I successfully setup a virtual environmentusing venv.If i run an opencv application with no multithreading whatsoever, it works fine. However whenever i try to use opencv with multithreading i get the following error:
QObject::moveToThread: Current thread (0x563e422f8180) is not the object's thread (0x563e4262c6d0).
Cannot move to target thread (0x563e422f8180)
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/brighton/PycharmProjects/qc/venv/lib/python3.8/site-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Available platform plugins are: xcb, wayland-org.kde.kwin.qpa, dxcb, xcb, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx.
fish: “python main.py” terminated by signal SIGABRT (Abort)
I am using the code below which i took from a blog to test if opencv is working correctly:
from PyQt5 import QtGui
from PyQt5.QtWidgets import QWidget, QApplication, QLabel, QVBoxLayout
from PyQt5.QtGui import QPixmap
import sys
import cv2
from PyQt5.QtCore import pyqtSignal, pyqtSlot, Qt, QThread
import numpy as np
class VideoThread(QThread):
change_pixmap_signal = pyqtSignal(np.ndarray)
def __init__(self):
super().__init__()
self._run_flag = True
def run(self):
# capture from web cam
cap = cv2.VideoCapture(0)
while self._run_flag:
ret, cv_img = cap.read()
if ret:
self.change_pixmap_signal.emit(cv_img)
# shut down capture system
cap.release()
def stop(self):
"""Sets run flag to False and waits for thread to finish"""
self._run_flag = False
self.wait()
class App(QWidget):
def __init__(self):
super().__init__()
self.setWindowTitle("Qt live label demo")
self.disply_width = 640
self.display_height = 480
# create the label that holds the image
self.image_label = QLabel(self)
self.image_label.resize(self.disply_width, self.display_height)
# create a text label
self.textLabel = QLabel('Webcam')
# create a vertical box layout and add the two labels
vbox = QVBoxLayout()
vbox.addWidget(self.image_label)
vbox.addWidget(self.textLabel)
# set the vbox layout as the widgets layout
self.setLayout(vbox)
# create the video capture thread
self.thread = VideoThread()
# connect its signal to the update_image slot
self.thread.change_pixmap_signal.connect(self.update_image)
# start the thread
self.thread.start()
def closeEvent(self, event):
self.thread.stop()
event.accept()
@pyqtSlot(np.ndarray)
def update_image(self, cv_img):
"""Updates the image_label with a new opencv image"""
qt_img = self.convert_cv_qt(cv_img)
self.image_label.setPixmap(qt_img)
def convert_cv_qt(self, cv_img):
"""Convert from an opencv image to QPixmap"""
rgb_image = cv2.cvtColor(cv_img, cv2.COLOR_BGR2RGB)
h, w, ch = rgb_image.shape
bytes_per_line = ch * w
convert_to_Qt_format = QtGui.QImage(rgb_image.data, w, h, bytes_per_line, QtGui.QImage.Format_RGB888)
p = convert_to_Qt_format.scaled(self.disply_width, self.display_height, Qt.KeepAspectRatio)
return QPixmap.fromImage(p)
if __name__=="__main__":
app = QApplication(sys.argv)
a = App()
a.show()
sys.exit(app.exec_())
but if it was running fine earlier with xorg, that shouldn’t be cause of exception.
