# \#qt **URL:** https://forum.opencv.org/tag/qt/172.md [Latest](https://forum.opencv.org/latest.md) · [Categories](https://forum.opencv.org/categories.md) · [Tags](https://forum.opencv.org/tags.md) --- ## [Unclear and unstable meaning of VideoCapture camera index on Windows (MSMF) when multiple cameras are present](https://forum.opencv.org/t/unclear-and-unstable-meaning-of-videocapture-camera-index-on-windows-msmf-when-multiple-cameras-are-present/24262)
**Author:** [@Mq-b](https://forum.opencv.org/u/Mq-b)\ **Replies:** 0\ **Last updated:** [December 18, 2025, 6:31am UTC](https://forum.opencv.org/t/unclear-and-unstable-meaning-of-videocapture-camera-index-on-windows-msmf-when-multiple-cameras-are-present/24262 "2025-12-18T06:31:06Z")
Environment OS: Windows 11 Compiler: MSVC (Visual Studio 2022) OpenCV version: (please fill in, e.g. 4.9.0) Backend: MSMF Related framework: Qt (QCameraInfo) Description I am experiencing serious ambigu… --- ## [Using QT on macos 15.5 with opencv (and the unexpected problems)](https://forum.opencv.org/t/using-qt-on-macos-15-5-with-opencv-and-the-unexpected-problems/21089)
**Author:** [@Jason\_Stelzer](https://forum.opencv.org/u/Jason_Stelzer)\ **Replies:** 0\ **Last updated:** [May 24, 2025, 11:39pm UTC](https://forum.opencv.org/t/using-qt-on-macos-15-5-with-opencv-and-the-unexpected-problems/21089 "2025-05-24T23:39:19Z")
Hey, I have an app I wrote in rust on linux that I wanted to use on my mac. The porting effort was minimal, but the version of opencv I got via brew wasn’t linked to qt. On the linux side, I have a hot key that shows he… --- ## [OpenCV imshow Error: QSocketNotifier: Can only be used with threads started with QThread (No Qt Usage)](https://forum.opencv.org/t/opencv-imshow-error-qsocketnotifier-can-only-be-used-with-threads-started-with-qthread-no-qt-usage/21064)
**Author:** [@fdl](https://forum.opencv.org/u/fdl)\ **Replies:** 1\ **Last updated:** [May 23, 2025, 8:31am UTC](https://forum.opencv.org/t/opencv-imshow-error-qsocketnotifier-can-only-be-used-with-threads-started-with-qthread-no-qt-usage/21064 "2025-05-23T08:31:58Z")
When calling cv::imshow to display an image, the program throws the error: QSocketNotifier: Can only be used with threads started with QThread. I confirm that my code does not directly use the Qt library (no Qt headers… --- ## [Build opencv\_cvv and opencv\_world failed](https://forum.opencv.org/t/build-opencv-cvv-and-opencv-world-failed/20534)
**Author:** [@WWjh](https://forum.opencv.org/u/WWjh)\ **Replies:** 4\ **Last updated:** [March 17, 2025, 1:53am UTC](https://forum.opencv.org/t/build-opencv-cvv-and-opencv-world-failed/20534 "2025-03-17T01:53:06Z")
my version is opencv-4.9.0,so is the opencv\_contrib;build in VS2022，Qt version is 5.14.0; It will build failed when I both check “Build\_opencv\_world” and “Build\_opencv\_cvv”。the compiler give link errors inthe picture; … --- ## [OpenCV Install Failure for Qt6.7.2 (procedure entry point could not be found in the dynamic link library)](https://forum.opencv.org/t/opencv-install-failure-for-qt6-7-2-procedure-entry-point-could-not-be-found-in-the-dynamic-link-library/20386)
**Author:** [@Yusuke](https://forum.opencv.org/u/Yusuke)\ **Replies:** 1\ **Last updated:** [March 10, 2025, 9:47am UTC](https://forum.opencv.org/t/opencv-install-failure-for-qt6-7-2-procedure-entry-point-could-not-be-found-in-the-dynamic-link-library/20386 "2025-03-10T09:47:53Z")
I have been struggling for a week to install OpenCV in a Qt environment without success. Please let me know if you discover any potential solutions. Environment Windows11 64bit Qt 6.7.3 Qt Creator 15.0.0 Cmake 3.26.4 O… --- ## [Does OpenCV 4.11.0 have QT support?](https://forum.opencv.org/t/does-opencv-4-11-0-have-qt-support/20405)
