This is a note on how to cross compile opencv for pretty much any ARM device(HardFP supported in this case) and deploy. Native compiling in ARM devices can be painfully slow and they seem to hang often during build(mine got stuck at 43%). So if you happen to have a desktop/laptop/server running ubuntu or similar linux distro, u can build opencv in fractionth of the time taken for native compiling without any issues. Building opencv3 with TBB and NEON and VFP support can boost opencv performance. Thanks to Adrian at pyimagesearch for pointing that out. Both my PC and target machine aka orange pi zero are running ubuntu 16.04 with python2.7 and python 3.5. Let us use the term "build machine" for your PC where you are building opencv and "target machine" for the ARM single board computer.

1.Run the following commands in both machines(I think installing these in target machine only would do) to install the necessary libraries etc.(mine worked with them,so they should be enough