RecordWebcam.py

'''
For use in recording a usb camera mounted in a car
'''
import os
import time
import cv2

class RecordWebCam(object):

    def __init__(self,outPath,captureFrequency=5.0,camId=0,show=False):
        '''
        outPath: path where the images are to be stored
            Images will be stored as <epoch in milliseconds>.jpeg
        captureFrequency: the frequency in hertz to save a frame
        camId: the index of the usb camera to use, defaults to 1 but may need to change for multi camera machines
        show: bool, if the images should be shown as they are taken
        '''
        self.outPath = outPath
        self._checkOutPath()
        self.timeBetweenFrames = 1.0/captureFrequency
        self.show = show

        self.lastCapture = 0

        # create the video stream
        self.camId = camId
        self.cap = cv2.VideoCapture(camId)
        self.cap.set(cv2.CAP_PROP_FRAME_HEIGHT,720)
        self.cap.set(cv2.CAP_PROP_FRAME_WIDTH,1280)

        if show:
            self.windowName = "Captured Image"
            cv2.namedWindow("Captured Image",cv2.WINDOW_NORMAL)

        print("Finished setting up camera {}!".format(self.camId))

    def _checkOutPath(self):
        '''
        Verify that self.outPath is a directory
        '''
        if not os.path.isdir(self.outPath):
            os.makedirs(self.outPath)

    def __call__(self):
        '''
        when called cature and save a frame
        '''
        currentTime = time.time()       
        if currentTime - self.timeBetweenFrames > self.lastCapture:
            self.lastCapture = currentTime
            ret,frame = self.cap.read()
            assert ret, "Lost connection with camera {}!".format(self.camId)
            frame = cv2.flip(frame,-1)
            cv2.imwrite("{}/{:0.3f}.jpeg".format(self.outPath,currentTime),frame)
            if self.show:
                cv2.waitKey(1)
                cv2.imshow(self.windowName,frame)

    def shutDown(self):
        '''
        Shut down the recorder
        '''
        self.cap.release()
        if self.show:
            cv2.destroyAllWindows()