opencv的python教程代码第1课

import cv2 import numpy import time class CaptureManager(object): def __init__(self, capture, previewWindowManager = None, shouldMirrorPreview = False): self.previewWindowManager = previewWindowManager self.shouldMirrorPreview = shouldMirrorPreview self._capture = capture self._channel = 0 self._enteredFrame = False self._frame = None self._imageFilename = None self._videoFilename = None self._videoEncoding = None self._videoWriter = None self._startTime = None self._framesElapsed = 0 self._fpsEstimate = None @property def channel(self): return self._channel @channel.setter def channel(self, value): if self._channel != value: self._channel = value self._frame = None @property def frame(self): if self._enteredFrame and self._frame is None: _, self._frame = self._capture.retrieve( self._frame, self.channel) return self._frame @property def isWritingImage(self): return self._imageFilename is not None @property def isWritingVideo(self): return self._videoFilename is not None def enterFrame(self): """Capture the next frame, if any.""" # But first, check that any previous frame was exited. assert not self._enteredFrame, \ 'previous enterFrame() had no matching exitFrame()' if self._capture is not None: self._enteredFrame = self._capture.grab() def exitFrame(self): """Draw to the window. Write to files. Release the frame.""" # Check whether any grabbed frame is retrievable. # The getter may retrieve and cache the frame. if self.frame is None: self._enteredFrame = False return # Update the FPS estimate and related variables. if self._framesElapsed == 0: self._startTime = time.time() else: timeElapsed = time.time() - self._startTime self._fpsEstimate = self._framesElapsed / timeElapsed self._framesElapsed += 1 # Draw to the window, if any. if self.previewWindowManager is not None: if self.shouldMirrorPreview: mirroredFrame = numpy.fliplr(self._frame) self.previewWindowManager.show(mirroredFrame) else: self.previewWindowManager.show(self._frame) # Write to the image pythonfile, if any. if self.isWritingImage: cv2.imwrite(self._imageFilename, self._frame) self._imageFilename = None # Write to the video pythonfile, if any. self._writeVideoFrame() # Release the frame. self._frame = None self._enteredFrame = False def writeImage(self, filename): """Write the next exited frame to an image pythonfile.""" self._imageFilename = filename def startWritingVideo( self, filename, encoding = cv2.VideoWriter_fourcc('M','J','P','G')): """Start writing exited frames to a video pythonfile.""" self._videoFilename = filename self._videoEncoding = encoding def stopWritingVideo(self): """Stop writing exited frames to a video pythonfile.""" self._videoFilename = None self._videoEncoding = None self._videoWriter = None def _writeVideoFrame(self): if not self.isWritingVideo: return if self._videoWriter is None: fps = self._capture.get(cv2.CAP_PROP_FPS) if fps <= 0.0: # The capture's FPS is unknown so use an estimate. if self._framesElapsed < 20: # Wait until more frames elapse so that the # estimate is more stable. return else: fps = self._fpsEstimate size = (int(self._capture.get( cv2.CAP_PROP_FRAME_WIDTH)), int(self._capture.get( cv2.CAP_PROP_FRAME_HEIGHT))) self._videoWriter = cv2.VideoWriter( self._videoFilename, self._videoEncoding, fps, size) self._videoWriter.write(self._frame) class WindowManager(object): def __init__(self, windowName, keypressCallback = None): self.keypressCallback = keypressCallback self._windowName = windowName self._isWindowCreated = False @property def isWindowCreated(self): return self._isWindowCreated def createWindow(self): cv2.namedWindow(self._windowName) self._isWindowCreated = True def show(self, frame): cv2.imshow(self._windowName, frame) def destroyWindow(self): cv2.destroyWindow(self._windowName) self._isWindowCreated = False def processEvents(self): keycode = cv2.waitKey(1) if self.keypressCallback is not None and keycode != -1: self.keypressCallback(keycode)