在 Cygwin 上使用 CMake 编译 OpenCV 项目，并为 Windows 安装 OpenCV

Question

Situation:

I have a Windows 7 machine with OpenCV for Windows installed on it. My OpenCV C++ projects work fine with Visual Studio 2010.

I want to run my existing OpenCV C++ projects to run on Raspberry Pi and on other Linux machines.

Trouble

As a first step, I am trying to compile my .cpp & .h files using GCC on Cygwin on my Windows Machine. For this purpose I am trying to use CMake package for Cygwin , but CMake gives error that it cannot find OpenCV package. (error is listed below).

Question:

1. Do i need to install OpenCV package for Cygwin separately for CMake to work ?
2. Is there a way to using my existing OpenCV for Win to work with CMake ?
3. What environment variables need to be set ?
   (Currently only a variable OPENCV_DIR is set to C:/opencv/build)

CMakeLists.txt

cmake_minimum_required(VERSION 2.8.4) 
PROJECT (testProj)
find_package(OpenCV REQUIRED )
set( NAME_SRC
    src/main.cpp    
    src/imgProcess.cpp    
)

set( NAME_HEADERS       
     include/imgProcess.h
)

INCLUDE_DIRECTORIES( ${CMAKE_CURRENT_SOURCE_DIR}/include )
link_directories( ${CMAKE_BINARY_DIR}/bin)
set(EXECUTABLE_OUTPUT_PATH ${CMAKE_BINARY_DIR}/bin)
add_executable( testProj ${NAME_SRC} ${NAME_HEADERS} )

target_link_libraries( test ${OpenCV_LIBS} )

cmake error

$ cmake .
-- The C compiler identification is GNU 4.9.3
-- The CXX compiler identification is GNU 4.9.3
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++.exe
-- Check for working CXX compiler: /usr/bin/c++.exe -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at CMakeLists.txt:3 (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.
-- Configuring incomplete, errors occurred!
See also "/cygdrive/c/Work/Project/cmaketest/CMakeFiles/CMakeOutput.log".

Answer 1

该变量应称为OpenCV_DIR ，它必须与find_package(OpenCV REQUIRED)中的find_package(OpenCV REQUIRED)相同。

Answer 2

As @berak, stated in the comment, I installed OpenCV Package for Cygwin using Cygwin Ports. (Without any src or requiring any build, simple install only).
Had to tweak my CMakeLists.txt a little but it compiled well.

##### CMakeLists.txt ########
cmake_minimum_required(VERSION 2.8.4) 
PROJECT (test)
find_package(OpenCV REQUIRED )

set( NAME_SRC
    src/main.cpp    
    src/mytest.cpp    
)

set( NAME_HEADERS       
    include/mytest.hpp
)

set(EXECUTABLE_OUTPUT_PATH ${CMAKE_BINARY_DIR}/bin)
add_executable( test ${NAME_SRC} ${NAME_HEADERS} )
include_directories(/usr/include /usr/include/opencv2 /usr/include/opencv ${CMAKE_CURRENT_SOURCE_DIR}/include)
link_directories(/usr/lib ${CMAKE_BINARY_DIR}/bin)
target_link_libraries(test opencv_core opencv_highgui opencv_imgproc)

(Now, I have totally different trouble of runtime error : Gtk-WARNING **: cannot open display , but its another story of not having XServer on Cygwin)

Answer 3

First take the following steps to build opencv using visual studio and cmake gui.

1. Clone into the opencv source code repo

$ git clone https://github.com/Itseez/opencv.git

2. Navigate inside the folder and checkout to the specified version

$ git checkout 3.0.0

3. Create a build directory and build opencv in there using CMake and visual studio. Note that by default opencv will build dynamic libraries unless you enable the option of building opencv static libraries.

4. Once done you should handle the environment variables. Create a variable named OpenCV_DIR and point it to the build directory of opencv. Then update your PATH variable to have new opencv dll files added. Usually they can be found in the directory opencv\\build\\bin\\Release assuming you have built opencv in Release mode

Then set up your project CMakeList.txt as follows

find_package(OpenCV  REQUIRED)  

include_directories(    
    ${OpenCV_INCLUDE_DIRS}     
)

target_link_libraries(test
    ${OpenCV_LIBS}
)

The command find_package(OpenCV REQUIRED) finds the opencv configuration files in the directory "opencv/build", aka the directory in which you have built opencv (That's why you should set the value of the variable ${OpenCV_DIR} to this directory so the command find_package can find the required files in there).

The two variables {OpenCV_INCLUDE_DIRS} and ${OpenCV_LIBS} have already been set in those configuration files. So you should be all set.