undefined reference to...

wj@wj-Inspiron-5437:~/Downloads/LBD_Descriptor/build$ cmake ..
-- Configuring done
-- Generating done
-- Build files have been written to: /home/wj/Downloads/LBD_Descriptor/build
wj@wj-Inspiron-5437:~/Downloads/LBD_Descriptor/build$ make
[ 66%] Built target LineMatchingLib
Linking CXX executable TestLineMatchingAlgorithm
CMakeFiles/TestLineMatchingAlgorithm.dir/TestLineMatchingAlgorithm.cpp.o: In function `cv::String::String(char const*)':
TestLineMatchingAlgorithm.cpp:(.text._ZN2cv6StringC2EPKc[_ZN2cv6StringC5EPKc]+0x30): undefined reference to `cv::String::allocate(unsigned long)'
CMakeFiles/TestLineMatchingAlgorithm.dir/TestLineMatchingAlgorithm.cpp.o: In function `cv::String::String(std::string const&)':
TestLineMatchingAlgorithm.cpp:(.text._ZN2cv6StringC2ERKSs[_ZN2cv6StringC5ERKSs]+0x34): undefined reference to `cv::String::allocate(unsigned long)'
CMakeFiles/TestLineMatchingAlgorithm.dir/TestLineMatchingAlgorithm.cpp.o: In function `main':
TestLineMatchingAlgorithm.cpp:(.text.startup+0xfe): undefined reference to `cv::imread(cv::String const&, int)'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x12a): undefined reference to `cv::String::deallocate()'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x21e): undefined reference to `cv::imread(cv::String const&, int)'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x24a): undefined reference to `cv::String::deallocate()'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x624): undefined reference to `cv::line(cv::_InputOutputArray const&, cv::Point_<int>, cv::Point_<int>, cv::Scalar_<double> const&, int, int, int)'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x7f3): undefined reference to `cv::line(cv::_InputOutputArray const&, cv::Point_<int>, cv::Point_<int>, cv::Scalar_<double> const&, int, int, int)'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x89d): undefined reference to `cv::imwrite(cv::String const&, cv::_InputArray const&, std::vector<int, std::allocator<int> > const&)'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x8a5): undefined reference to `cv::String::deallocate()'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x939): undefined reference to `cv::imwrite(cv::String const&, cv::_InputArray const&, std::vector<int, std::allocator<int> > const&)'
TestLineMatchingAlgorithm.cpp:(.text.startup+0x941): undefined reference to `cv::String::deallocate()'
TestLineMatchingAlgorithm.cpp:(.text.startup+0xa96): undefined reference to `cv::String::deallocate()'
TestLineMatchingAlgorithm.cpp:(.text.startup+0xac9): undefined reference to `cv::String::deallocate()'
TestLineMatchingAlgorithm.cpp:(.text.startup+0xb53): undefined reference to `cv::String::deallocate()'
TestLineMatchingAlgorithm.cpp:(.text.startup+0xb96): undefined reference to `cv::String::deallocate()'
libLineMatchingLib.so: undefined reference to `cv::error(int, cv::String const&, char const*, char const*, int)'
libLineMatchingLib.so: undefined reference to `cv::write(cv::FileStorage&, cv::String const&, cv::Mat const&)'
libLineMatchingLib.so: undefined reference to `cv::FileStorage::FileStorage(cv::String const&, int, cv::String const&)'
libLineMatchingLib.so: undefined reference to `cv::operator<<(cv::FileStorage&, cv::String const&)'
collect2: error: ld returned 1 exit status
make[2]: *** [TestLineMatchingAlgorithm] Error 1
make[1]: *** [CMakeFiles/TestLineMatchingAlgorithm.dir/all] Error 2
make: *** [all] Error 2

阅读错误之后，感觉是没有找到opencv,搜了相关问题，然后修改了CMakeList.txt，解决了此问题。

PROJECT(LILIANTESTS)
cmake_minimum_required(VERSION 2.8)
find_package( OpenCV REQUIRED ) //这两句可以连接到opencv
add_executable( camera camera.cpp )
target_link_libraries( camera ${OpenCV_LIBS} )