opencv 实现对视频帧的提取，包括从摄像头获取视频及avi文件获取视频-opencv achieve the extraction of video frames, including video from the camera and get access to video avi files

分析视频文件，得到关键帧，并从关键帧中识别出圆形物体（应用为识别柑橘）-Analysis of video files, get the key frames and key frames from the identified circular object (application for the identification of citrus)

该段代码主要是获取图像的像素并写入本地文件中，包括灰度图和三通道图。-This code is mainly to get the image pixels and write local files, including grayscale and three-channel map.

从摄像头得到视频流，从中任意选取5帧，保存成图像文件 2.从AVI文件读取视频，从中任意选取5帧，保存成图像文件 3.从摄像头得到视频流，在指定的窗口内实时显示该视频 4. 读取一jpg文件，对其旋转、缩放，然后显示出来 -Get a video stream a camera, which arbitrarily selected five, save it as an image file 2. Read the video AVI files, arbitrarily