Video Car¶

This program will provide a First Person View from the PiCar-X! Use the keyboards WSAD keys to control the direction of movement, and the O and P to adjust the speed.

Run the Code

cd /home/pi/picar-x/example
sudo python3 video_car.py

code

import sys
sys.path.append(r'/home/pi/picar-x/lib')

from utils import reset_mcu
reset_mcu()
from picarx import Picarx
from utils import run_command
import datetime

import cv2
from picamera.array import PiRGBArray
from picamera import PiCamera
import numpy as np

camera = PiCamera()
camera.resolution = (640,480)
camera.framerate = 24
camera.image_effect = "none"  #"none","negative","solarize","emboss","posterise","cartoon",
rawCapture = PiRGBArray(camera, size=camera.resolution)

power_val = 0
px = Picarx()

try:
    while True:
        for frame in camera.capture_continuous(rawCapture, format="bgr",use_video_port=True):# use_video_port=True
            img = frame.array
            cv2.imshow("video", img)

            k = cv2.waitKey(1) & 0xFF
            if k == 27:
                camera.close()
                continue
            elif k == ord('o'):
                if power_val <=90:
                    power_val += 10
                    print("power_val:",power_val)
            elif k == ord('p'):
                if power_val >=10:
                    power_val -= 10
                    print("power_val:",power_val)
            elif k == ord('w'):
                # print("w:",)
                px.set_dir_servo_angle(0)
                px.forward(power_val)
            elif k == ord('a'):
                px.set_dir_servo_angle(-30)
                px.forward(power_val)
            elif k == ord('s'):
                px.set_dir_servo_angle(0)
                px.backward(power_val)
            elif k == ord('d'):
                px.set_dir_servo_angle(30)
                px.forward(power_val)
            elif k == ord('f'):
                px.stop()

            elif k == ord('t'):
                camera.close()
                break
            rawCapture.truncate(0)

        print("take a photo wait...")
        picture_time = datetime.datetime.now().strftime('%Y-%m-%d_%H-%M-%S')
        picture_path = '/home/pi/Pictures/' + picture_time + '.jpg'

        a_t = "sudo raspistill -t 250  -w 2592 -h 1944 " + " -o " + picture_path

        print(a_t)
        run_command(a_t)

        # Vilib.shuttle_button()
        camera = PiCamera()
        camera.resolution = (640,480)
        camera.framerate = 24
        camera.image_effect = "none"  #"none","negative","solarize","emboss","posterise","cartoon",
        rawCapture = PiRGBArray(camera, size=camera.resolution)
finally:
    px.stop()
    camera.close()

How it works?

Most of this code is described in Computer Vision and Let PiCar-X Move, with the addition of the OpenCV waitKey() function.

k = cv2.waitKey(1) & 0xFF

The waitKey() is a function that waits for key-press events, and is also the only method to obtain and process events in HighGUI. This function will only work if at least one HighGUI window has been created and is active.

print("take a photo wait...")
picture_time = datetime.datetime.now().strftime('%Y-%m-%d_%H-%M-%S')
picture_path = '/home/pi/Pictures/' + picture_time + '.jpg'

a_t = "sudo raspistill -t 250  -w 2592 -h 1944 " + " -o " + picture_path

print(a_t)
run_command(a_t)

The purpose of these lines of code is to capture still photos using the Raspberry Pi camera module.

These codes are external to the main loop, and they are executed when OpenCV receives a T key on the keyboard, which breaks the main loop.

raspistill