【Python】【OpenCV】Cameo项目(一)实时显示摄像头帧

 Cameo项目介绍:

1、实时捕获并显示摄像头帧。

2、具备截图、保存视频和退出三个功能键

 要求存在文件:manager.py 和 cameo.py

 

一、manager.py

两个类:CaptureManager、WindowManager

  CaptureManager负责摄像头帧的捕获编解码得到实际帧当前帧保存为图片一段时间内的帧保存为视频这四个核心功能。

  CaptureManager负责窗口的创建窗口展示当前画面三个功能键的交互关闭窗口释放资源这四个个功能

 

二、cameo.py

程序入口,关联调用CaptureManager和CaptureManager,并定义三个功能键

 

详细方法实现参照下述代码和注释

manager.py

 

  1 from __future__ import annotations
  2 import cv2
  3 import numpy
  4 import time
  5 
  6 '''
  7 1、允许同一文件下不同类之间的类型提示,py3.7以上特性
  8 2、cv2——获取摄像头和展示
  9 3、numpy——对展示画面进行左右翻转(fliplr)
 10 4、time——精确获取时间间隔,然后计算帧率估值
 11 '''
 12 
 13 
 14 class CaptureManager:
 15     def __init__(self, capture: cv2.VideoCapture,
 16                  previewWindowManager: WindowManager = None,
 17                  shouldMirrorPreview: bool = False):
 18         self.previewWindowManager = previewWindowManager
 19         self.shouldMirrorPreview = shouldMirrorPreview
 20 
 21         self._capture = capture
 22         self._channel = 0
 23         self._enteredFrame = False
 24         self._frame = None
 25 
 26         self._imageFilename = None
 27         self._videoFilename = None
 28         self._videoEncoding = None
 29         self._videoWriter = None
 30 
 31         self._startTime = None
 32         self._framesElapsed = 0
 33         self._fpsEstimate = None
 34 
 35     @property
 36     def channel(self):
 37         return self._channel
 38 
 39     @channel.setter
 40     def channel(self, value):
 41         if self._channel != value:
 42             self._channel = value
 43             self._frame = None  # 对通道赋值时需要将当前帧置空,否则可能出现通道为未更改现象
 44 
 45     # 如果进入帧,且当前帧为None则对已捕获的帧进行解码和获取实际图像帧
 46     @property
 47     def frame(self):
 48         if self._enteredFrame and self._frame is None:
 49             _, self._frame = self._capture.retrieve(self._frame, self.channel)
 50         return self._frame
 51 
 52     @property
 53     def isWritingImage(self):
 54         return self._imageFilename is not None
 55 
 56     @property
 57     def isWritingVideo(self):
 58         return self._videoFilename is not None
 59 
 60     def enterFrame(self):
 61         # 检查上一帧是否被处理完,如未处理完,则会被下一帧覆盖,最终导致实时画面或者保存的视频不连续
 62         assert not self._enteredFrame, 'previous enterFrame() had no matching exitFrame()'
 63 
 64         if self._capture is not None:
 65             self._enteredFrame = self._capture.grab()
 66 
 67     def exitFrame(self):
 68         # 如果当前帧为None,表示未成功捕获有效帧或视频流已处理完成,此时则直接结束此方法
 69         if self.frame is None:
 70             self._enteredFrame = False
 71             return
 72 
 73         # 更新FPS估值
 74         if self._framesElapsed == 0:
 75             self._startTime = time.perf_counter()
 76         else:
 77             timeElapsed = time.perf_counter() - self._startTime
 78             self._fpsEstimate = self._framesElapsed / timeElapsed
 79         self._framesElapsed += 1
 80 
 81         # 是否水平反转画面并展示
 82         if self.previewWindowManager is not None:
 83             if self.shouldMirrorPreview:
 84                 mirroredFrame = numpy.fliplr(self._frame)
 85                 self.previewWindowManager.show(mirroredFrame)
 86             else:
 87                 self.previewWindowManager.show(self._frame)
 88 
 89         # 将当前帧保存为图片
 90         if self.isWritingImage:
 91             cv2.imwrite(self._imageFilename, self._frame)
 92             self._imageFilename = None
 93 
 94         # 将当前帧写入视频
 95         self._writeVideoFrame()
 96 
 97         # 释放并退出当前帧
 98         self._frame = None
 99         self._enteredFrame = False
100 
101     def writeImage(self, filename):
102         self._imageFilename = filename
103 
104     def startWritingVideo(self, filename, encoding=cv2.VideoWriter_fourcc('M', 'J', 'P', 'G')):
105         self._videoFilename = filename
106         self._videoEncoding = encoding
107 
108     def stopWritingVideo(self):
109         self._videoFilename = None
110         self._videoEncoding = None
111         self._videoWriter = None
112 
113     def _writeVideoFrame(self):
114         if not self.isWritingVideo:
115             return
116 
117         # 检查是否创建了VideoWriter对象
118         if self._videoWriter is None:
119             # 获取摄像头帧率
120             fps = self._capture.get(cv2.CAP_PROP_FPS)
121             # 如果帧率获取失败则使用估计值
122             if numpy.isnan(fps) or fps <= 0.0:
123                 # 获取更多的以处理帧数,以求得更稳定的帧率
124                 if self._framesElapsed < 20:
125                     return
126                 else:
127                     fps = self._fpsEstimate
128             size = (int(self._capture.get(
129                 cv2.CAP_PROP_FRAME_WIDTH)),
130                     int(self._capture.get(
131                         cv2.CAP_PROP_FRAME_HEIGHT)))
132             self._videoWriter = cv2.VideoWriter(
133                 self._videoFilename, self._videoEncoding,
134                 fps, size)
135 
136         self._videoWriter.write(self._frame)
137 
138 
139 class WindowManager(object):
140 
141     def __init__(self, windowName: str
142                  , keypressCallback=None):
143         self.keypressCallback = keypressCallback
144 
145         self._windowName = windowName
146         self._isWindowCreated = False
147 
148     @property
149     def isWindowCreated(self):
150         return self._isWindowCreated
151 
152     def createWindow(self):
153         cv2.namedWindow(self._windowName)
154         self._isWindowCreated = True
155 
156     def show(self, frame):
157         cv2.imshow(self._windowName, frame)
158 
159     def destroyWindow(self):
160         cv2.destroyWindow(self._windowName)
161         self._isWindowCreated = False
162 
163     def processEvents(self):
164         keycode = cv2.waitKey(1)
165         if self.keypressCallback is not None and keycode != -1:
166             self.keypressCallback(keycode)
View Code

