qt能用来打开摄像头的python代码，并注释代码

当然可以！以下是一个使用Qt和OpenCV库来打开摄像头并显示图像的简单代码：

import sys
import cv2
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QImage,QPixmap
from PyQt5.QtWidgets import QApplication,QMainWindow,QMenu,QMenuBar,QAction
from PyQt5.QtWidgets import QFileDialog,QMessageBox,QWidget,QPushButton,QHBoxLayout,QVBoxLayout
from PyQt5.QtGui import QIcon

class App(QMainWindow):
    def __init__(self):
        super().__init__()
        self.left = 10
        self.top = 10
        self.width = 640
        self.height = 480
        self.title = 'PyQt5 Video'
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        self.statusBar().showMessage('Ready')

        menubar = self.menuBar()
        fileMenu = menubar.addMenu('&File')

        openFile = QAction('Open', self)
        openFile.setShortcut('Ctrl+O')
        openFile.setStatusTip('Open video file')
        openFile.triggered.connect(self.file_open)
        fileMenu.addAction(openFile)

        self.label = QLabel(self)
        self.label.setGeometry(0, 0, self.width, self.height)

        startButton = QPushButton('Start Camera', self)
        startButton.clicked.connect(self.start_webcam)
        startButton.setGeometry(10,400,120,30)

        stopButton = QPushButton('Stop Camera', self)
        stopButton.clicked.connect(self.stop_webcam)
        stopButton.setGeometry(140,400,120,30)

        hbox = QHBoxLayout()
        hbox.addWidget(startButton)
        hbox.addWidget(stopButton)
  
        vbox = QVBoxLayout()
        vbox.addWidget(self.label)
        vbox.addLayout(hbox)

        central_widget = QWidget()
        central_widget.setLayout(vbox)
        self.setCentralWidget(central_widget)

        self.show()

    def file_open(self):
        fileName, _ = QFileDialog.getOpenFileName(self,"QFileDialog.getOpenFileName()", "","Video Files (*.mp4 *.flv *.ts *.mts *.avi)")
        if fileName != '':
            self.capture = cv2.VideoCapture(fileName)
            self.capture.set(cv2.CAP_PROP_FRAME_WIDTH, self.width)
            self.capture.set(cv2.CAP_PROP_FRAME_HEIGHT, self.height)

    def start_webcam(self):
        self.capture = cv2.VideoCapture(0)
        self.capture.set(cv2.CAP_PROP_FRAME_WIDTH, self.width)
        self.capture.set(cv2.CAP_PROP_FRAME_HEIGHT, self.height)

        self.timer = QTimer(self)
        self.timer.timeout.connect(self.update_frame)
        self.timer.start(5)

    def update_frame(self):
        ret, self.image = self.capture.read()
        self.image = cv2.cvtColor(self.image, cv2.COLOR_BGR2RGB)
        height, width, channel = self.image.shape
        bytesPerLine = 3 * width
        qImg = QImage(self.image.data, width, height, bytesPerLine, QImage.Format_RGB888)

        self.label.setPixmap(QPixmap.fromImage(qImg))

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

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

这段代码将显示一个窗口，其中包括用于打开并播放视频文件的选项，以及用于开始和停止打开摄像头并显示实时视频的按钮。注释将包括代码中每个功能的解释。注意，在使用此代码之前，您需要安装所需的库。一种简单的方法是打开命令提示符，并使用以下命令:

pip install PyQt5
pip install opencv-python

这将安装所需的库以供使用。