Python PyQt 显示来自 opencv 的视频流

PyQt showing video stream from opencv

提问by Taimur Islam

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.

尝试链接 PyQt 和 Opencv 视频源，无法理解如何将 while 循环应用于连续流视频。它只是拍一张静态照片。请任何人都可以帮助解决问题。

• PtQt=5

• Python=3.6.1

• PtQt=5

• 蟒蛇=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by eyllanesc

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 QThreadclass and send through a signal QImageto update the label. For example:

问题是获取图像的函数只执行一次，并没有更新标签。
正确的做法是把它放在一个循环里面，但是会导致主窗口阻塞。主窗口的阻塞可以通过使用QThread类来解决，并通过发送信号QImage来更新标签。例如：

import cv2
import sys
from PyQt5.QtWidgets import  QWidget, QLabel, QApplication
from PyQt5.QtCore import QThread, Qt, pyqtSignal, pyqtSlot
from PyQt5.QtGui import QImage, QPixmap

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 = QImage(rgbImage.data, w, h, bytesPerLine, 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()
        self.show()

回答by Martin

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

谢谢Taimur Islam 提出这个问题。感谢 eyllanesc 的精彩回答，我对您的代码进行了一些修改。我使用了 PtQt=4 Python=2.7 而我没有使用 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_())

回答by Keno

Updating this for PySide2 and qimage2ndarray

为 PySide2 和 qimage2ndarray 更新这个

from PySide2.QtCore import *
from PySide2.QtGui import *
import cv2 # OpenCV
import qimage2ndarray # for a memory leak,see gist
import sys # for exiting

# Minimal implementation...

def displayFrame():
    ret, frame = cap.read()
    frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
    image = qimage2ndarray.array2qimage(frame)
    label.setPixmap(QPixmap.fromImage(image))

app = QApplication([])
window = QWidget()

# OPENCV

cap = cv2.VideoCapture(0)
cap.set(cv2.CAP_PROP_FRAME_WIDTH, 320)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 240)

# timer for getting frames

timer = QTimer()
timer.timeout.connect(displayFrame)
timer.start(60)
label = QLabel('No Camera Feed')
button = QPushButton("Quiter")
button.clicked.connect(sys.exit) # quiter button 
layout = QVBoxLayout()
layout.addWidget(button)
layout.addWidget(label)
window.setLayout(layout)
window.show()
app.exec_()

# See also: https://gist.github.com/bsdnoobz/8464000