 

 

 

cameo.py

 

 1 import cv2
 2 from managers import WindowManager, CaptureManager
 3 
 4 
 5 class Cameo:
 6     def __init__(self):
 7         self._windowManager = WindowManager('Cameo',
 8                                             self.onKeypress)
 9         self._captureManager = CaptureManager(
10             cv2.VideoCapture(0), self._windowManager, True)
11 
12     def run(self):
13         # 创建窗口
14         self._windowManager.createWindow()
15         while self._windowManager.isWindowCreated:
16             # 开始捕获摄像头帧
17             self._captureManager.enterFrame()
18             # 解码并获取实际帧
19             frame = self._captureManager.frame
20             # 预留后续新功能
21             if frame is not None:
22                 pass
23             # 写入图片文件或者视频文件并释放帧资源
24             self._captureManager.exitFrame()
25             # 检查并返回键盘状态
26             self._windowManager.processEvents()
27 
28     def onKeypress(self, keycode):
29         if keycode == 32:  # space
30             self._captureManager.writeImage(r'screenshot.png')
31         elif keycode == 9:  # tab
32             if not self._captureManager.isWritingVideo:
33                 self._captureManager.startWritingVideo('screencast.avi')
34             else:
35                 self._captureManager.stopWritingVideo()
36         elif keycode == 27:  # escape
37             self._windowManager.destroyWindow()
38 
39 
40 if __name__ == "__main__":
41     Cameo().run()
View Code

 

热门相关:龙印战神   重生复仇:腹黑千金不好惹   觅仙道   跟总裁假结婚的日子   危险的叔叔