python - 将视频中检测到的边缘帧保存为视频(opencv)

Question

我想将边缘检测到的帧保存为视频。我可以预览视频的帧，但输出视频不播放。

cap = cv2.VideoCapture("video.mp4")

fourcc = cv2.VideoWriter_fourcc(*'MP4V')

out = cv2.VideoWriter('output.mp4', fourcc, 23.976, (1280,720))

while(cap.isOpened()):
    ret, frame = cap.read()
    edges = cv.Canny(frame,50,50)
    out.write(edges)
    cv2.imshow('frame', edges)
    c = cv2.waitKey(1)
    if c & 0xFF == ord('q'):
        break

cap.release()
out.release()

Answer 1

我想解决三个问题。

您正在申请Canny到每个视频帧。输出大小是多少:

print(edges.shape)
(720, 1280)

维度720, 1280表示该帧是一个灰度值。如果框架是彩色图像，则尺寸将为 (720, 1080, 3)对于每个 channel R、G、B。

因此你需要初始化你的VideoWriter对象作为 grey-scale图片。

out = cv2.VideoWriter('output.mp4', fourcc, 23.976, (1280,720), isColor=False)

确保您正在捕获下一帧:

ret, frame = cap.read()
if ret:
    edges = cv.Canny(frame,50,50)
    .
    .

确保您的框架与 VideoWriter 的尺寸相同。对象

while cap.isOpened():
ret, frame = cap.read()
if ret:
    edges = cv2.Canny(frame, 50, 50)
    edges = cv2.resize(edges, (1280, 720))
    out.write(edges)
    .
    .

代码:

import cv2

cap = cv2.VideoCapture("video.mp4")

fourcc = cv2.VideoWriter_fourcc(*"mp4v")

out = cv2.VideoWriter('output.mp4', fourcc, 23.976, (1280, 720), isColor=False)

while cap.isOpened():
    ret, frame = cap.read()
    if ret:
        edges = cv2.Canny(frame, 50, 50)
        edges = cv2.resize(edges, (1280, 720))
        out.write(edges)
        cv2.imshow('frame', edges)
        c = cv2.waitKey(1)
        if c & 0xFF == ord('q'):
            break
    else:
        break

cap.release()
out.release()