I am trying to implement Microsoft Azure Cognitive Service Face Api for face recognition. Followed by https://go.microsoft.com/fwlink/?linkid=2184104 i created .NET Core console application and everything works fine. Now i would like to use this code in android app, but i am pretty stuck. Should i create rest api from existing C# code? Or there is android library that allows me to use face api directly like in console app?
Since Cognitive Services are already APIs, you could talk to the API directly and process the response right inside your Android code.
Please keep in mind that this does leave a potential security issue if the application is meant to go into the store / public. Users could look at the traffic or decompile your app, find your access keys and use your Cognitive Service for their own applications. In that case it could be interesting to wrap it in your own API and have some security checks in place there like rate limiting or call quota. Of course you need to make sure to use your access key inside of your own API to hide it from being seen externally.
Still, this leaves room for abuse. You now implemented a public API that, again, anybody could talk to. There are quite a few interesting discussions found on this, like this question right here on Stack Overflow: Restrict API requests to only my own mobile app.