Include OpenCV library dll's with CMake

Question

I am trying to write a C++ application using the OpenCV libraries. As per the recommendation from the OpenCV maintainers, I am using CMake to generate the Makefile. My platform is Windows 7 (64 bit). My compiler is MinGW (so I am using the 'mingw32-make' tool to build the application).

Right now I am trying to make sure my setup is correct so I can move forward with the code. I have verified that the OpenCV libraries have been built correctly. I then tried to verify that I could use CMake to include the OpenCV libraries in my build. I am using the following sample code from an OpenCV tutorial:

DisplayImage.cpp

#include <cv.h>
#include <highgui.h>

using namespace cv;

int main( int argc, char** argv )
{
    Mat image;
    image = imread( argv[1], 1 );

    if (argc != 2 || !image.data)
    {
        printf( "No image data \n" );
        return -1;
    }

    namedWindow( "Display Image", CV_WINDOW_AUTOSIZE );
    imshow( "Display Image", image );

    waitKey(0);

    return 0;
}

CMakeLists.txt

cmake_minimum_required( VERSION 2.8 )

project( DisplayImage )
find_package( OpenCV REQUIRED )
add_executable( DisplayImage DisplayImage )
target_link_libraries( DisplayImage ${OpenCV_LIBS} )

I used cmake-gui to generate the Makefile, then used mingw32-make to build the application. Everything works fine and the program compiles with no errors. However, when I try to run it, Windows stops and complains that it needs libopencv_core231.dll. I have checked and this dll is in my (OpenCV Build location)/bin directory. How can I get CMake/MinGW to include this when compiling?

Answer 1

copy opencv dlls into your executable folder.

MACRO (COPY_DLL trgt libname)
        ADD_CUSTOM_COMMAND (
        TARGET ${trgt}
        POST_BUILD
        COMMAND ${CMAKE_COMMAND}
        ARGS -E copy "${OPENCVDIR/bin}/${libname}.dll" ${CMAKE_CURRENT_BINARY_DIR}
    )
ENDMACRO (COPY_DLL)

Answer 2

In my case, I looked for something working using visual Studio (which supports multiple configurations in the build tree), the command would be slightly modified. the command works in parallel of find_package( OpenCV REQUIRED )

first: get output dll (build as the unique opencv_world lib)

get_target_property(__dll_dbg opencv_world IMPORTED_LOCATION_DEBUG)
get_target_property(__dll_release opencv_world  IMPORTED_LOCATION_RELEASE)

Then you could add a command:

add_custom_command(TARGET ${TARGET_NAME} POST_BUILD        # Adds a post-build event the TARGET
    COMMAND ${CMAKE_COMMAND} -E copy_if_different           # which executes "cmake - E copy_if_different..."
    "$<$<CONFIG:debug>:${__dll_dbg}>$<$<CONFIG:release>:${__dll_release}>"      # <--this is in-file
    $<TARGET_FILE_DIR:${TARGET_NAME}>                        # <--this is out-file path
        # another dll copy if needed here
    COMMENT "    [1718_34_ATK] copy dlls realsense2 and opencv_world")

Answer 3

I use configure_file(...) which copies specified .dll files when they change (rarely) for the right compiler using ${_OpenCV_LIB_PATH}.

find_package(OpenCV REQUIRED)
configure_file("${_OpenCV_LIB_PATH}/opencv_world451d.dll" ${CMAKE_CURRENT_BINARY_DIR} COPYONLY)