Maybe this post can help you, I create a cross-platform app by Qt5 and opencv3.3(open source), which could run on windows, linux, android, mac. Why no ios?Because I do not have any ios device, so I cannot test it, in theory Qt5 and opencv3.3, both of them can run on ios.
The link come with binary of android, if you have any questions, please leave me a message(ex : how to build on another platforms like windows, mac, linux), please leave me a message.
Please let me join you project if possible, I am quite familiar with c++ and know how to create cross-platform apps with Qt5 and opencv.
I suggest you port to caffe, tensorflow or torch, because the models describe by these libraries supported by the dnn module of opencv3.3.