**Author:** [@Devin\_11](https://forum.opencv.org/u/Devin_11)\ **Replies:** 3\ **Last updated:** [March 5, 2025, 10:58am UTC](https://forum.opencv.org/t/does-opencv-4-11-0-have-qt-support/20405 "2025-03-05T10:58:18Z")
I am trying to build a C++ OpenCV application with CMake, I checked the options for the OpenCV config but can not find the WITH\_QT option, so i am confused if I can build a OpenCV 4.11.0 application with Qt GUI interface… --- ## [Opencv webassembly](https://forum.opencv.org/t/opencv-webassembly/19843)
**Author:** [@bcatherine](https://forum.opencv.org/u/bcatherine)\ **Replies:** 2\ **Last updated:** [January 22, 2025, 8:32pm UTC](https://forum.opencv.org/t/opencv-webassembly/19843 "2025-01-22T20:32:29Z")
debian 12 qt 6.7.1 Emscripten 3.50 opencv 4.6.0 I have a QT project that plays a video in a QT interface and puts it in a label. In desktop compilation everything works normally, but in web assembly compilation an er… --- ## [Opencv build issue with PyQt6](https://forum.opencv.org/t/opencv-build-issue-with-pyqt6/19702)
**Author:** [@Alan\_Miller](https://forum.opencv.org/u/Alan_Miller)\ **Replies:** 0\ **Last updated:** [January 6, 2025, 11:55pm UTC](https://forum.opencv.org/t/opencv-build-issue-with-pyqt6/19702 "2025-01-06T23:55:41Z")
I’m trying to build OpenCV 4 with QT 6.8.1 and OpenVino. First I built Qt 6.8.1 and OpenVino locally \> qmake --version QMake version 3.1 Using Qt version 6.8.1 in /opt/qt/6.8.1/lib \> cat /opt/intel/openvino\_2024.6.0/… --- ## [Undefined reference to \`cv::imread' with Qt and MinGW](https://forum.opencv.org/t/undefined-reference-to-cv-imread-with-qt-and-mingw/19415)
**Author:** [@Dani](https://forum.opencv.org/u/Dani)\ **Replies:** 1\ **Last updated:** [December 2, 2024, 9:06am UTC](https://forum.opencv.org/t/undefined-reference-to-cv-imread-with-qt-and-mingw/19415 "2024-12-02T09:06:41Z")
Hi, I am quite new to QT and OpenCV. I am using QT version 6.8 and OpenCV 4.10. I have found a channel in youtube from Qt With Ketan. I follow the steps of the first video: https://www.youtube.com/watch?v=yVeXXuGnnxs&l… --- ## [Opencv4.5.2 build error :OpenCVCompilerOptimizations.cmake:593: error: Compiler doesn't support baseline optimization flags: cmake/OpenCVCompilerOptions.cmake:311 (ocv\_compiler\_optimization\_options) CMakeLists.txt:617 (include)](https://forum.opencv.org/t/opencv4-5-2-build-error-opencvcompileroptimizations-cmake-error-compiler-doesnt-support-baseline-optimization-flags-cmake-opencvcompileroptions-cmake-311-ocv-compiler-optimization-options-cmakelists-txt-617-include/18865)
**Author:** [@joe\_hanmy](https://forum.opencv.org/u/joe_hanmy)\ **Replies:** 6\ **Last updated:** [September 30, 2024, 11:41am UTC](https://forum.opencv.org/t/opencv4-5-2-build-error-opencvcompileroptimizations-cmake-error-compiler-doesnt-support-baseline-optimization-flags-cmake-opencvcompileroptions-cmake-311-ocv-compiler-optimization-options-cmakelists-txt-617-include/18865 "2024-09-30T11:41:17Z")
The compiler is Desktop\_Qt\_5\_14\_2\_MinGW\_64\_bit-Release. Can I disbale those lines: if(NOT HAVE\_CPU\_BASELINE\_FLAGS) message(FATAL\_ERROR “Compiler doesn’t support baseline optimization flags: ${CPU\_BASELINE\_FLAGS}”) e… --- ## [Is it possible to save big images without blocking Qt GUI?](https://forum.opencv.org/t/is-it-possible-to-save-big-images-without-blocking-qt-gui/18369)
**Author:** [@SinPool](https://forum.opencv.org/u/SinPool)\ **Replies:** 6\ **Last updated:** [July 31, 2024, 8:57am UTC](https://forum.opencv.org/t/is-it-possible-to-save-big-images-without-blocking-qt-gui/18369 "2024-07-31T08:57:20Z")
I have a gui in pyqt and need to save a big image, when I try to use opencv imwrite it blocks application gui and makes it not responding, I tried to put imwrite in another thread but it didn’t do anything, is there any … --- ## [OpenCV on VS2022 and Qt, no console output except for parallel backend INFO](https://forum.opencv.org/t/opencv-on-vs2022-and-qt-no-console-output-except-for-parallel-backend-info/18181)
