How to fix the error "QObject::moveToThread:" in opencv in python?
Question:
I am using opencv2 in python with the code
import cv2
cv2.namedWindow("output", cv2.WINDOW_NORMAL)
cv2.imshow("output",im)
cv2.resizeWindow('output', 400,400)
cv2.waitKey(0)
cv2.destroyAllWindows()
I have the error as
QObject::moveToThread: Current thread (0x1d2c9cf0) is not the object's thread (0x1d347b20).
Cannot move to target thread (0x1d2c9cf0)
I debug and found that it happened when I use cv2.waitKey(0)
. How should I fix it? Thanks
Update: I am using 3.3.0.0. If I use older version, I have error
OpenCV Error: Unspecified error (The function is not implemented. Rebuild the library with Windows, GTK+ 2.x or Carbon support. If you are on Ubuntu or Debian, install libgtk2.0-dev and pkg-config, then re-run cmake or configure script) in cvDestroyAllWindows, file /io/opencv/modules/highgui/src/window.cpp, line 577
Traceback (most recent call last):
File "tools/demo_handbone.py", line 220, in <module>
demo(net, im_name)
File "tools/demo_handbone.py", line 159, in demo
cv2.destroyAllWindows()
cv2.error: /io/opencv/modules/highgui/src/window.cpp:577: error: (-2) The function is not implemented. Rebuild the library with Windows, GTK+ 2.x or Carbon support. If you are on Ubuntu or Debian, install libgtk2.0-dev and pkg-config, then re-run cmake or configure script in function cvDestroyAllWindows
Answers:
First of all, uninstall any versions of OpenCV you may have installed. If you installed using pip
:
sudo pip uninstall opencv-python
Next, try installing OpenCV using your Linux distro’s package manager. For Ubuntu/Debian, this is:
sudo apt install libopencv-dev python3-opencv
I tried the above mentioned method and could get opencv module working for my project which uses python3.x interpreter.
After performing few experiments, i got it working by doing the below steps:
1) Install opencv-python in your machine using:
sudo pip3 install opencv-python
2) On the python3.x terminal find the version:
>>> import cv2
>>> cv2.__version__
'3.4.1'
3) Get the same version of OpenCV from their official page.
4) Perform the CMake settings as mentioned in opencv tutorial.
Note the location specified in PYTHON3_PACKAGES_PATH
5) Once build has been performed, got to the install location specified in PYTHON3_PACKAGES_PATH. Move the library named cv2.cpython-*-gnu.so to the current python3.x dist-packages path:
usr/local/lib/python3.5/dist-packages/cv2
6) Reload your python3 project and try again!
This problem not present if runing opencv without virtualenviroment.
My system:
Kbuntu 18.04 LTS
GTX 1050
CUDA 9.2
Tensorflow 1.9
The answer of @Mateen works great if you have Ubuntu version 17 and above. For Ubuntu 16, it’s better to compile from sources your opencv python. As @Varun mentioned, follow the opencv tutorial. However, to successfully compile opencv with python 3 I have to add some flags in cmake command:
cmake -DCMAKE_BUILD_TYPE=RELEASE -DPYTHON_DEFAULT_EXECUTABLE=$(which python3) -DPYTHON_INCLUDE_DIR2=/usr/include/x86_64-linux-gnu/python3.5m/ -DPYTHON3_NUMPY_INCLUDE_DIRS=/usr/local/lib/python3.5/dist-packages/numpy/core/include/ ..
Hope that will be helpful.
I fixed this under Ubuntu 18.04 LTS by uninstalling any OpenCV packages from pip
and apt
and installing OpenCV directly from source. Maybe this tutorial will help:
https://www.pyimagesearch.com/2018/08/15/how-to-install-opencv-4-on-ubuntu/
I don’t know why, but installation of matplotlib solved for me the problem with the error
QObject::moveToThread: Current thread (0x1d2c9cf0) is not the object's thread (0x1d347b20).
Cannot move to target thread (0x1d2c9cf0)
I emphasize that I prepared fresh conda environment where matplotlib was installed. Opencv was installed by pip in conda env as follow pip install opencv-python opencv-contrib-python
.
The openCv author says that this problem comes from different Qt versions in openCv and the linux distro. That is: openCv comes with Qt4, but Qt5 is already installed.
I followed the solution suggested by @Varun and it worked for me (using Python 3).
