# CMake errors on open example

Source: https://forum.modalai.com/topic/272/cmake-errors-on-open-example
Category: VOXL SDK and Software (https://forum.modalai.com/category/47/voxl-sdk-and-software)
Posted: 2021-06-07 17:00:01 UTC by shlee853
Replies: 3 · Views: 1052

## shlee853 · 2021-06-07 17:00:01 UTC

I'm trying to build april-tag-detect examples for opencv on VOXL.

Actually this examples is based on opencv 3.4, but, I updated version to 4.2.

https://gitlab.com/voxl-public/core-libs/voxl-opencv

It fails on build because of missing f package.
    
    yocto:~/opencv/examples/april-tag-detect$ cmake CMakeLists.txt 
    -- 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++
    -- Check for working CXX compiler: /usr/bin/c++ -- 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:4 (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 "/home/root/opencv/examples/april-tag-detect/CMakeFiles/CMakeOutput.log".
    yocto:~/opencv/examples/april-tag-detect$ 
    
Could you please let me know advice to find opencv package on VOXL?

thanks,

## Reply by Chad Sweet (ModalAI staff) · 2021-06-07 17:11:59 UTC

4.5 is hosted here
http://voxl-packages.modalai.com/stable/

## Reply by shlee853 · 2021-06-07 22:22:26 UTC (in reply to Chad Sweet)

@Chad-Sweet I'm not compiling opencv libraries.

as you know above scripts, I has some errors on building examples for opencv.

I think it can't find FindOpenCV.cmake file during compiling.

Thanks,

## Reply by Chad Sweet (ModalAI staff) · 2021-06-08 00:48:53 UTC

This cmake file has a good example of finding OpenCV libs using cmake

https://gitlab.com/voxl-public/core-libs/libmodal_exposure/-/blob/master/library/CMakeLists.txt