**Author:** [@ban](https://forum.opencv.org/u/ban)\ **Replies:** 1\ **Last updated:** [July 6, 2024, 10:35am UTC](https://forum.opencv.org/t/opencv-on-vs2022-and-qt-no-console-output-except-for-parallel-backend-info/18181 "2024-07-06T10:35:25Z")
I encountered the following issue while developing with OpenCV on VS2022 and Qt 6.8 platforms: After completing the program, there were no compilation errors, and the program ran without any errors reported. However, th… --- ## [QObject::killTimer: Timers cannot be stopped from another thread (when using waitKey function)](https://forum.opencv.org/t/qobject-timers-cannot-be-stopped-from-another-thread-when-using-waitkey-function/17903)
**Author:** [@alexek](https://forum.opencv.org/u/alexek)\ **Replies:** 2\ **Last updated:** [June 26, 2024, 2:05pm UTC](https://forum.opencv.org/t/qobject-timers-cannot-be-stopped-from-another-thread-when-using-waitkey-function/17903 "2024-06-26T14:05:50Z")
Hi, all! I’m using 2 threads in my code (both started from main thread which sleeps and waits till the 2 threds will finish), one decodes frames, the other blits them to a window. In the thread that blits, I use the fol… --- ## [Cv::imshow opens a window with a strange UI interface](https://forum.opencv.org/t/cv-imshow-opens-a-window-with-a-strange-ui-interface/17778)
**Author:** [@JJRJ](https://forum.opencv.org/u/JJRJ)\ **Replies:** 2\ **Last updated:** [May 30, 2024, 12:57pm UTC](https://forum.opencv.org/t/cv-imshow-opens-a-window-with-a-strange-ui-interface/17778 "2024-05-30T12:57:19Z")
Hi! My device is a Jetson Nano 16GB with OpenCV version 4.5.4. When running an OpenCV sample, the UI of imshow looks different from the nomal one. And in another program, it’s unable to display the video. --- ## [Error while compiling mingw msys2 c++](https://forum.opencv.org/t/error-while-compiling-mingw-msys2-c/17072)
**Author:** [@wowzie](https://forum.opencv.org/u/wowzie)\ **Replies:** 0\ **Last updated:** [March 29, 2024, 12:10am UTC](https://forum.opencv.org/t/error-while-compiling-mingw-msys2-c/17072 "2024-03-29T00:10:32Z")
so there is a problem when it compiles it tells me this error when i try running the .exe The code execution cannot proceed because Qt6Widgets. dll was not found. opencv and The code execution cannot proceed because Qt6… --- ## [Video distorted after Writing Video using Open CV with QT](https://forum.opencv.org/t/video-distorted-after-writing-video-using-open-cv-with-qt/16546)
**Author:** [@rKum](https://forum.opencv.org/u/rKum)\ **Replies:** 2\ **Last updated:** [February 22, 2024, 8:50pm UTC](https://forum.opencv.org/t/video-distorted-after-writing-video-using-open-cv-with-qt/16546 "2024-02-22T20:50:16Z")
I have a code in C++ based on QT running on windows built using visual studio 2017. In this there is a vector of pixmap images. QVector\ imageVector; The images in the vector we need to write to video f… --- ## [Undefined symbol: cv::imwrite when linking with Qt Creator](https://forum.opencv.org/t/undefined-symbol-cv-imwrite-when-linking-with-qt-creator/16332)
**Author:** [@ivelin](https://forum.opencv.org/u/ivelin)\ **Replies:** 8\ **Last updated:** [February 3, 2024, 9:17am UTC](https://forum.opencv.org/t/undefined-symbol-cv-imwrite-when-linking-with-qt-creator/16332 "2024-02-03T09:17:39Z")
Hello, I am trying to built a mobile app using CMake with Qt and OpenCV, but I get an error when running make. Those are my files CMakeLists.txt file cmake\_minimum\_required(VERSION 3.16) project(androidnotifier LANGU… --- ## [Could not load the QT platform "xcb" even though it was found](https://forum.opencv.org/t/could-not-load-the-qt-platform-xcb-even-though-it-was-found/1011)
