在Cmakelist中添加opencv遇到的问题

问题

编译一个开源项目，该项目的Cmakelist：

find_package(OpenCV QUIET COMPONENTS core highgui imgproc imgcodecs)
if(NOT OpenCV_FOUND)
    find_package(OpenCV REQUIRED COMPONENTS core highgui imgproc)
endif()

cmake后出错：

CMake Error at examples/CMakeLists.txt:5 (find_package):
  By not providing "FindOpenCV.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "OpenCV", but
  CMake did not find one.

  Could not find a package configuration file provided by "OpenCV" with any
  of the following names:

    OpenCVConfig.cmake
    opencv-config.cmake

  Add the installation prefix of "OpenCV" to CMAKE_PREFIX_PATH or set
  "OpenCV_DIR" to a directory containing one of the above files.  If "OpenCV"
  provides a separate development package or SDK, be sure it has been
  installed.

最终解决方案

其实 cmakelist想做的无非是通过find_package()来添加opencv，find_package是根据系统的环境变量来找到需要的库的，出现了以上问题是我们没有设置好opencv的各种路径。这里我通过更直接的方法来添加opencv，修改cmakelist：

set(OpenCV_DIR C:/software/opencv/build)  #注意修改成自己的路径，该路径包含OpenCVConfig.cmake、opencv-config.cmake这两个文件
include_directories(${OpenCV_DIR}/include) 
add_library(opencv STATIC IMPORTED )
set_target_properties(opencv
  PROPERTIES IMPORTED_LOCATION
  ${OpenCV_DIR}/x64/vc14/lib/opencv_world330.lib) #这个路径也要设置正确

（未）解决过程

回到最初的报错信息，意思是要添加一个包含OpenCVConfig.cmake、opencv-config.cmake的路径，提示可以通过set(OpenCV_DIR)，修改cmakelist:

set(OpenCV_DIR C:/software/opencv/build)   #保证该路径下有OpenCVConfig.cmake、opencv-config.cmake文件
find_package(OpenCV QUIET COMPONENTS core highgui imgproc imgcodecs)
if(NOT OpenCV_FOUND)
    find_package(OpenCV REQUIRED COMPONENTS core highgui imgproc)
endif()

再cmake，再报错：

CMake Warning at C:/software/opencv/build/OpenCVConfig.cmake:138 (message):
  Found OpenCV Windows Pack but it has no binaries compatible with your
  configuration.

  You should manually point CMake variable OpenCV_DIR to your build of OpenCV
  library.
Call Stack (most recent call first):
  examples/CMakeLists.txt:5 (find_package)


CMake Error at examples/CMakeLists.txt:5 (find_package):
  Found package configuration file:

    C:/software/opencv/build/OpenCVConfig.cmake

  but it set OpenCV_FOUND to FALSE so package "OpenCV" is considered to be
  NOT FOUND.

前面的Warning的意思是少了路径指向Opencv的lib，提示我们手动用OpenCV_DIR 指向lib，后面的Error是说OpenCVConfig.cmake把OpenCV_FOUND设置成了False，而我们的cmakelist是需要OpenCV_FOUND为True（原因和前面是一样的，因为没有找到lib导致False）, 再次修改cmakelist：

set(OpenCV_DIR C:/software/opencv/build\  C:/software/opencv/build/x64/vc14/lib) #保证该路径下有OpenCVConfig.cmake、opencv-config.cmake文件
find_package(OpenCV QUIET COMPONENTS core highgui imgproc imgcodecs)
set(OpenCV_FOUND 1)
if(NOT OpenCV_FOUND)
    find_package(OpenCV REQUIRED COMPONENTS core highgui imgproc)
endif()

这时cmake无报错，但make会报错找不到opencv相关的头文件，把头文件路径加入cmakelist：

set(OpenCV_DIR C:/software/opencv/build\  C:/software/opencv/build/x64/vc14/lib) #保证该路径下有OpenCVConfig.cmake、opencv-config.cmake文件
find_package(OpenCV QUIET COMPONENTS core highgui imgproc imgcodecs)
set(OpenCV_FOUND 1)
if(NOT OpenCV_FOUND)
    find_package(OpenCV REQUIRED COMPONENTS core highgui imgproc)
endif()
include_directories(C:/software/opencv/build/include)    #添加头文件目录

再cmake，再make，报错：

LINK: command "C:\PROGRA~2\MICROS~1\2017\COMMUN~1\VC\Tools\MSVC\1411~1.255\bin\HostX64\x64\link.exe /nologo @CMakeFiles\squeezenet.dir\objects1.rsp /out:squeezenet.exe /implib:squeezenet.lib /pdb:E:\ncnn-master\build-vs2017\examples\squeezenet.pdb /version:0.0 /machine:x64 /INCREMENTAL:NO /subsystem:console ..\src\ncnn.lib opencv.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:squeezenet.exe.manifest" failed (exit code 1181) with the following output:
LINK : fatal error LNK1181: 无法打开输入文件“opencv.lib”
NMAKE : fatal error U1077: “E:\pcw\cmake-3.10.0-rc1-win64-x64\bin\cmake.exe”: 返回代码“0xffffffff”
Stop.
NMAKE : fatal error U1077: “"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.11.25503\bin\HostX64\x64\nmake.exe"”: 返回代码“0x2”
Stop.
NMAKE : fatal error U1077: “"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.11.25503\bin\HostX64\x64\nmake.exe"”: 返回代码“0x2”
Stop.

提示“无法打开opencv.lib”，我猜是因为添加的库名字的opencv，所以编译时会试图打开opencv.lib文件，但其实opencv在/x64/vc14/lib路径下的lib名字是opencv_worldxxx.lib，就是说我并没有正确地设置好lib的路径，因此问题仍未解决。
最终考虑到无非是一个添加链接库的问题，我就使用了前面所说的方法解决，希望大家能帮我指出后面这种方法的问题所在！