Try to make OPENCV cmake FetchContentable

cpp/CMakeLists.txt

@@ -24,9 +24,10 @@
 cmake_minimum_required(VERSION 3.22)
 project(map_closures_cpp VERSION 0.1.0 LANGUAGES CXX)
 
-find_package(OpenCV REQUIRED)
+# find_package(OpenCV REQUIRED)
 
 option(USE_SYSTEM_EIGEN3 "Use system pre-installed Eigen" ON)
+option(USE_SYSTEM_OPENCV "Use system pre-installed OpenCV" ON)
 
 set(CMAKE_BUILD_TYPE Release)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

cpp/core/CMakeLists.txt

@@ -24,5 +24,5 @@
 add_library(core STATIC)
 add_library(map_closures::core ALIAS core)
 target_sources(core PRIVATE DensityMap.cpp AlignRansac2D.cpp)
-target_link_libraries(core PUBLIC Eigen3::Eigen ${OpenCV_LIBS})
+target_link_libraries(core PUBLIC Eigen3::Eigen OpenCV4)
 set_global_target_properties(core)

cpp/pipeline/MapClosures.cpp

@@ -77,6 +77,7 @@ std::pair<std::vector<int>, cv::Mat> MapClosures::MatchAndAddLocalMap(
                                    config_.hamming_distance_threshold,
                                    srrg_hbst::SplittingStrategy::SplitEven);
 
+
     const size_t clipped_top_k =
         std::min(top_k, static_cast<unsigned int>(descriptor_matches_.size()));
     std::vector<int> ref_mapclosure_indices(clipped_top_k);

cpp/thirdparty/find_dependencies.cmake

@@ -27,4 +27,20 @@ else()
   include(${CMAKE_CURRENT_LIST_DIR}/eigen/eigen.cmake)
 endif()
 
+if(${USE_SYSTEM_OPENCV})
+  find_package(OpenCV QUIET)
+else()
+  include(${CMAKE_CURRENT_LIST_DIR}/opencv/opencv.cmake)
+endif()
+# Taken from a issue in the OpenCv project (https://github.com/opencv/opencv/issues/20548#issuecomment-1325751099)
+# for some reason OpenCV does not want to convert to a FetchContent Friendly format so we need to use this trick
+add_library(OpenCV4 INTERFACE)
+target_link_libraries(OpenCV4 INTERFACE ${OpenCV_LIBS})
+target_include_directories(OpenCV4 INTERFACE
+          ${OPENCV_CONFIG_FILE_INCLUDE_DIR}
+          ${OPENCV_MODULE_opencv_core_LOCATION}/include
+          ${OPENCV_MODULE_opencv_highgui_LOCATION}/include
+          ${OpenCV_INCLUDE_DIRS}
+          )
+
 include(${CMAKE_CURRENT_LIST_DIR}/hbst/hbst.cmake)

cpp/thirdparty/opencv/opencv.cmake

@@ -0,0 +1,34 @@
+# MIT License
+#
+# Copyright (c) 2024 Saurabh Gupta, Tiziano Guadagnino, Benedikt Mersch,
+# Ignacio Vizzo, Cyrill Stachniss.
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+# Taken from a issue in the OpenCv project (https://github.com/opencv/opencv/issues/20548#issuecomment-1325751099)
+# for some reason OpenCV does not want to convert to a FetchContent Friendly format so we need to use this trick
+include(FetchContent)
+FetchContent_Declare(
+        opencv
+        GIT_REPOSITORY https://github.com/opencv/opencv.git
+        GIT_TAG 4.x
+        GIT_SHALLOW TRUE
+        GIT_PROGRESS TRUE
+)
+FetchContent_MakeAvailable(opencv)