However, I didn’t install the built files, as I do not have the admin rights on the system where I need the cv package. A cmake
, followed by make
was enough, I then took the cv2.*.gnu
file from ../build/lib/python3
folder and replaced the one in the site-packages/cv2
folder of my virtual environment
I was able to fix this problem by installing new pyqt.
if you are using anaconda, just write down below:
$ conda install pyqt
I solved this issue and I posted my solution in related issue on OpenCV github page. But for your convenience, I will post it here also.
In my case, I did almost all the solutions:
- installing using pip3 install opencv-python
- installing using apt install python-opencv
- I followed @areche solution, I end up with
kdelibs5-plugins
which was an important module for most of my desktop environments, so I give up on uninstalling it.
Finally, I found a solution for my case
pip uninstall opencv-python
on all instances of my python and virtual environments
pip3 uninstall opencv-python
on all instances of my python and virtual environments
sudo apt remove python-opencv
then I downloaded the most recent opencv, in my case opencv-4.1.1
, I build it.
for building :
mkdir build; cd build; ccmake ..
then I pressed pressed c
, again pressed c
, then pressed g
to generate make files, then
sudo make -j8
after successful building, I copied buildlibpython3cv2.cpython.xxxxxx.so
to usr/local/lib/python3.5/dist-packages/
and renamed it to cv2.so
Do the same for each virtualenv that you have. ( I’m not sure if it is logical, but it worked for me).
then everything worked fine without any error.
This may be caused by conflicting installations of Qt libraries. The following command fixed it for me:
sudo apt-get remove libqt5x11extras5 libqt5x11extras5-dev
I had the same problem. Using opencv imshow function raised the moving thread error. Eventually, I found that Ubuntu 16.04 has a preinstalled pyqt5 while OpenCV needs pqty4.
Therefore, this may be caused by conflicting installations of Qt libraries. The following command fixed it for me:
sudo apt-get remove libqt5x11extras5 libqt5x11extras5-dev
I had the same problem when i tried to run a detectron2 demo. My OS is Centos7 and i
uninstall some applications about qt.
find applications about qt.
yum list installed |grep qt
remove applications
yum -y remove xxx...
I know the thread is a bit old but posting for anyone else out there, I faced the same problem and it was because even after running
pip3 uninstall opencv-python
there was another version of open-cv in my system which I checked by
pip list
(I’m guessing that pip only removes the first version it finds)
So I ran this command again
pip3 uninstall opencv-python
And now simply installing opencv by
pip install opencv-python
worked for me.
I got same problem, it was from opencv-python
version problem for me.
My Linux machine’s environment is as following:
$ cat /etc/lsb-release
...
DISTRIB_DESCRIPTION="Ubuntu 18.04.5 LTS"
$ date
Tue Aug 11 11:43:16 KST 2020
$ python --version
Python 3.7.8
$ pip list|grep Qt
PyQt5 5.15.0
PyQt5-sip 12.8.0
$ pip list|grep opencv-python
opencv-python 4.3.0.38
I downgraded opencv-python 4.3.0.38 to 4.3.0.36.
$ pip uninstall opencv-python
$ pip install opencv-python==4.3.0.36
$ pip list|grep opencv-python
opencv-python 4.3.0.36
This error occurs in higher versions of openCv like 4.3.0.38 or higher, i tried 4.3.0.36 version with pip and this problem solved for me, but in lower version i were facing lots of problems, like window not loading correctly,If are using Ubuntu i would recommend you to uninstall opencv from your system completely and try to reinstall with command given below,
pip install opencv-contrib-python3
This can happen if you are using an Anaconda virtual environment and did both conda install pyqt
(1) and pip install opencv-python
. This creates a conflict between the two PyQt versions (opencv-python
ships with its own) and causes the errors.
The solution is to install PyQt via pip
, i.e. pip install PyQt5
.
(1) Or anything that depends on pyqt
, e.g. conda install matplotlib
.
refer to: https://blog.csdn.net/flyfor2013/article/details/110132458
pip3 uninstall opencv-python
pip3 install opencv-python==4.1.1.26
when I downgrade opencv-python 4.5 -> 4.1.1.26 then Ok
pip3 >= 20.3 use: pip3 install --use-deprecated=legacy-resolver opencv-python==
pip3 >= 9.0 use: pip3 install opencv-python==
and I try
pip3 uninstall opencv-python
pip3 install opencv-python==4.3.0.36
Ok, too
It is the compatibility issue. Even the way of "conda install install pyqt" does work. Please make sure that you can install the opencv libraries with the specific versions. Higher versions may incur the same issues.
pip install opencv-python==4.1.1.26
pip install opencv-contrib-python==4.1.1.26
Cheers,
The issue is with OpenCV version, The following version solved all issues for me.
pip uninstall opencv-python
pip install opencv-python==4.1.2.30
I am using – Python 3.8.5 with conda
I tried with upgrading pyqt too but it didn’t work
Just reinstall opencv-python lib, it’s OK.
pip uninstall opencv-python
pip install opencv-python=4.2.0.34
The version 4.2 is the latest opencv python that don’t throw this error. I tried 4.3 or 4.4 +, it’s don’t work.
