I'm using vcpkg to install OpenCV4 on Windows. But when I try to link my application, one of the OpenCV classes I'm using is giving me trouble:
2>main.obj : error LNK2019: unresolved external symbol "public: __cdecl cv::VideoWriter::VideoWriter(void)" (??0VideoWriter@cv@@QEAA@XZ) referenced in function main
2>main.obj : error LNK2019: unresolved external symbol "public: virtual __cdecl cv::VideoWriter::~VideoWriter(void)" (??1VideoWriter@cv@@UEAA@XZ) referenced in function main
2>main.obj : error LNK2019: unresolved external symbol "public: virtual bool __cdecl cv::VideoWriter::open(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &,int,double,class cv::Size_<int>,bool)" (?open@VideoWriter@cv@@UEAA_NAEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@HNV?$Size_@H@2@_N@Z) referenced in function main
So I'm thinking I need to enable a non-default feature. OpenCV was originally installed like this:
vcpkg install --triplet x64-windows-static-md opencv4
By default, this seems to install [dnn,jpeg,opengl,png,tiff,webp].
I've also tried adding a few more of the optional features, including:
vcpkg install --triplet x64-windows-static-md opencv4[core,jpeg,opengl,png,tiff,webp,ffmpeg,openmp]
Output:
...cut...
The package opencv4:x64-windows-static-md provides CMake targets:
find_package(OpenCV CONFIG REQUIRED)
# Note: 14 target(s) were omitted.
target_link_libraries(main PRIVATE quirc opencv_ml libprotobuf opencv_core)
I'm using the vcpkg toolchain file when calling cmake to create the project. And the relevant portion of my CMakeLists.txt file contains the following as instructed by vcpkg:
FIND_PACKAGE(OpenCV CONFIG REQUIRED)
INCLUDE_DIRECTORIES ( BEFORE ${OpenCV_INCLUDE_DIRS} )
ADD_EXECUTABLE ( mytest main.cpp )
TARGET_LINK_LIBRARIES ( mytest PRIVATE quirc opencv_ml libprotobuf opencv_core )
Part of the problem is the vcpkg ports/opencv4/control file contains probably 20 optional features, and the descriptions are nearly useless.
My question:
Anyone know what vcpkg feature is needed to get access to the cv::VideoWriter class, or what to look for in the code so I can figure out which optional feature is required?
As @squareskittles commented, the solution is due to some missing names in the TARGET_LINK_LIBRARIES line generated by vcpkg.
The solution for me was to changed this line:
TARGET_LINK_LIBRARIES ( mytest PRIVATE quirc opencv_ml libprotobuf opencv_core )
...to instead look like this:
TARGET_LINK_LIBRARIES ( mytest PRIVATE quirc opencv_ml libprotobuf opencv_core opencv_videoio )
And in one of my other test apps, I also had to add opencv_highgui. Looks like the "target" lines generated by vcpkg don't contain everything needed.