Capture webcam video using PyQt

Question

Given the following PyQt code, I can perfectly capture the webcam's streaming video.

Now, I want to modify code, so a button named ''capture'' button is added that once pressed captures the streaming video and saves the image. How can I do this?

The obtained small image will be used to query an object recognition server.

import sys
from PyQt4 import QtGui, QtCore
import cv2

class QtCapture(QtGui.QWidget):
    def __init__(self, *args):
        super(QtGui.QWidget, self).__init__()

        self.fps = 24
        self.cap = cv2.VideoCapture(*args)

        self.video_frame = QtGui.QLabel()
        lay = QtGui.QVBoxLayout()
        lay.setMargin(0)
        lay.addWidget(self.video_frame)
        self.setLayout(lay)

    def setFPS(self, fps):
        self.fps = fps

    def nextFrameSlot(self):
        ret, frame = self.cap.read()
        # My webcam yields frames in BGR format
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        img = QtGui.QImage(frame, frame.shape[1], frame.shape[0], QtGui.QImage.Format_RGB888)
        pix = QtGui.QPixmap.fromImage(img)
        self.video_frame.setPixmap(pix)

    def start(self):
        self.timer = QtCore.QTimer()
        self.timer.timeout.connect(self.nextFrameSlot)
        self.timer.start(1000./self.fps)

    def stop(self):
        self.timer.stop()

    def deleteLater(self):
        self.cap.release()
        super(QtGui.QWidget, self).deleteLater()


class ControlWindow(QtGui.QWidget):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.capture = None

        self.start_button = QtGui.QPushButton('Start')
        self.start_button.clicked.connect(self.startCapture)
        self.quit_button = QtGui.QPushButton('End')
        self.quit_button.clicked.connect(self.endCapture)
        self.end_button = QtGui.QPushButton('Stop')

        vbox = QtGui.QVBoxLayout(self)
        vbox.addWidget(self.start_button)
        vbox.addWidget(self.end_button)
        vbox.addWidget(self.quit_button)
        self.setLayout(vbox)
        self.setWindowTitle('Control Panel')
        self.setGeometry(100,100,200,200)
        self.show()

    def startCapture(self):
        if not self.capture:
            self.capture = QtCapture(0)
            self.end_button.clicked.connect(self.capture.stop)
            # self.capture.setFPS(1)
            self.capture.setParent(self)
            self.capture.setWindowFlags(QtCore.Qt.Tool)
        self.capture.start()
        self.capture.show()

    def endCapture(self):
        self.capture.deleteLater()
        self.capture = None


if __name__ == '__main__':

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

Insuppressible

I also need to save the streaming video into file as separate frame images. I could do it by adding this qPixmap = pix.save('image.jpg'). However this saves only on image not the sequence of images – Insuppressible

I do not completely understand what you are trying to accomplish. As you said, pix.save('image.jpg') saves the image, doing that multiple times, saves multiple images. In what format do you want the 'sequence of images' to be? – Hydrochloride

Answer 1

I added the "Capture" button, and placed a switch in the nextFrameSlot() method of the QtCapture class. Hope it will work as you expected.

import sys
from PyQt4 import QtGui, QtCore
import cv2

class QtCapture(QtGui.QWidget):
    def __init__(self, *args):
        super(QtGui.QWidget, self).__init__()

        self.fps = 24
        self.cap = cv2.VideoCapture(*args)

        self.video_frame = QtGui.QLabel()
        lay = QtGui.QVBoxLayout()
        lay.setMargin(0)
        lay.addWidget(self.video_frame)
        self.setLayout(lay)

        # ------ Modification ------ #
        self.isCapturing = False
        self.ith_frame = 1
        # ------ Modification ------ #

    def setFPS(self, fps):
        self.fps = fps

    def nextFrameSlot(self):
        ret, frame = self.cap.read()

        # ------ Modification ------ #
        # Save images if isCapturing
        if self.isCapturing:
            cv2.imwrite('img_%05d.jpg'%self.ith_frame, frame)
            self.ith_frame += 1
        # ------ Modification ------ #

        # My webcam yields frames in BGR format
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        img = QtGui.QImage(frame, frame.shape[1], frame.shape[0], QtGui.QImage.Format_RGB888)
        pix = QtGui.QPixmap.fromImage(img)
        self.video_frame.setPixmap(pix)

    def start(self):
        self.timer = QtCore.QTimer()
        self.timer.timeout.connect(self.nextFrameSlot)
        self.timer.start(1000./self.fps)

    def stop(self):
        self.timer.stop()

    # ------ Modification ------ #
    def capture(self):
        if not self.isCapturing:
            self.isCapturing = True
        else:
            self.isCapturing = False
    # ------ Modification ------ #

    def deleteLater(self):
        self.cap.release()
        super(QtGui.QWidget, self).deleteLater()


class ControlWindow(QtGui.QWidget):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.capture = None

        self.start_button = QtGui.QPushButton('Start')
        self.start_button.clicked.connect(self.startCapture)
        self.quit_button = QtGui.QPushButton('End')
        self.quit_button.clicked.connect(self.endCapture)
        self.end_button = QtGui.QPushButton('Stop')

        # ------ Modification ------ #
        self.capture_button = QtGui.QPushButton('Capture')
        self.capture_button.clicked.connect(self.saveCapture)
        # ------ Modification ------ #

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

        # ------ Modification ------ #
        vbox.addWidget(self.capture_button)
        # ------ Modification ------ #

        self.setLayout(vbox)
        self.setWindowTitle('Control Panel')
        self.setGeometry(100,100,200,200)
        self.show()

    def startCapture(self):
        if not self.capture:
            self.capture = QtCapture(0)
            self.end_button.clicked.connect(self.capture.stop)
            # self.capture.setFPS(1)
            self.capture.setParent(self)
            self.capture.setWindowFlags(QtCore.Qt.Tool)
        self.capture.start()
        self.capture.show()

    def endCapture(self):
        self.capture.deleteLater()
        self.capture = None

    # ------ Modification ------ #
    def saveCapture(self):
        if self.capture:
            self.capture.capture()
    # ------ Modification ------ #



if __name__ == '__main__':

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

Audiometer

I've been trying to understand for forever why my program doesn't work, I didn't have a timer and my program lagged badly, thank you so much. – Farnesol