libopencv_imgproc.so.3.2, needed by /opt/ros/melodic/lib/libcv_bridge.so, may conflict with libopencv_imgproc.so.3.4

This error message suggests that there may be a conflict between two versions of the OpenCV library: version 3.2 and version 3.4. Specifically, it appears that the cv_bridge library in ROS Melodic requires version 3.2 of the libopencv_imgproc library, but there is also a version 3.4 of the same library installed on your system.

To resolve this conflict, you can try one of the following approaches:

1. Update ROS Melodic to a version that is compatible with OpenCV 3.4. This may require updating other packages as well, depending on their dependencies.

2. Downgrade the OpenCV library to version 3.2. This can be done by uninstalling the existing version and installing the older version from a package repository or from source code.

3. Build a custom version of cv_bridge that is compatible with OpenCV 3.4. This approach requires some knowledge of C++ programming and the ROS build system.

It's important to note that each of these approaches may have its own set of challenges and trade-offs, so it's worth considering which one is best suited for your particular use case.