如何用opencv调用摄像头后标记人脸

使用OpenCV调用摄像头并标记人脸需要以下步骤：

1. 导入必要的库和模块：

import cv2
import numpy as np
import face_recognition

2. 打开摄像头：

cap = cv2.VideoCapture(0)

3. 循环读取摄像头中的每一帧：

while True:
    ret, frame = cap.read()

4. 使用face_recognition模块检测人脸：

face_locations = face_recognition.face_locations(frame)

5. 对每个检测到的人脸进行标记：

for (top, right, bottom, left) in face_locations:
    cv2.rectangle(frame, (left, top), (right, bottom), (0, 255, 0), 2)

6. 显示标记后的图像：

cv2.imshow('Video', frame)

完整代码如下：

import cv2
import numpy as np
import face_recognition

cap = cv2.VideoCapture(0)

while True:
    ret, frame = cap.read()

    face_locations = face_recognition.face_locations(frame)

    for (top, right, bottom, left) in face_locations:
        cv2.rectangle(frame, (left, top), (right, bottom), (0, 255, 0), 2)

    cv2.imshow('Video', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

运行代码后，摄像头会自动打开，即可看到标记后的人脸图像。