OpenCV and PyQt5 incompatibility workaround

[krishauser]

If you are using the opencv-python library on Linux, there will be a problem with PyQt5. The workaround is as follows:

import cv2
from PyQt5.QtCore import QLibraryInfo
import os

#hack needed to get opencv to work with PyQt5
os.environ["QT_QPA_PLATFORM_PLUGIN_PATH"] = QLibraryInfo.location(QLibraryInfo.PluginsPath)

from klampt import vis
from klampt import WorldModel
import time

w = WorldModel()
w.readFile("../../data/athlete_plane.xml")
vis.add("world",w)
vis.show()
while vis.shown():
    time.sleep(0.1)
vis.kill()

[krishauser]

If you do want to use OpenCV windows, you need to

• show them before the above workaround,
• apply the above workaround after the window is shown
• run the Klampt GUI in single-threaded mode

For example:

import cv2
from PyQt5.QtCore import QLibraryInfo
import os

cap = cv2.VideoCapture(0)
if not cap.isOpened():
    print("Cannot open camera")
    exit()

ret, frame = cap.read()

# if frame is read correctly ret is True
if not ret:
    print("Can't receive frame (stream end?). Exiting ...")
    exit()
# Display the resulting frame
cv2.imshow('frame', frame)

#hack needed to get opencv to work with PyQt5
os.environ["QT_QPA_PLATFORM_PLUGIN_PATH"] = QLibraryInfo.location(QLibraryInfo.PluginsPath)

from klampt import vis
from klampt.vis import GLPluginInterface
from klampt import WorldModel
import time

def capture():
    ret, frame = cap.read()
    
    # if frame is read correctly ret is True
    if not ret:
        print("Can't receive frame (stream end?). Exiting ...")
        vis.show(False)
        return
    # Display the resulting frame
    cv2.imshow('frame', frame)

w = WorldModel()
w.readFile("../../data/athlete_plane.xml")
vis.add("world",w)

#can only run single-threaded mode
vis.loop(callback=capture)

#vis.show()
#while vis.shown():
#    capture()
#    time.sleep(0.01)

vis.kill()

cap.release()