VideoWriter.write中的Python OpenCV错误(-215)

问题描述

我正在尝试编写python3-opencv3代码以读取彩色视频并将其转换为灰度并保存回去.(尝试练习以学习python& opencv)

I am trying to a write a python3-opencv3 code to read the color video and convert it to grayscale and save it back.(Trying exercises to learn python & opencv)

在ubuntu中工作时，我发现cv2.VideoCapture isColor标志不起作用(仅适用于Windows)

As I am working in ubuntu, I found out cv2.VideoCapture isColor flag will not work (it works only windows)

import numpy as np
import cv2
cap = cv2.VideoCapture('output.avi')
ret, frame = cap.read()
print('ret =', ret, 'W =', frame.shape[1], 'H =', frame.shape[0], 'channel =', frame.shape[2])
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
height, width = gray.shape[:2]
print(height,width)
cv2.imshow('frame',gray)
FPS= 20.0
FrameSize=(frame.shape[1], frame.shape[0])
fourcc = cv2.VideoWriter_fourcc(*'MJPG')
out = cv2.VideoWriter('Video_output.avi', fourcc, FPS, (width,height))

while(ret):
    ret, frame = cap.read()
    if cv2.waitKey(1) & 0xFF == ord('q') or ret == False:
        break
    print('ret =', ret, 'W =', frame.shape[1], 'H =', frame.shape[0], 'channel =', frame.shape[2])
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    # Save the video
    out.write(gray)
    cv2.imshow('frame',gray)
cap.release()
out.release()
cv2.destroyAllWindows()

---

这是给我的错误:(-215)img.cols == width&& img.rows == height * 3在函数写入中

---

It is give me thiserror: (-215) img.cols == width && img.rows == height*3 in function write

我正在猜测，问题出在帧大小和灰度图像转换上，但我无法弄清楚?我尝试了不同的高度和高度组合.虽然无法执行程序.

I am guessing, the problem is with framesize and grayscale image conversion but I am not able to figure out ? I have tried different combination of height & widht but none are able execute the program correctly.

有人可以帮忙吗?

根据评论的要求:

Traceback (most recent call last):
  File "/home/akash/Coded/VideoCode/Test3", line 70, in <module>
    out.write(gray)
cv2.error: /home/travis/miniconda/conda-bld/conda_1486587069159/work/opencv-3.1.0/modules/videoio/src/cap_mjpeg_encoder.cpp:834: error: (-215) img.cols == width && img.rows == height*3 in function write

推荐答案

OpenCV错误-215表示声明失败".断言本身已在消息中列出(短语断言失败"本身也可能也应如此；您可以在OpenCV的错误跟踪器中打开与此有关的故障单). (更新:我对此更改的拉取请求已于06.03 接受，并在opencv 3.4.2.)

OpenCV error -215 means "assertion failed". The assertion itself is listed in the message (the phrase "Assertion failed" itself probably should, too; you can open a ticket about this in OpenCV's bug tracker). (Update: my pull request with this change was accepted on 06.03 and was released in opencv 3.4.2.)

正如可以从断言中得出的那样，它希望帧是3色通道的帧.要制作灰度视频，您需要将isColor=False传递给构造函数:

As one can deduce from the assertion, it expects the frame to be a 3-color-channel one. To make a grayscale video, you need to pass isColor=False to VideoWriter constructor:

out = cv2.VideoWriter('Video_output.avi', fourcc, FPS, (width,height), False)

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