使用 OpenCV 将视频旋转 180 Python

Question

我是一个 python 初学者，对于我的错误提前表示歉意。我正在尝试将视频旋转 180 度，然后处理我本应创建的视频。

目前我正在这样做：

import cv2
import numpy as np
    
#that's my original video - the one that I want to rotate 180 degrees 

cap = cv2.VideoCapture('/Users/name/Desktop/VIDEO 12.05/PIC_P01.mp4')
    
    frame_number = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
    
    # Original Frames
    frames = []
    for i in range(frame_number):
        ret, frame = cap.read()
        frames.append(frame)

    #here's where I try to rotate the video 
    new = cv2.rotate(frame, cv2.ROTATE_180)
    
    cv2.imshow('output', new)
     if cv2.waitKey(1) & 0xFF == ord('q'):
                break

    #here I'm trying to write the new rotated video
    newvideoR = cv2.VideoWriter('PIC_P01R.mp4',0x7634706d, 50, (360, 640))
    for jj in range(len(new)):
        newvideoR.write(new[jj])
    newvideoR.release()
    cap.release()

然而，最后，当我去读取文件时，我发现只有一个我无法打开的空文件。由此，我推断我所做的步骤有误。有人对我该怎么做有什么建议吗？

** 我也尝试更改 cv2.Videowriter 上的参数（例如 fps、大小）但仍然无法正常工作

Answer 1

帧不用累加，再循环写。
您可以读取一帧，旋转它，并在同一个循环中写入它。

获取宽高：

 frame_width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
 frame_height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

循环前打开输出视频文件：

 newvideoR = cv2.VideoWriter('output.mp4', cv2.VideoWriter_fourcc(*"mp4v"), 50, (frame_width, frame_height))

读帧，旋转，循环写入：

 for i in range(frame_number):
     ret, frame = cap.read()

     new = cv2.rotate(frame, cv2.ROTATE_180)

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

     newvideoR.write(new)

发布视频reader和作者：
```
 newvideoR.release()
 cap.release()
```

完整代码示例（我将文件命名为 input.mp4 和 output.mp4）：

import cv2
    
#that's my original video - the one that I want to rotate 180 degrees 
cap = cv2.VideoCapture('input.mp4')
    
frame_number = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))

# Get width and height
frame_width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
frame_height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

# here I'm trying to write the new rotated video
# Open the output video file before the loop, cv2.VideoWriter_fourcc(*"mp4v") = 0x7634706d
newvideoR = cv2.VideoWriter('output.mp4', cv2.VideoWriter_fourcc(*"mp4v"), 50, (frame_width, frame_height))
    
# Original Frames
#frames = []
for i in range(frame_number):
    ret, frame = cap.read()
    #frames.append(frame)  # No need to append the original frames

    #here's where I try to rotate the video 
    new = cv2.rotate(frame, cv2.ROTATE_180)
    
    cv2.imshow('output', new)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

    newvideoR.write(new)

newvideoR.release()
cap.release()

使用 OpenCV 将视频旋转 180 Python

Rotate video 180 with OpenCV Python

python

video

opencv

video-capture

rotation