编译opencv4 basic程序时出现链接错误？

Question

我使用Pacman命令安装了OpenCV。但是我得到了上百行的链接错误。我用下面的命令编译了我的程序

gcc example.cpp -o example `pkg-config --cflags --libs opencv4`

并且链接误差的小部分如下所示。

usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkRenderingFreeType_AutoInit_Destruct()'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkInteractorStyle::StartTwoPointer()'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkInteractorStyle::EndZoom()'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkSmartPointerBase::operator=(vtkObjectBase*)'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkOStrStreamWrapper::freeze(int)'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkCamera::SetUserTransform(vtkHomogeneousTransform*)'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkCommand::UnRegister()'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkRenderer::New()'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkInteractorStyle::StartDolly()'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkRenderer::SetActiveCamera(vtkCamera*)'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkInteractorObserver::ReleaseFocus()'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkInteractorObserver::ComputeDisplayToWorld(double, double, double, double*)'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkAlgorithm::Update(vtkInformation*)'
/usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../lib/libopencv_viz.so: undefined reference to `vtkMatrix4x4::New()'

Answer 1

opencv库本身就在那里，但是libopencv_viz.so需要来自vtk库的一些符号，该库在opencv的PKGBUILD中被列为optional dependency。

你应该自己安装它(例如pacman -S [--asdeps] vtk)，或者如果你认为依赖项应该是非可选的，可以向PKGBUILD maintaintes投诉。