OpenCVTest | 基于OpenCV实现人脸检测和智能选区截图（仿扫描王APP）的功能 | Computer Vision library

As the error suggests, CMake found your OpenCV installation, but it is not compatible. What is it not compatible with? Your compiler. The OpenCV installation is built with MSVC 15 (it also includes a 14 build). You have asked CMake to use MinGW as your compiler. Libraries need to have been built with the same (well, with some leeway) compiler for everything to work.

You have two options:

• Build OpenCV yourself with MinGW, or try a third-party MinGW binary distribution of OpenCV. Web searches for "opencv mingw" turn up some possibilities.
• Use the MSVC compiler for your project. Microsoft offers some free versions of its tools. Just be sure to install the optional older toolsets so that you have access to the VC 15 tools to match OpenCV.

so, building for iOS Simulator, but linking in object file built for iOS, for architecture arm64 I guess that means you need the library built for the simulator, not for the actual target device.

It works when you try compile it, using real iPhone/iPad

When program crashes like that under Qt Creator, and you have extra libraries, the very likely reason is that the extra libraries are missing from the runtime PATH.

In this case, you need to add C:\opencv-build\bin to the PATH. There are at least 3 ways to go about it.

1. Edit the system environment, so that the relevant directory is always in the system PATH. You need to restart Qt Creator for this change to take effect. This is not the recommended way, unless you actually want these things in there also for other purposes.

2. You can edit the Build environment of the project under Qt Creator Project view. There's separate configuration for each build type, so you may need to do this to them all separately, which both good and bad. It is good, because then you can have different directory for different builds (for example debug vs relase, MSVC vs MinGW builds). It's bad because it's extra hassle and makes it easier to have something wrong.

3. You can add it to the run environment in the Qt Creator Project view. Then it will be the same for all build types.

In this case, 3 is probably the way to go.

Qt Creator annoyingly does not display any information about which DLL is missing, it just says the program crashed. This can be solved by instead string the "Qt command prompt" for the correct toolchain from Windows Start menu (search Qt and you should find it). Then go to the built .exe directory and run the .exe. You should now get an error dialog where Windows tells you which DLL it failed to find. Then you can look where that DLL is and add it to the path and try again, until the program starts. After you know the directories using this method, you can then add them to Qt Creator as explained above.

EDIT1:

The real problem is in this line

The solution is to just include_directories path till /usr/local/opencv4 and it works perfectly.

However, the best way I believe is to use the find_package function. I updated my Cmake to the following and it takes care of linking during build.