D:\opencv-3.4.1\opencv-3.4.1\3rdparty\protobuf\src\google\protobuf\stubs\io_win32.cc:94:3: warning: identifier 'nullptr' is a keyword in C++11 [-Wc++0x-compat]
   return s == nullptr || *s == 0;
   ^
D:\opencv-3.4.1\opencv-3.4.1\3rdparty\protobuf\src\google\protobuf\stubs\io_win32.cc: In function 'bool google::protobuf::internal::win32::{anonymous}::null_or_empty(const char_type*)':
D:\opencv-3.4.1\opencv-3.4.1\3rdparty\protobuf\src\google\protobuf\stubs\io_win32.cc:94:15: error: 'nullptr' was not declared in this scope
   return s == nullptr || *s == 0;
               ^
3rdparty\protobuf\CMakeFiles\libprotobuf.dir\build.make:412: recipe for target '3rdparty/protobuf/CMakeFiles/libprotobuf.dir/src/google/protobuf/stubs/io_win32.cc.obj' failed
mingw32-make[2]: *** [3rdparty/protobuf/CMakeFiles/libprotobuf.dir/src/google/protobuf/stubs/io_win32.cc.obj] Error 1
CMakeFiles\Makefile2:710: recipe for target '3rdparty/protobuf/CMakeFiles/libprotobuf.dir/all' failed
mingw32-make[1]: *** [3rdparty/protobuf/CMakeFiles/libprotobuf.dir/all] Error 2
Makefile:161: recipe for target 'all' failed
mingw32-make: *** [all] Error 2
 

解決方案：

在 cmake-gui 編譯配置中：

勾選 ENABLE_CXX11

然後重新Configure-Generate-mingw32-make

Makefile:161: recipe for target 'all' failed
mingw32-make: *** [all] Error 2

解決方案：

修改E:\OpenCV_3.3.1\opencv\sources\modules\videoio\src\cap_dshow.cpp檔案，在#include "DShow.h"這行的上面加一行#define NO_DSHOW_STRSAFE

然後重新Configure

D:\SoftwareRoot\opencv\sources\3rdparty\protobuf\src\google\protobuf\stubs\io_win32.cc: In function 'FILE* google::protobuf::internal::win32::fopen(const char*, const char*)':
D:\SoftwareRoot\opencv\sources\3rdparty\protobuf\src\google\protobuf\stubs\io_win32.cc:330:10: error: '::_wfopen' has not been declared
   return ::_wfopen(wpath.c_str(), wmode.c_str());
          ^
3rdparty\protobuf\CMakeFiles\libprotobuf.dir\build.make:258: recipe for target '3rdparty/protobuf/CMakeFiles/libprotobuf.dir/src/google/protobuf/stubs/io_win32.cc.obj' failed
mingw32-make[2]: *** [3rdparty/protobuf/CMakeFiles/libprotobuf.dir/src/google/protobuf/stubs/io_win32.cc.obj] Error 1
CMakeFiles\Makefile2:687: recipe for target '3rdparty/protobuf/CMakeFiles/libprotobuf.dir/all' failed
mingw32-make[1]: *** [3rdparty/protobuf/CMakeFiles/libprotobuf.dir/all] Error 2
Makefile:161: recipe for target 'all' failed
mingw32-make: *** [all] Error 2
 

解決方案：

修改D:\SoftwareRoot\opencv\MinGW_OpenCV中的CMakeCache.txt，查詢CMAKE_CXX_FLAGS，然後把CMAKE_CXX_FLAGS:STRING的值修改為-U__STRICT_ANSI__，如CMAKE_CXX_FLAGS:STRING=-U__STRICT_ANSI__

注意一定不要重新Configure-Generate！！ 做了這步操作之後CMakeCache.txt又會重新生成。直接mingw32-make

這裡的MinGW_OpenCV是CMake生成的資料夾。

還好只遇到了三個問題……什麼都不懂裝了好幾天Orz。

我的OpenCV版本是3.4.1

=====================使用QT時pro檔案需要新增的程式碼================

INCLUDEPATH += D:/SoftwareRoot/opencv/release/include \
               D:/SoftwareRoot/opencv/release/include/opencv \
               D:/SoftwareRoot/opencv/release/include/opencv2

LIBS += D:/SoftwareRoot/opencv/release/install/x86/mingw/lib/libopencv_*