从网络摄像头拍摄图像

错误的根源是您使用的文件名带有冒号 :。

cv2.imwrite(filename='saved_img.jpg,%Y-%b-%d %H:%M:%S', img=frame)

包含冒号的文件名是非法的。

• 图像（框架）未写入文件。
• 读取图像img_ = cv2.imread('saved_img.jpg,%Y-%b-%d %H:%M:%S', cv2.IMREAD_ANYCOLOR)返回None。
• 传递None值cv2.cvtColor引发OpenCV异常。

建议的解决方法：

• 使用有效的文件名，例如：file_name = datetime.datetime.now().strftime('%Y-%m-%d_%H-%M- %S.jpg')
• file_name读写时使用变量。
• 我还建议以验证check是True使用前frame。

我创建了一个示例代码进行测试。
该代码生成合成视频文件，并从生成的文件而不是从摄像机读取帧。

这是测试代码：

import numpy as np
import cv2
import datetime

intput_filename = 'input_vid.avi'

# Generate synthetic video files to be used as input:
###############################################################################
width, height, n_frames = 640, 480, 100  # 100 frames, resolution 640x480

# Use motion JPEG codec (for testing)
synthetic_out = cv2.VideoWriter(intput_filename, cv2.VideoWriter_fourcc(*'MJPG'), 25, (width, height))

for i in range(n_frames):
    img = np.full((height, width, 3), 60, np.uint8)
    cv2.putText(img, str(i+1), (width//2-100*len(str(i+1)), height//2+100), cv2.FONT_HERSHEY_DUPLEX, 10, (30, 255, 30), 20)  # Green number
    synthetic_out.write(img)

synthetic_out.release()
###############################################################################


i = 1
key = cv2.waitKey(1)

# Read video from file instead of from camera (for testing)
webcam = cv2.VideoCapture(intput_filename)

while True:
    try:
        check, frame = webcam.read()
        print(check)  # prints true as long as the webcam is running

        if check:
            print(frame)  # prints matrix values of each frame
            cv2.imshow("Capturing", frame)

            if key == ord('s'):
                file_name = datetime.datetime.now().strftime('%Y-%m-%d_%H-%M-%S.jpg')

                cv2.imwrite(file_name, img=frame)
                #print('Timestamp: {:%Y-%b-%d %H:%M:%S}'.format(datetime.datetime.now()))
                i += 1
                print(str(i))

                # webcam.release()
                img_new = cv2.imread(file_name, cv2.IMREAD_GRAYSCALE)
                # cv2.imshow("Captured Image", img_new)
                # cv2.waitKey(1925)
                print("Processing image...")
                img_ = cv2.imread(file_name, cv2.IMREAD_ANYCOLOR)
                print("Converting RGB image to grayscale...")
                gray = cv2.cvtColor(img_, cv2.COLOR_BGR2GRAY)
                print("Converted RGB image to grayscale...")
                print("Resizing image to 28x28 scale...")
                img_ = cv2.resize(gray, (28, 28))
                print("Resized...")
                img_resized = cv2.imwrite(filename='saved_img-final.jpg', img=img_)
                print("Image saved!")

        #key = cv2.waitKey(1)
        key = cv2.waitKey(100)  # Wait 100 msec (just for testing).

        if key == ord('q'):
            print("Turning off camera.")
            print("Camera off.")
            print("Program ended.")
            break

    except(KeyboardInterrupt):
        print("Turning off camera.")
        print("Camera off.")
        print("Program ended.")
        break

webcam.release()
cv2.destroyAllWindows()