The subfolders include Dockerfiles for extending both i686
and x86_64
manylinux1 and manylinux2014 images.
Manylinux2014 is used in wheels with version 3.4.10.* / 4.3.0.* and above.
The extended images were created to be able to build OpenCV in reasonable time with Travis. The images are hosted at https://quay.io/user/skvark.
See the dockerfiles for more info.