**Author:** [@baskpann](https://forum.opencv.org/u/baskpann)\ **Replies:** 3\ **Last updated:** [December 11, 2023, 6:41am UTC](https://forum.opencv.org/t/could-not-load-the-qt-platform-xcb-even-though-it-was-found/1011 "2023-12-11T06:41:04Z")
System information (version) OpenCV =\> 4.5.1.48 Operating System / Platform =\> Ubuntu 20.10 Compiler =\> Visual Studio 2020 Detailed description I’m trying to run a face recognition algorithm in python3.8.5(in anaconda4… --- ## [Deactivate ROI dragging in imshow](https://forum.opencv.org/t/deactivate-roi-dragging-in-imshow/2251)
**Author:** [@sebko\_iic](https://forum.opencv.org/u/sebko_iic)\ **Replies:** 4\ **Last updated:** [November 30, 2023, 11:47am UTC](https://forum.opencv.org/t/deactivate-roi-dragging-in-imshow/2251 "2023-11-30T11:47:51Z")
I’m working with imshow. When you zoom into a displayed image with your mouse wheel you can use the left mouse button to drag the ROI. As I am building an application on top of imshow this is really annoying. Can you dea… --- ## [Error building Opencv4 with Qt5](https://forum.opencv.org/t/error-building-opencv4-with-qt5/15500)
**Author:** [@FellowKrieger](https://forum.opencv.org/u/FellowKrieger)\ **Replies:** 7\ **Last updated:** [November 14, 2023, 6:11pm UTC](https://forum.opencv.org/t/error-building-opencv4-with-qt5/15500 "2023-11-14T18:11:51Z")
Hello, I am encoutering an error while trying to build opencv4 with qt tools. Here are the versions used to create the build: OpenCV4.8.0 Qt5.15.2 with the tools gcc and g++ from mingw810\_32 Description of the error… --- ## [Defect in imshow() with Qt which truncates displayed XY coordinates](https://forum.opencv.org/t/defect-in-imshow-with-qt-which-truncates-displayed-xy-coordinates/14975)
**Author:** [@Brian](https://forum.opencv.org/u/Brian)\ **Replies:** 11\ **Last updated:** [October 24, 2023, 4:51pm UTC](https://forum.opencv.org/t/defect-in-imshow-with-qt-which-truncates-displayed-xy-coordinates/14975 "2023-10-24T16:51:39Z")
There is an example program to test the opencv Python install which pops up a window displaying an image and writes the mouse pointer XY coordinates to the lower left hand corner of the window. Half of the coordinates fa… --- ## [Linking opencv lib with Qt](https://forum.opencv.org/t/linking-opencv-lib-with-qt/13331)
**Author:** [@Gopal\_Sundaram](https://forum.opencv.org/u/Gopal_Sundaram)\ **Replies:** 1\ **Last updated:** [May 28, 2023, 4:52am UTC](https://forum.opencv.org/t/linking-opencv-lib-with-qt/13331 "2023-05-28T04:52:44Z")
Hello everyone. I am trying to use opencv C++ with Qt. Wondering if i need to re-compile opencv with minggw for windows 10 and link or can i link the downloaded windows version directly in .pro file. This may be an … --- ## [Exception thrown when running a sample using dnn](https://forum.opencv.org/t/exception-thrown-when-running-a-sample-using-dnn/12818)
**Author:** [@kceiw](https://forum.opencv.org/u/kceiw)\ **Replies:** 4\ **Last updated:** [April 17, 2023, 5:42am UTC](https://forum.opencv.org/t/exception-thrown-when-running-a-sample-using-dnn/12818 "2023-04-17T05:42:54Z")
Hi, I’m learning to use opencv and trying to run the sample from opencv repo but it always throws an exception. I have no idea how to debug it. What I tried is to follow this tutorial OpenCV: Load Caffe framework model… --- ## [Qt launch issue](https://forum.opencv.org/t/qt-launch-issue/1591)