The main reason of this question may be the confliction between PyQt5 and Opencv.
I had the same problem and I did not find any solution. By trial and error, I found that my OpenCV
version is corrupted. As a result, I deleted it and install a new fresh one. You can use one of these two options:
1. Terminal
run brew uninstall opencv3
to uninstall opencv
then install it using sudo apt-get install libopencv-dev python-opencv
command.
2. Anaconda
Actually, I used this method for my own problem.
This problem is due to the conflict between opencv-python’s own Qt5 and the one used by other packages. In my case, matplotlib
is installed via conda
, then pyqt
is also installed as a matplotlib
‘s dependency. My solution is as follows:
- Uninstall
matplotlib
: conda remove matplotlib
- Install
opencv-python
and matplotlib
: pip install matplotlib opencv-python
Now, matplotlib
installed via pip
doesn’t require pyqt
and the conflict is solved.
Note: The latest version 4.5.4.x gets error with python 3.9
, consider using lower version such as 4.5.1.x in this case.
In case you are using matplotlib, see this answer: https://stackoverflow.com/a/49887744/13268880
TL;DR: matplotlib.use('Agg')
In my application I wanted to use PyQt without any of opencv’s GUI functionality, so the solution was to remove my current vertion of opencv-python, then instead pip install opencv-python-headless
(or opencv-contrib-python-headless
if you prefer). That way, opencv would be installed without its conflicting Qt library.
See: https://github.com/opencv/opencv-python#installation-and-usage
Downgrade the python version from 3.9.13 to 3.8.10
conda install python=3.8.10
pip install opencv-python==4.5.2.54
worked for me.
My system environment: Ubuntu 20.04 Anaconda 3.8
I was used matplotlib to display images and face this problem.
pip install opencv-python-headless
not work for me.
pip uninstall pyqt5
then pip install pyqt5==5.12
and it works well.
pip uninstall PyQt5 works for me.
seems like a conflict between PyQt5 and opencv-python.
I am using opencv2 in python with the code
import cv2
cv2.namedWindow("output", cv2.WINDOW_NORMAL)
cv2.imshow("output",im)
cv2.resizeWindow('output', 400,400)
cv2.waitKey(0)
cv2.destroyAllWindows()
I have the error as
QObject::moveToThread: Current thread (0x1d2c9cf0) is not the object's thread (0x1d347b20).
Cannot move to target thread (0x1d2c9cf0)
I debug and found that it happened when I use cv2.waitKey(0)
. How should I fix it? Thanks
Update: I am using 3.3.0.0. If I use older version, I have error
OpenCV Error: Unspecified error (The function is not implemented. Rebuild the library with Windows, GTK+ 2.x or Carbon support. If you are on Ubuntu or Debian, install libgtk2.0-dev and pkg-config, then re-run cmake or configure script) in cvDestroyAllWindows, file /io/opencv/modules/highgui/src/window.cpp, line 577
Traceback (most recent call last):
File "tools/demo_handbone.py", line 220, in <module>
demo(net, im_name)
File "tools/demo_handbone.py", line 159, in demo
cv2.destroyAllWindows()
cv2.error: /io/opencv/modules/highgui/src/window.cpp:577: error: (-2) The function is not implemented. Rebuild the library with Windows, GTK+ 2.x or Carbon support. If you are on Ubuntu or Debian, install libgtk2.0-dev and pkg-config, then re-run cmake or configure script in function cvDestroyAllWindows
First of all, uninstall any versions of OpenCV you may have installed. If you installed using pip
:
sudo pip uninstall opencv-python
Next, try installing OpenCV using your Linux distro’s package manager. For Ubuntu/Debian, this is:
sudo apt install libopencv-dev python3-opencv
I tried the above mentioned method and could get opencv module working for my project which uses python3.x interpreter.
After performing few experiments, i got it working by doing the below steps:
1) Install opencv-python in your machine using:
sudo pip3 install opencv-python
2) On the python3.x terminal find the version:
>>> import cv2
>>> cv2.__version__
'3.4.1'
3) Get the same version of OpenCV from their official page.
4) Perform the CMake settings as mentioned in opencv tutorial.
