Comment 2 for bug 1765282

This snapcraft.yaml is very dependent on your host system, which isn't really how snapcraft was designed to be used. It's impossible for us to know exactly what's happening as a result. You should get rid of that first part, and stage those packages directly instead, something like this:

# ...
parts:
  image-reading2:
    plugin: cmake
    source: src
    build-packages:
        - g++
    stage-packages:
        - libopencv-core3.2
        - libopencv-highgui3.2
        - libopencv-imgproc3.2
        - libopencv-imgcodecs3.2

That said, that still may not be what you want, since you probably want to ensure the -dev packages are installed as well (e.g. libopencv-highgui-dev in build-packages), but I won't assume too much.