8. Stare at You¶

This project is also based on the 7. Computer Vision project, with the addition of face detection algorithms.

When you appear in front of the camera, it will recognize your face and adjust its gimbal to keep your face in the center of the frame.

You can view the screen at http://<your IP>:9000/mjpg.

Run the Code

cd ~/picar-x/example
sudo python3 8.stare_at_you.py

When the code is run, the car’s camera will always be staring at your face.

Code

from picarx import Picarx
from time import sleep
from vilib import Vilib

px = Picarx()

def clamp_number(num,a,b):
    return max(min(num, max(a, b)), min(a, b))

def main():
    Vilib.camera_start()
    Vilib.display()
    Vilib.face_detect_switch(True)
    x_angle =0
    y_angle =0
    while True:
        if Vilib.detect_obj_parameter['human_n']!=0:
            coordinate_x = Vilib.detect_obj_parameter['human_x']
            coordinate_y = Vilib.detect_obj_parameter['human_y']

            # change the pan-tilt angle for track the object
            x_angle +=(coordinate_x*10/640)-5
            x_angle = clamp_number(x_angle,-35,35)
            px.set_cam_pan_angle(x_angle)

            y_angle -=(coordinate_y*10/480)-5
            y_angle = clamp_number(y_angle,-35,35)
            px.set_cam_tilt_angle(y_angle)

            sleep(0.05)

        else :
            pass
            sleep(0.05)

if __name__ == "__main__":
    try:
    main()

    finally:
        px.stop()
        print("stop and exit")
        sleep(0.1)

How it works?

These lines of code in while True make the camera follow the face.

while True:
    if Vilib.detect_obj_parameter['human_n']!=0:
        coordinate_x = Vilib.detect_obj_parameter['human_x']
        coordinate_y = Vilib.detect_obj_parameter['human_y']

        # change the pan-tilt angle for track the object
        x_angle +=(coordinate_x*10/640)-5
        x_angle = clamp_number(x_angle,-35,35)
        px.set_cam_pan_angle(x_angle)

        y_angle -=(coordinate_y*10/480)-5
        y_angle = clamp_number(y_angle,-35,35)
        px.set_cam_tilt_angle(y_angle)

Check if there is a detected human face

Vilib.detect_obj_parameter['human_n'] != 0

If a human face is detected, obtain the coordinates ( coordinate_x and coordinate_y ) of the detected face.
Calculate new pan and tilt angles ( x_angle and y_angle ) based on the detected face’s position and adjust them to follow the face.
Limit the pan and tilt angles within the specified range using the clamp_number function.
Set the camera’s pan and tilt angles using px.set_cam_pan_angle() and px.set_cam_tilt_angle() .