 #include "raster.hpp"
 
-cimg_library::CImg<int> canvas_t::create_pointlist(geom::point_list_t const &pl,
-                                                   tile_t const &tile) const
+#include <opencv2/imgcodecs.hpp>
+#include <opencv2/imgproc.hpp>
+
+void canvas_t::open_close(unsigned int buffer_size)
 {
-    cimg_library::CImg<int> points{static_cast<unsigned int>(pl.size()), 2};
+    auto const kernel1 = cv::getStructuringElement(
+        cv::MORPH_RECT,
+        cv::Size(static_cast<int>(buffer_size), static_cast<int>(buffer_size)));
+    auto const kernel2 = cv::getStructuringElement(
+        cv::MORPH_RECT, cv::Size(static_cast<int>(buffer_size * 2),
+                                 static_cast<int>(buffer_size * 2)));
+
+    cv::erode(m_rast, m_rast, kernel1);
+    cv::dilate(m_rast, m_rast, kernel2);
+    cv::erode(m_rast, m_rast, kernel1);
+}
+
+void canvas_t::create_pointlist(std::vector<cv::Point> *out,
+                                geom::point_list_t const &pl,
+                                tile_t const &tile) const
+{
+    out->reserve(pl.size());
 
-    int n = 0;
     for (auto const point : pl) {
         auto const tp = tile.to_tile_coords(point, m_extent);
-        points(n, 0) = static_cast<int>(static_cast<double>(m_buffer) + tp.x());
-        points(n, 1) =
-            static_cast<int>(static_cast<double>(m_buffer + m_extent) - tp.y());
-        ++n;
+        auto const x = static_cast<double>(m_buffer) + tp.x();
+        auto const y = static_cast<double>(m_buffer + m_extent) - tp.y();
+        out->emplace_back(x, y);
     }
-
-    return points;
 }
 
 std::size_t canvas_t::draw_polygon(geom::polygon_t const &polygon,
                                    tile_t const &tile)
 {
-    if (polygon.inners().empty()) {
-        m_rast.draw_polygon(create_pointlist(polygon.outer(), tile), &White);
-        return polygon.outer().size();
-    }
-
     std::size_t num_points = polygon.outer().size();
-    m_temp.draw_polygon(create_pointlist(polygon.outer(), tile), &White);
+
+    std::vector<std::vector<cv::Point>> poly_data;
+    poly_data.resize(polygon.inners().size() + 1);
+
+    create_pointlist(poly_data.data(), polygon.outer(), tile);
+    std::size_t n = 1;
     for (auto const &inner : polygon.inners()) {
         num_points += inner.size();
-        m_temp.draw_polygon(create_pointlist(inner, tile), &Black);
+        create_pointlist(&poly_data[n], inner, tile);
+        n++;
     }
-    m_rast |= m_temp;
+    cv::fillPoly(m_rast, poly_data, cv::Scalar{255});
 
     return num_points;
 }
 
 std::size_t canvas_t::draw_linestring(geom::linestring_t const &linestring,
                                       tile_t const &tile)
 {
-    m_rast.draw_line(create_pointlist(linestring, tile), &White);
+    std::vector<cv::Point> line_data;
+    create_pointlist(&line_data, linestring, tile);
+    cv::polylines(m_rast, line_data, false, cv::Scalar{255});
     return linestring.size();
 }
 
@@ -81,13 +99,13 @@ std::size_t canvas_t::draw(geom::geometry_t const &geometry, tile_t const &tile)
 
 void canvas_t::save(std::string const &filename) const
 {
-    m_rast.save(filename.c_str());
+    cv::imwrite(filename, m_rast);
 }
 
 std::string canvas_t::to_wkb(tile_t const &tile, double margin) const
 {
     std::string wkb;
-    wkb.reserve(61 + 2 + m_rast.size());
+    wkb.reserve(61 + 2 + size() * size());
 
     // header
     wkb_raster_header header{};
@@ -106,18 +124,24 @@ std::string canvas_t::to_wkb(tile_t const &tile, double margin) const
     add_raster_band(&wkb, band);
 
     // rasterdata
-    wkb.append(reinterpret_cast<char const *>(m_rast.data()), m_rast.size());
+    wkb.append(reinterpret_cast<char const *>(begin()),
+               reinterpret_cast<char const *>(end()));
 
