Best solution for car approaching to the gate and anpr lib

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Hi People,

I am new to OpenCV and I am working a project to detect a car. This is a little different from the ones I found online.

Check the brief description:

1. In this project the car approaches the gate then stop
2. We have a camera in front of the car capturing car image
3. Need to detect the presence of the car and take the snapshot
4. Pass the snapshot image as a parameter for my anpr library.
5. Will return the car plate and display it to the user.

I could try to run the anpr lib on every frame, but that will impact on performance. That's why I need something to detect the car first, and then pass it to my anpr lib

Thanks