**Author:** [@markworth](https://forum.opencv.org/u/markworth)\ **Replies:** 5\ **Last updated:** [April 13, 2023, 3:46pm UTC](https://forum.opencv.org/t/qt-launch-issue/1591 "2023-04-13T15:46:16Z")
I’ve been trying to build a docker image to push a simple output from opencv but keep experiencing the same error when I launch a docker image; No protocol specified qt.qpa.xcb: could not connect to display :0 qt.qpa.pl… --- ## [Imshow() not showing image for CV\_16UC3](https://forum.opencv.org/t/imshow-not-showing-image-for-cv-16uc3/12663)
**Author:** [@pralhad](https://forum.opencv.org/u/pralhad)\ **Replies:** 6\ **Last updated:** [April 12, 2023, 8:16am UTC](https://forum.opencv.org/t/imshow-not-showing-image-for-cv-16uc3/12663 "2023-04-12T08:16:15Z")
Hi, I am trying to display BGR/RGB image of 3 channels. Each channel size is 16 bits. I tried following code snippet and it shows blank image without any pixel value. But if I change “CV\_16UC3” to “CV\_8UC3”, it works. … --- ## [Opencv/pyqt python gui is crashing when i try to save an image](https://forum.opencv.org/t/opencv-pyqt-python-gui-is-crashing-when-i-try-to-save-an-image/8127)
**Author:** [@palacetrading](https://forum.opencv.org/u/palacetrading)\ **Replies:** 2\ **Last updated:** [March 27, 2022, 10:22pm UTC](https://forum.opencv.org/t/opencv-pyqt-python-gui-is-crashing-when-i-try-to-save-an-image/8127 "2022-03-27T22:22:12Z")
I have a video player GUI that is crashing when I try to save an image. I don’t get any error message in the terminal so I am not sure what is happening - this is only happening on one of the many PCs that I am running t… --- ## [Opencv with QT6](https://forum.opencv.org/t/opencv-with-qt6/2429)
**Author:** [@Yousef\_Alnaser](https://forum.opencv.org/u/Yousef_Alnaser)\ **Replies:** 3\ **Last updated:** [August 25, 2022, 8:24pm UTC](https://forum.opencv.org/t/opencv-with-qt6/2429 "2022-08-25T20:24:14Z")
I’m trying to include opencv in qt6, but in latest opencv version–\> cmakelists: it checks for qt5, and therefore, it could not detect or find my QT6. Is there any tricks or versions I should know about? I would really … --- ## [Problems with VideoCapture on Windows](https://forum.opencv.org/t/problems-with-videocapture-on-windows/9754)
**Author:** [@someoneetc](https://forum.opencv.org/u/someoneetc)\ **Replies:** 6\ **Last updated:** [August 10, 2022, 10:11pm UTC](https://forum.opencv.org/t/problems-with-videocapture-on-windows/9754 "2022-08-10T22:11:11Z")
Hello, I’m trying to port on Windows an application I wrote on Linux using Python(Qt5 and OpenCV). The problem is that, when I try to open a webcam using cv2.VideoCapture(camera) where camera is obtained as follows: s… --- ## [Read an image in Ressources QT](https://forum.opencv.org/t/read-an-image-in-ressources-qt/9710)
**Author:** [@Christophe\_Jacquelin](https://forum.opencv.org/u/Christophe_Jacquelin)\ **Replies:** 2\ **Last updated:** [August 1, 2022, 7:55am UTC](https://forum.opencv.org/t/read-an-image-in-ressources-qt/9710 "2022-08-01T07:55:38Z")
Hello, I use QT and OpenCV. How to specify an image resource file when I use imread instead of the path of the image ? Thx --- ## [Open CV Casting variables problem in QT Creator (C++)](https://forum.opencv.org/t/open-cv-casting-variables-problem-in-qt-creator-c/9688)
**Author:** [@Kamil\_Jaworski](https://forum.opencv.org/u/Kamil_Jaworski)\ **Replies:** 3\ **Last updated:** [July 30, 2022, 10:43am UTC](https://forum.opencv.org/t/open-cv-casting-variables-problem-in-qt-creator-c/9688 "2022-07-30T10:43:57Z")
Hi, I’m trying to calibrate my camera using OpenCV library in QT Creator. I’m trying to display a cv::Matx33f and cv::Vec in QT using qDebug() console or QPlainTextEdit so I could see the result in my GUI, but I have no… [Next page](https://forum.opencv.org/tag/qt/172.md?match_all_tags=true&page=1&tags%5B%5D=qt)