-    assert(wkb.size() == 61 + 2 + m_rast.size());
+    assert(wkb.size() == 61 + 2 + size() * size());
 
     return wkb;
 }
 
-void canvas_t::merge(canvas_t const &other) { m_rast |= other.m_rast; }
+void canvas_t::merge(canvas_t const &other)
+{
+    cv::bitwise_or(m_rast, other.m_rast, m_rast);
+}
 
 std::string to_hex(std::string const &in)
 {
     std::string result;
+    result.reserve(in.size() * 2);
+
     char const *const lookup_hex = "0123456789ABCDEF";
 
     for (const auto c : in) {

src/gen/canvas.hpp

@@ -13,48 +13,42 @@
 #include "geom.hpp"
 #include "tile.hpp"
 
-#define cimg_display 0 // NOLINT(cppcoreguidelines-macro-usage)
-#include "CImg.h"
+#include <opencv2/core.hpp>
 
 #include <cstddef>
 
 /**
- * This class wraps the image class from the CImg library.
+ * This class wraps the image class from the OpenCV library.
  */
 class canvas_t
 {
 public:
-    static void info() { cimg_library::cimg::info(); }
-
     /**
      * Create a new image canvas. It will be quadratic and have the width and
      * height extent + 2*buffer.
      */
     canvas_t(std::size_t extent, std::size_t buffer)
-    : m_extent(extent),
-      m_buffer(buffer), m_rast{size(), size(), 1, 1, 0}, m_temp{size(), size(),
-                                                                1, 1, 0}
-    {}
+    : m_extent(extent), m_buffer(buffer), m_rast{static_cast<int>(size()),
+                                                 static_cast<int>(size()),
+                                                 CV_8UC1, cv::Scalar::all(0)}
+    {
+    }
 
     unsigned int size() const noexcept
     {
         return static_cast<unsigned int>(m_extent + 2 * m_buffer);
     }
 
-    unsigned char const *begin() const noexcept { return m_rast.begin(); }
-    unsigned char const *end() const noexcept { return m_rast.end(); }
-
-    std::size_t draw(geom::geometry_t const &geometry, tile_t const &tile);
+    unsigned char const *begin() const noexcept { return m_rast.data; }
 
-    unsigned char operator()(int x, int y) const noexcept
+    unsigned char const *end() const noexcept
     {
-        return m_rast(x, y, 0, 0);
+        return m_rast.data + (static_cast<size_t>(size() * size()));
     }
 
-    void open_close(unsigned int buffer_size)
-    {
-        m_rast.dilate(buffer_size).erode(buffer_size * 2).dilate(buffer_size);
-    }
+    std::size_t draw(geom::geometry_t const &geometry, tile_t const &tile);
+
+    void open_close(unsigned int buffer_size);
 
     void save(std::string const &filename) const;
 
@@ -63,13 +57,11 @@ class canvas_t
     void merge(canvas_t const &other);
 
 private:
-    constexpr static unsigned char const Black = 0;
-    constexpr static unsigned char const White = 255;
-
-    using image_type = cimg_library::CImg<unsigned char>;
+    using image_type = cv::Mat;
 
-    cimg_library::CImg<int> create_pointlist(geom::point_list_t const &pl,
-                                             tile_t const &tile) const;
+    void create_pointlist(std::vector<cv::Point> *out,
+                          geom::point_list_t const &pl,
+                          tile_t const &tile) const;
 
     std::size_t draw_polygon(geom::polygon_t const &polygon,
                              tile_t const &tile);
@@ -80,7 +72,6 @@ class canvas_t
     std::size_t m_extent;
     std::size_t m_buffer;
     image_type m_rast;
-    image_type m_temp;
 }; // class canvas_t
 
 std::string to_hex(std::string const &in);

src/gen/osm2pgsql-gen.cpp

@@ -712,7 +712,6 @@ int main(int argc, char *argv[])
                 break;
             case 'V': // --version
                 log_info("osm2pgsql-gen version {}", get_osm2pgsql_version());
-                canvas_t::info();
                 return 0;
             case 201: // --log-sql
                 get_logger().enable_sql();