Cmake Ocv_download __full__ -

You are trying to build opencv_contrib using a main opencv source version that does not match (e.g., mixing v3.4 and v4.x).

Extra modules like xfeatures2d use this to download patented algorithms like SIFT or SURF descriptors (e.g., vgg_generated_48.i ). cmake ocv_download

If your build environment lacks internet access, you can manually "prime" the cache: You are trying to build opencv_contrib using a

Manually download the files and place them in the /.cache/ / - directory. cmake ocv_download

The Deep Learning module utilizes it to fetch Protobuf dependencies or specific model weights.

The module's CMakeLists.txt is being processed before the main OpenCV configuration has defined the function. Ensure you have correctly set the OPENCV_EXTRA_MODULES_PATH in your CMake-GUI or command line. Manual Workaround (Offline Build)