【Python】【OpenCV】视频帧和摄像头帧操作 and 窗口显示

一、读取写入视频文件

 1 import cv2 2  3 # 创建一个视屏捕获对象 4 videoCapture = cv2.VideoCapture('AVI.avi') 5  6 # 获取视频的属性值，cv2.CAP_PROP_FPS获取视频帧率 7 fps = videoCapture.get(cv2.CAP_PROP_FPS) 8  9 # cv2.CAP_PROP_FRAME_WIDTH/HEIGHT 返回float类型 获取视频帧的宽高10 size = int(videoCapture.get(cv2.CAP_PROP_FRAME_WIDTH)), \11        int(videoCapture.get(cv2.CAP_PROP_FRAME_HEIGHT))12 13 '''14 创建一个写入对象，将帧写入输出的视频15 cv2.VideoWriter_fourcc()函数指定编码器为 I42016 fps 和 size 指定输出的帧率和尺寸17 '''18 videoWrite = cv2.VideoWriter('Out.avi',19                              cv2.VideoWriter_fourcc('I', '4', '2', '0'),20                              fps, size21                              )22 23 '''24 对捕获到的视频对象进行读取帧，success表示是否成功读取一帧，frame表示当前帧。25 循环读取写入输出视频。26 '''27 success, frame = videoCapture.read()28 while success:29        videoWrite.write(frame)30        success, frame = videoCapture.read()

二、捕获摄像头帧

 1 import cv2 2  3 cameraCapture = cv2.VideoCapture(0) 4  5 fps = 30 6  7 size = int(cameraCapture.get(cv2.CAP_PROP_FRAME_WIDTH)), \ 8         int(cameraCapture.get(cv2.CAP_PROP_FRAME_HEIGHT)) 9 10 videoWriter = cv2.VideoWriter(11     'OutVideo_GRAB.avi',12     cv2.VideoWriter_fourcc('I', '4', '2', '0'),13     fps,14     size15 )16 17 success, frame = cameraCapture.read()18 19 numFramesRemaining = 10 * fps20 while success and numFramesRemaining > 0:21     videoWriter.write(frame)22     success, frame = cameraCapture.read()23     numFramesRemaining -= 1

和视频的读取写入没有什么差异，都是需要先创建一个VideoCapture Object来操作，下述是细微差别：

3 Line：VideoCapture(0)，其中 0 代表设备，还可以1，2，3 分别代表不同的摄像头（如果存在），也可以输入网络摄像头，直接替换成URL即可

5 Line：需要手动设置fps的值

19 Line：需要设定一个时间，numFramesRemaining代表持续捕获300个帧，而每30个帧为一秒，所以将生成一个10秒钟的视频文件

三、窗口显示图片

1 import cv22 3 img = cv2.imread('CopyPic.png')4 cv2.imshow('', img)5 cv2.waitKey()6 cv2.destroyAllWindows()

四、窗口显示摄像头

 1 import cv2 2  3 # 检测窗口是否被点击 4 clicked = False 5  6  7 # 定义鼠标事件处理函数 8 def onMouse(event: int, x, y, flags, param): 9     global clicked10     if event == cv2.EVENT_LBUTTONUP:11         clicked = True12 13 14 # 创建一个视频对象15 cameraCapture = cv2.VideoCapture(0)16 # 定义窗口命17 cv2.namedWindow('Camera')18 # 将鼠标回调函数，将鼠标事件处理函数和窗口关联起来19 cv2.setMouseCallback('Camera', onMouse)20 21 print('Showing camera feed. Click window or press any key to stop.')22 # 获取当前时间的摄像头帧23 success, frame = cameraCapture.read()24 25 # 循环获取当前时间的摄像头帧，当按下任意按键 or 点击鼠标时则停止显示26 while success and cv2.waitKey(1) == -1 and not clicked:27     cv2.imshow('Camera', frame)28     success, frame = cameraCapture.read()29 30 # 关闭窗口31 cv2.destroyAllWindows()32 33 # 释放摄像头资源34 cameraCapture.release()

针对多摄像头，我们需要先探明摄像头的设备号：

 1 import cv2 2  3 for item in range(10): 4     # 创建一个object 5     camera = cv2.VideoCapture(item) 6  7     # 查询此摄像头是否能打开，如果不能则跳过，并输出一条 Error Message 8     if not camera.isOpened(): 9         print(f"Can\'t open camera {item}")10         continue11 12     # 读取摄像头帧率13     while True:14         success, frame = camera.read()15         # 当摄像头帧读取失败则跳过16         if not success:17             break18 19         cv2.imshow(f'Camera device number: {item}', frame)20 21         # 等待1毫秒，检查用户是否有键盘输入‘q’22         if cv2.waitKey(1) == ord('q'):23             break24 25     camera.release()26     cv2.destroyAllWindows()