Should i recompile opencv to run under Qt ?

[ChrisW67]

Qt is not a C++ compiler. Your code example is pure C++ code using OpenCV with an unspecified compiler. From your comment about Visual Studio I assume your compiler is MingW GCC. The error message is from the linker I think, so perhaps you have a missing lib (-l) entry. The libs are called opencv_ml etc. on Linux. Are you sure the libs are called ml210 and not just ml or opencv_ml on Windows? I don't have a Windows version to see if they are named differently.

You seem to be listing ml210 twice and ml210d (a debug version?) also. Try removing the duplicate and debug version.

If I comment CvEM em_model the code compiles:

// CvEM em_model;
CvEMParams params;

// CvEM em_model;
CvEMParams params;

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CvEMParams doesn't result in an error, so I think that the include paths are ok. Does anyone know how to solve this problem?

If this compiles and links then em_model is unused and you have already solved the problem. However, the code you linked to uses em_model (unconditionally) and will fail to compile with this line missing. Are you sure it compiles with that line commented?

Is there a reason you didn't use the latest version (2.3.1)? This may be a bug that is already fixed.