python - 如何使用OpenCV更改视频中的单个帧？

Question

我有一个使用OpenCV VideoWriter构建的视频。

我想用一个不同的框架来改变一个特定的框架。
有没有一种方法可以在不重建整个视频的情况下进行操作？

Answer 1

我通过将所有像素都设为零来更改第三帧。

import numpy as np
import cv2

cap = cv2.VideoCapture(0)
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))

frame_number = -1

while(True):
    frame_number += 1
    ret, frame = cap.read()
    if frame_number == 3:  # if frame is the third frame than replace it with blank drame
      change_frame_with = np.zeros_like(frame)
      frame = change_frame_with
    out.write(frame)

    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    cv2.imshow('frame',gray)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
out.release()
cv2.destroyAllWindows()

如果您不想再次浏览所有帧:

import numpy as np
import cv2

cap = cv2.VideoCapture(0)
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))

frame_number = -1

while(True):
    frame_number += 1
    ret, frame = cap.read()
    if frame_number == 3:  # if frame is the third frame than replace it with blank drame
      change_frame_with = np.zeros_like(frame)
      frame = change_frame_with
      out.write(frame)
      break                # add a break here
    else:
      out.write(frame)

    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    cv2.imshow('frame',gray)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
out.release()
cv2.destroyAllWindows()

但是上述解决方案不会将3之后的所有其他帧写入整个新视频