I'm wondering if it's possible to recognize an object with the camera.
What library I have to use?
OpenCV is probably your best choice. It has iOS and Android versions, but they're native, so you'd need to create binding libraries for them (or find existing ones. I know other people have used OpenCV with Xamarin before.) You might also look at this, I'm not sure if it would be helpful. Maybe not.
This library also looks promising, but I've yet to use it:
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