小编AMT*_*MTQ的帖子

我正在使用Python 2.7和OpenCV 3.1.0开发openCV的光流教程,并且有一个关于使用cv2.line()的问题.以下是带有突出显示部分的原始代码:

import numpy as np
import cv2

cap = cv2.VideoCapture('slow.flv')

# params for ShiTomasi corner detection
feature_params = dict( maxCorners = 100,
                       qualityLevel = 0.3,
                       minDistance = 7,
                       blockSize = 7 )

# Parameters for lucas kanade optical flow
lk_params = dict( winSize  = (15,15),
                  maxLevel = 2,
                  criteria = (cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 10, 0.03))

# Create some random colors
color = np.random.randint(0,255,(100,3))

# Take first frame and find corners in it
ret, old_frame …

我正在使用 ffmpeg 从视频中提取帧。一切正常，但有些事情似乎很奇怪：输出的编号始终以 0001 而不是 0000 开头。在最小工作示例下面，是控制台的输出和生成的帧的图片。我在Win10上使用Windows shell。

ffmpeg -i P1390752.MP4 -vframes 4 frame%%04d.png

控制台输出：

C:\Users\xxxx>ffmpeg -i P1390752.MP4 -vframes 4 frame%04d.png
ffmpeg version git-2020-01-15-0dc0837 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.2.1 (GCC) 20200111
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec …