OpenCV Video Capture with PyQt4

Question

I have been trying to capture video using PyQt4 GUI and OpenCV. I created some buttons like "Start", "End" etc to control the capturing. Starting is fine, but I can't stop the capture. To stop the capture, I need to break the while loop in startCapture() function below, I couldn't achieve it.

Currently, endCapture() destroys the window, but startCapture while loop simply creates it and continue the capturing. Only option is to break that loop.

Below is the code I used:

import cv2
import numpy as np
from PyQt4 import QtGui, QtCore

def startCapture(cap):
    print "pressed start"
    while(True):
        ret, frame = cap.read()
        cv2.imshow("Capture", frame)
        cv2.waitKey(5)
    cv2.destroyAllWindows() 

def endCapture(cap):
    print "pressed End"
    cv2.destroyAllWindows()

def quitCapture(cap):
    print "pressed Quit"
    cv2.destroyAllWindows()
    cap.release()
    QtCore.QCoreApplication.quit()

class Window(QtGui.QWidget):
    def __init__(self):

        c = cv2.VideoCapture(0)

        QtGui.QWidget.__init__(self)
        self.setWindowTitle('Control Panel')

        self.start_button = QtGui.QPushButton('Start',self)
        self.start_button.clicked.connect(lambda : startCapture(c, True))

        self.end_button = QtGui.QPushButton('End',self)
        self.end_button.clicked.connect(lambda : endCapture(c))

        self.quit_button = QtGui.QPushButton('Quit',self)
        self.quit_button.clicked.connect(lambda : quit(c))

        vbox = QtGui.QVBoxLayout(self)
        vbox.addWidget(self.start_button)
        vbox.addWidget(self.end_button)
        vbox.addWidget(self.quit_button)

        self.setLayout(vbox)
        self.setGeometry(100,100,200,200)
        self.show()

if __name__ == '__main__':

    import sys
    app = QtGui.QApplication(sys.argv)
    window = Window()
    sys.exit(app.exec_())

Can any one suggest how to break that loop and exit the capturing?

Answer 1

class Capture():
    def __init__(self):
        self.capturing = False
        self.c = cv2.VideoCapture(0)

    def startCapture(self):
        print "pressed start"
        self.capturing = True
        cap = self.c
        while(self.capturing):
            ret, frame = cap.read()
            cv2.imshow("Capture", frame)
            cv2.waitKey(5)
        cv2.destroyAllWindows()

    def endCapture(self):
        print "pressed End"
        self.capturing = False
        # cv2.destroyAllWindows()

    def quitCapture(self):
        print "pressed Quit"
        cap = self.c
        cv2.destroyAllWindows()
        cap.release()
        QtCore.QCoreApplication.quit()

in Window:

self.capture = Capture()
self.start_button = QtGui.QPushButton('Start',self)
self.start_button.clicked.connect(self.capture.startCapture)

self.end_button = QtGui.QPushButton('End',self)
self.end_button.clicked.connect(self.capture.endCapture)

self.quit_button = QtGui.QPushButton('Quit',self)
self.quit_button.clicked.connect(self.capture.quitCapture)