Note the location specified in PYTHON3_PACKAGES_PATH
5) Once build has been performed, got to the install location specified in PYTHON3_PACKAGES_PATH. Move the library named cv2.cpython-*-gnu.so to the current python3.x dist-packages path:
usr/local/lib/python3.5/dist-packages/cv2
6) Reload your python3 project and try again!
This problem not present if runing opencv without virtualenviroment.
My system:
Kbuntu 18.04 LTS
GTX 1050
CUDA 9.2
Tensorflow 1.9
The answer of @Mateen works great if you have Ubuntu version 17 and above. For Ubuntu 16, it’s better to compile from sources your opencv python. As @Varun mentioned, follow the opencv tutorial. However, to successfully compile opencv with python 3 I have to add some flags in cmake command:
cmake -DCMAKE_BUILD_TYPE=RELEASE -DPYTHON_DEFAULT_EXECUTABLE=$(which python3) -DPYTHON_INCLUDE_DIR2=/usr/include/x86_64-linux-gnu/python3.5m/ -DPYTHON3_NUMPY_INCLUDE_DIRS=/usr/local/lib/python3.5/dist-packages/numpy/core/include/ ..
Hope that will be helpful.
I fixed this under Ubuntu 18.04 LTS by uninstalling any OpenCV packages from pip
and apt
and installing OpenCV directly from source. Maybe this tutorial will help:
https://www.pyimagesearch.com/2018/08/15/how-to-install-opencv-4-on-ubuntu/
I don’t know why, but installation of matplotlib solved for me the problem with the error
QObject::moveToThread: Current thread (0x1d2c9cf0) is not the object's thread (0x1d347b20).
Cannot move to target thread (0x1d2c9cf0)
I emphasize that I prepared fresh conda environment where matplotlib was installed. Opencv was installed by pip in conda env as follow pip install opencv-python opencv-contrib-python
.
The openCv author says that this problem comes from different Qt versions in openCv and the linux distro. That is: openCv comes with Qt4, but Qt5 is already installed.
I followed the solution suggested by @Varun and it worked for me (using Python 3).
However, I didn’t install the built files, as I do not have the admin rights on the system where I need the cv package. A cmake
, followed by make
was enough, I then took the cv2.*.gnu
file from ../build/lib/python3
folder and replaced the one in the site-packages/cv2
folder of my virtual environment
I was able to fix this problem by installing new pyqt.
if you are using anaconda, just write down below:
$ conda install pyqt
I solved this issue and I posted my solution in related issue on OpenCV github page. But for your convenience, I will post it here also.
In my case, I did almost all the solutions:
- installing using pip3 install opencv-python
- installing using apt install python-opencv
- I followed @areche solution, I end up with
kdelibs5-plugins
which was an important module for most of my desktop environments, so I give up on uninstalling it.
Finally, I found a solution for my case
pip uninstall opencv-python
on all instances of my python and virtual environmentspip3 uninstall opencv-python
on all instances of my python and virtual environmentssudo apt remove python-opencv
then I downloaded the most recent opencv, in my case opencv-4.1.1
, I build it.
for building :
mkdir build; cd build; ccmake ..
then I pressed pressed c
, again pressed c
, then pressed g
to generate make files, then
sudo make -j8
after successful building, I copied buildlibpython3cv2.cpython.xxxxxx.so
to usr/local/lib/python3.5/dist-packages/
and renamed it to cv2.so
Do the same for each virtualenv that you have. ( I’m not sure if it is logical, but it worked for me).
then everything worked fine without any error.
This may be caused by conflicting installations of Qt libraries. The following command fixed it for me:
sudo apt-get remove libqt5x11extras5 libqt5x11extras5-dev
I had the same problem. Using opencv imshow function raised the moving thread error. Eventually, I found that Ubuntu 16.04 has a preinstalled pyqt5 while OpenCV needs pqty4.
Therefore, this may be caused by conflicting installations of Qt libraries. The following command fixed it for me:
sudo apt-get remove libqt5x11extras5 libqt5x11extras5-dev
I had the same problem when i tried to run a detectron2 demo. My OS is Centos7 and i
uninstall some applications about qt.
find applications about qt.
yum list installed |grep qt
remove applications
yum -y remove xxx...
I know the thread is a bit old but posting for anyone else out there, I faced the same problem and it was because even after running
pip3 uninstall opencv-python
there was another version of open-cv in my system which I checked by
pip list
(I’m guessing that pip only removes the first version it finds)
So I ran this command again
pip3 uninstall opencv-python
And now simply installing opencv by
pip install opencv-python
worked for me.
I got same problem, it was from opencv-python
version problem for me.
