qt学习之旅--MinGW32编译opencv3.0.0

1、配置环境

Qt5.6.3+mingw49_32+cmake3.24.0+opencv3.0.0

cmake下载：Download | CMake 

opencv下载：Releases - OpenCV ，往后翻历史版本，我下载的是sources

2、参考博客

博客一：Qt配置OpenCV教程，亲测已试过（详细版）_Wi~的博客-CSDN博客_qt配置opencv
博客二：Qt5.6.1+mingw32+opencv3.0使用成功_fang_chuan的博客-CSDN博客
博客三：利用CMake生成OpenCV-3.0.0的VS2013工程(解决方案),并在VS2013下进行编译的详细过程记录(从失败到成功的曲折过程)_昊虹图像算法的博客-CSDN博客_opencv3.0 源码

3、踩坑过程

3.1、opencv版本过高，QT自带的MinGW编译不过报错

开始时按照博客一的叙述，下载了cmake最新版：3.24.0，下载了opencv最新版：4.6.0。（QT是以前就下载好的版本，且选择的是mingw32位的）

一直参照博客一的操作，到进入Windows Powershell，执行 mingw32-make，却出现报错：
 error: temporary of non-literal type 'google::protobuf::internal::CallOnceInitializedMutex<std::mutex>' in a constant expression
   constexpr WrappedMutex() {}

参考别的博主回答：

所以便放弃了opencv4.6.0，后参考博客二，下载了旧版本3.0.0。

3.2、须注释add_extra_compiler_option(-Werror=non-virtual-dtor)

参考博客一、二，步骤基本差不多，值得注意的是，一定要：
①、不能勾选WITH_IPP，勾选WITH_OPENGL和WITH_QT
②、到 X:\XXXX\opencv\sources\cmake 下找到 OpenCVCompilerOptions.cmake文件，找到这句话 add_extra_compiler_option(-Werror=non-virtual-dtor) 注释掉他，不然会出现报错：error: base class 'struct IUnknown' has accessible non-virtual destructor [-Werror=non-virtual-dtor]        

3.3、下载文件 ippicv_windows_20141027.zip

当我换成opencv3.0.0后，cmake-gui.exe点击第二次configure时，整个过程花费时间不少，时间主要是耗费在了下载文件 ippicv_windows_20141027.zip上，如下图所示：
最终还是没有下载成功，见下面的报错说明。

ICV: Downloading ippicv_windows_20141027.zip...
CMake Error at 3rdparty/ippicv/downloader.cmake:71 (file):
  file DOWNLOAD HASH mismatch

    for file: [F:/Build-openCV3.0.0/opencv-3.0.0/3rdparty/ippicv/downloads/windows-b59f865d1ba16e8c84124e19d78eec57/ippicv_windows_20141027.zip]
      expected hash: [b59f865d1ba16e8c84124e19d78eec57]
        actual hash: [827569eea3481e6da39d28713cc4309d]
             status: [28;"Timeout was reached"]

Call Stack (most recent call first):
  3rdparty/ippicv/downloader.cmake:108 (_icv_downloader)
  cmake/OpenCVFindIPP.cmake:235 (include)
  cmake/OpenCVFindLibsPerf.cmake:12 (include)
  CMakeLists.txt:526 (include)


CMake Error at 3rdparty/ippicv/downloader.cmake:75 (message):
  ICV: Failed to download ICV package: ippicv_windows_20141027.zip.
  Status=28;"Timeout was reached"
Call Stack (most recent call first):
  3rdparty/ippicv/downloader.cmake:108 (_icv_downloader)
  cmake/OpenCVFindIPP.cmake:235 (include)
  cmake/OpenCVFindLibsPerf.cmake:12 (include)
  CMakeLists.txt:526 (include)

 上面的报错是说文件 ippicv_windows_20141027.zip下载失败。所以我们得重新手动下载后，将ippicv_windows_20141027.zip 放于文件夹X:/XXX/opencv-3.0.0/3rdparty/ippicv/downloads/windows-b59f865d1ba16e8c84124e19d78eec57/下(不要解压)：
该错误参考博客三改正完成

3.3.1、百度网盘资源： ippicv_windows_20141027.zip

链接：https://pan.baidu.com/s/1pz_pufD0CFUxLN3cpqpwLw?pwd=jng7 
提取码：jng7