C/C++ cross-platform library

We have existing python code that interprets a person’s head movement through the camera of a device. This code is in a python library format and a runnable app on Mac osx. We have source code for both the app and the library. We need this converted into a C or a C++ library that can work on any platform. We would need to select between executing this project on C or C++ depending on which can meet our requirements. We essentially need this new library to work with Android, Samsung Tizen, LG webOS and other platforms such as iPhone iOS and Windows. Developers should be able to import our library into their respective projects and develop apps using it. Developers using Java, Python, Objective-C, C#, JavaScript and C++ should be able to use our C/C++ library. So it needs to work cross-platform and be seamless for other developers. We need an expert with C/C++ that can help us execute this project. We can specify the details of the project once we chat. We can then agree on the deliverables and the specific milestones for this project.