My Linux machine’s environment is as following:
$ cat /etc/lsb-release
...
DISTRIB_DESCRIPTION="Ubuntu 18.04.5 LTS"
$ date
Tue Aug 11 11:43:16 KST 2020
$ python --version
Python 3.7.8
$ pip list|grep Qt
PyQt5 5.15.0
PyQt5-sip 12.8.0
$ pip list|grep opencv-python
opencv-python 4.3.0.38
I downgraded opencv-python 4.3.0.38 to 4.3.0.36.
$ pip uninstall opencv-python
$ pip install opencv-python==4.3.0.36
$ pip list|grep opencv-python
opencv-python 4.3.0.36
This error occurs in higher versions of openCv like 4.3.0.38 or higher, i tried 4.3.0.36 version with pip and this problem solved for me, but in lower version i were facing lots of problems, like window not loading correctly,If are using Ubuntu i would recommend you to uninstall opencv from your system completely and try to reinstall with command given below,
pip install opencv-contrib-python3
This can happen if you are using an Anaconda virtual environment and did both conda install pyqt
(1) and pip install opencv-python
. This creates a conflict between the two PyQt versions (opencv-python
ships with its own) and causes the errors.
The solution is to install PyQt via pip
, i.e. pip install PyQt5
.
(1) Or anything that depends on pyqt
, e.g. conda install matplotlib
.
refer to: https://blog.csdn.net/flyfor2013/article/details/110132458
pip3 uninstall opencv-python
pip3 install opencv-python==4.1.1.26
when I downgrade opencv-python 4.5 -> 4.1.1.26 then Ok
pip3 >= 20.3 use: pip3 install --use-deprecated=legacy-resolver opencv-python==
pip3 >= 9.0 use: pip3 install opencv-python==
and I try
pip3 uninstall opencv-python
pip3 install opencv-python==4.3.0.36
Ok, too
It is the compatibility issue. Even the way of "conda install install pyqt" does work. Please make sure that you can install the opencv libraries with the specific versions. Higher versions may incur the same issues.
pip install opencv-python==4.1.1.26
pip install opencv-contrib-python==4.1.1.26
Cheers,
The issue is with OpenCV version, The following version solved all issues for me.
pip uninstall opencv-python
pip install opencv-python==4.1.2.30
I am using – Python 3.8.5 with conda
I tried with upgrading pyqt too but it didn’t work
Just reinstall opencv-python lib, it’s OK.
pip uninstall opencv-python
pip install opencv-python=4.2.0.34
The version 4.2 is the latest opencv python that don’t throw this error. I tried 4.3 or 4.4 +, it’s don’t work.
The main reason of this question may be the confliction between PyQt5 and Opencv.
I had the same problem and I did not find any solution. By trial and error, I found that my OpenCV
version is corrupted. As a result, I deleted it and install a new fresh one. You can use one of these two options:
1. Terminal
run brew uninstall opencv3
to uninstall opencv
then install it using sudo apt-get install libopencv-dev python-opencv
command.
2. Anaconda
Actually, I used this method for my own problem.
This problem is due to the conflict between opencv-python’s own Qt5 and the one used by other packages. In my case, matplotlib
is installed via conda
, then pyqt
is also installed as a matplotlib
‘s dependency. My solution is as follows:
- Uninstall
matplotlib
:conda remove matplotlib
- Install
opencv-python
andmatplotlib
:pip install matplotlib opencv-python
Now, matplotlib
installed via pip
doesn’t require pyqt
and the conflict is solved.
Note: The latest version 4.5.4.x gets error with python 3.9
, consider using lower version such as 4.5.1.x in this case.
In case you are using matplotlib, see this answer: https://stackoverflow.com/a/49887744/13268880
TL;DR: matplotlib.use('Agg')
In my application I wanted to use PyQt without any of opencv’s GUI functionality, so the solution was to remove my current vertion of opencv-python, then instead pip install opencv-python-headless
(or opencv-contrib-python-headless
if you prefer). That way, opencv would be installed without its conflicting Qt library.
See: https://github.com/opencv/opencv-python#installation-and-usage
Downgrade the python version from 3.9.13 to 3.8.10
conda install python=3.8.10
pip install opencv-python==4.5.2.54
worked for me.
My system environment: Ubuntu 20.04 Anaconda 3.8
I was used matplotlib to display images and face this problem.
pip install opencv-python-headless
not work for me.
pip uninstall pyqt5
then pip install pyqt5==5.12
and it works well.
pip uninstall PyQt5 works for me.
seems like a conflict between PyQt5 and opencv-python.