PyQt showing video stream from opencv

问题:

Try to link PyQt and Opencv video feed, can't understand how to apply while loop for continuously streaming video. It just take a still picture.Please can anyone help to solve the problem.

• PtQt=5

• Python=3.6.1

---

class App(QWidget):
    def __init__(self):
        super().__init__()
        self.title = 'PyQt5 Video'
        self.left = 100
        self.top = 100
        self.width = 640
        self.height = 480
        self.initUI()


    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.resize(1800, 1200)
        #create a label
        label = QLabel(self)
        cap = cv2.VideoCapture(0)
        ret, frame = cap.read()
        rgbImage = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        convertToQtFormat = QtGui.QImage(rgbImage.data, rgbImage.shape[1], rgbImage.shape[0],
                                         QtGui.QImage.Format_RGB888)
        convertToQtFormat = QtGui.QPixmap.fromImage(convertToQtFormat)
        pixmap = QPixmap(convertToQtFormat)
        resizeImage = pixmap.scaled(640, 480, QtCore.Qt.KeepAspectRatio)
        QApplication.processEvents()
        label.setPixmap(resizeImage)
        self.show()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())

回答1:

The problem is that the function that obtains the image is executed only once and not updating the label.
The correct way is to place it inside a loop, but it will result in blocking the main window. This blocking of main window can be solved by using the QThread class and send through a signal QImage to update the label. For example:

class Thread(QThread):
    changePixmap = pyqtSignal(QImage)

    def run(self):
        cap = cv2.VideoCapture(0)
        while True:
            ret, frame = cap.read()
            if ret:
                # https://stackoverflow.com/a/55468544/6622587
                rgbImage = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
                h, w, ch = rgbImage.shape
                bytesPerLine = ch * w
                convertToQtFormat = QtGui.QImage(rgbImage.data, w, h, bytesPerLine, QtGui.QImage.Format_RGB888)
                p = convertToQtFormat.scaled(640, 480, Qt.KeepAspectRatio)
                self.changePixmap.emit(p)


class App(QWidget):
    def __init__(self):
        super().__init__()
        [...]
        self.initUI()

    @pyqtSlot(QImage)
    def setImage(self, image):
        self.label.setPixmap(QPixmap.fromImage(image))

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.resize(1800, 1200)
        # create a label
        self.label = QLabel(self)
        self.label.move(280, 120)
        self.label.resize(640, 480)
        th = Thread(self)
        th.changePixmap.connect(self.setImage)
        th.start()

回答2:

Thank you Taimur Islam for the question. Thank you eyllanesc for wonderful answering and I have modified your code little bit. I used PtQt=4 Python=2.7 and I didn't use opencv

import sys    
import numpy as np
import flycapture2 as fc2

from PyQt4.QtCore import (QThread, Qt, pyqtSignal)
from PyQt4.QtGui import (QPixmap, QImage, QApplication, QWidget, QLabel)

class Thread(QThread):
    changePixmap = pyqtSignal(QImage)

    def __init__(self, parent=None):
        QThread.__init__(self, parent=parent)       
        self.cameraSettings()


    def run(self):      
        while True:
            im = fc2.Image()
            self.c.retrieve_buffer(im)
            a = np.array(im)    

            rawImage = QImage(a.data, a.shape[1], a.shape[0], QImage.Format_Indexed8)

            self.changePixmap.emit(rawImage)

    def cameraSettings(self):
        print(fc2.get_library_version())
        self.c = fc2.Context()
        numberCam = self.c.get_num_of_cameras()
        print(numberCam)    
        self.c.connect(*self.c.get_camera_from_index(0))
        print(self.c.get_camera_info())
        m, f = self.c.get_video_mode_and_frame_rate()
        print(m, f)
        print(self.c.get_property_info(fc2.FRAME_RATE))
        p = self.c.get_property(fc2.FRAME_RATE)
        print(p)
        self.c.set_property(**p)
        self.c.start_capture()


class App(QWidget):
    def __init__(self):
            super(App,self).__init__()
            self.title = 'PyQt4 Video'
            self.left = 100
            self.top = 100
            self.width = 640
            self.height = 480
            self.initUI()

    def initUI(self):
            self.setWindowTitle(self.title)
            self.setGeometry(self.left, self.top, self.width, self.height)
            self.resize(800, 600)
            # create a label
            self.label = QLabel(self)
            self.label.move(0, 0)
            self.label.resize(640, 480)
            th = Thread(self)
            th.changePixmap.connect(lambda p: self.setPixMap(p))
            th.start()

    def setPixMap(self, p):     
        p = QPixmap.fromImage(p)    
        p = p.scaled(640, 480, Qt.KeepAspectRatio)
        self.label.setPixmap(p)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = App()
    ex.show()
    sys.exit(app.exec_())