写出python通过opencv调用摄像头实现米粒计数的代码

Sure, here is an example code that uses OpenCV to count rice grains in an image captured from a camera:

import cv2

cap = cv2.VideoCapture(0)  # open default camera

while True:
    ret, frame = cap.read()  # get a frame from the camera

    # apply some image processing operations to highlight rice grains
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    thresh = cv2.threshold(gray, 160, 255, cv2.THRESH_BINARY)[1]
    eroded = cv2.erode(thresh, (5,5), iterations=5)
    cnts = cv2.findContours(eroded, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
    cnts = cnts[0] if len(cnts) == 2 else cnts[1]

    # draw a bounding box around each rice grain and count them
    count = 0
    for c in cnts:
        area = cv2.contourArea(c)
        if area > 50:
            x,y,w,h = cv2.boundingRect(c)
            cv2.rectangle(frame, (x,y), (x+w,y+h), (0,255,0), 2)
            count += 1

    # show the image with rice grains and count
    cv2.putText(frame, "Count: {}".format(count), (10,30), cv2.FONT_HERSHEY_SIMPLEX, 1, (0,0,255), 2)
    cv2.imshow("Rice Grains Counter", frame)

    # exit when 'q' key is pressed
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

This code captures frames from the default camera, applies some image processing