Displaying webcam feed using OpenCV and Python+PySide.

read-camera.py

#!/usr/bin/env python

from PySide.QtCore import *
from PySide.QtGui import *
import cv2
import sys

class MainApp(QWidget):

    def __init__(self):
        QWidget.__init__(self)
        self.video_size = QSize(320, 240)
        self.setup_ui()
        self.setup_camera()

    def setup_ui(self):
        """Initialize widgets.
        """
        self.image_label = QLabel()
        self.image_label.setFixedSize(self.video_size)

        self.quit_button = QPushButton("Quit")
        self.quit_button.clicked.connect(self.close)

        self.main_layout = QVBoxLayout()
        self.main_layout.addWidget(self.image_label)
        self.main_layout.addWidget(self.quit_button)

        self.setLayout(self.main_layout)

    def setup_camera(self):
        """Initialize camera.
        """
        self.capture = cv2.VideoCapture(0)
        self.capture.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH, self.video_size.width())
        self.capture.set(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT, self.video_size.height())

        self.timer = QTimer()
        self.timer.timeout.connect(self.display_video_stream)
        self.timer.start(30)

    def display_video_stream(self):
        """Read frame from camera and repaint QLabel widget.
        """
        _, frame = self.capture.read()
        frame = cv2.cvtColor(frame, cv2.cv.CV_BGR2RGB)
        frame = cv2.flip(frame, 1)
        image = QImage(frame, frame.shape[1], frame.shape[0], 
                       frame.strides[0], QImage.Format_RGB888)
        self.image_label.setPixmap(QPixmap.fromImage(image))

if __name__ == "__main__":
    app = QApplication(sys.argv)
    win = MainApp()
    win.show()
    sys.exit(app.exec_())

There is a huge memory leak when I run this code, I have changed the streaming resolution to 1920x1080. If the self.timer.start(30) is changed to 250 milliseconds, the memory leak is slower but still present. Any way to stop the mem leak?

 import qimage2ndarray
def display_video_stream(self):
    """Read frame from camera and repaint QLabel widget.
    """
    _, frame = self.capture.read()
    frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
    frame = cv2.flip(frame, 1)
    image = qimage2ndarray.array2qimage(frame)  #SOLUTION FOR MEMORY LEAK
    self.image_label.setPixmap(QPixmap.fromImage(image))

thanks for the solution ragu25

Thanks for the example!
I don't see a memory leak using PySide6.

For PySide6:

from PySide6.QtCore import *
from PySide6.QtGui import *
from PySide6.QtWidgets import *
import cv2
import sys
...

requirements.txt (install via pip install -r "requirements.txt"):

pyside6==6.1.2
opencv-python==4.5.2.52

It needed some editing to work with
pyside2 5.15.2
opencv-python 4.3.0.36
Here is updated version:

#!/usr/bin/env python

from PySide2.QtCore import *
from PySide2.QtGui import *
from PySide2.QtWidgets import *
import qimage2ndarray

import cv2
import sys

class MainApp(QWidget):

    def __init__(self):
        QWidget.__init__(self)
        self.video_size = QSize(320, 240)
        self.setup_ui()
        self.setup_camera()

    def setup_ui(self):
        """Initialize widgets.
        """
        self.image_label = QLabel()
        self.image_label.setFixedSize(self.video_size)

        self.quit_button = QPushButton("Quit")
        self.quit_button.clicked.connect(self.close)

        self.main_layout = QVBoxLayout()
        self.main_layout.addWidget(self.image_label)
        self.main_layout.addWidget(self.quit_button)

        self.setLayout(self.main_layout)

    def setup_camera(self):
        """Initialize camera.
        """
        self.capture = cv2.VideoCapture(0)
        self.capture.set(cv2.CAP_PROP_FRAME_WIDTH, self.video_size.width())
        self.capture.set(cv2.CAP_PROP_FRAME_HEIGHT, self.video_size.height())

        self.timer = QTimer()
        self.timer.timeout.connect(self.display_video_stream)
        self.timer.start(30)

    def display_video_stream(self):
        """Read frame from camera and repaint QLabel widget.
        """
        _, frame = self.capture.read()
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        frame = cv2.flip(frame, 1)
        image = qimage2ndarray.array2qimage(frame)  #SOLUTION FOR MEMORY LEAK
        self.image_label.setPixmap(QPixmap.fromImage(image))

if __name__ == "__main__":
    app = QApplication(sys.argv)
    win = MainApp()
    win.show()
    sys.exit(app.exec_())

Hey there,

Is it OK to use and modify the code for a dissertation I'm working on?

sure, i have no issues and not responsible for any issues that it might cause