Hi and welcome to devnet,

Can you show the code you are using ?
What exactly do you expect ?
What exactly do you get ?

@sierdzio said in QWidget: Cannot create a QWidget without QApplication - OpenCV imshow() 2.4.13 ?:

Is Qt the only supported backend? If yes, then indeed requirements do propagate.

No, it has been added later on. It's maybe even the latest that has been implemented.

AFAIK, what the OP is hitting here, is that OpenCV doesn't have an implementation for imgshow for iOS. It would require to either use Qt to show the result of what he's doing or native stuff.

Yeah i feel like i do sudo apt-get update && upgrade at least once a day. I just checked about SIP and i compiled it from source but i cant remember if i actually used the command make and make install. Does that mean i have to reinstall pyqt5 again? I guess i just open a new thread. Thanks for all the help @SGaist

Hi,

GStreamer in OpenCV ? Shouldn't you rather post this question on either or maybe both of their forum ?

@Chris-Kawa Thank you, now it works. The solution was simple, but apparently I must understand better how the paths work. If you have any advice on where to start reading or you know any interesting online article/tutorial, please tell me :-)

Hi,

Maybe a silly question but are you sure that OpenCV is properly installed in opencvArm ?

dll paths do not influence the build so they are not included in qmake. if you use QtCreator in the right bar select project and in the build and run tab, select the run subtab and you can customise the run environment adding the paths of the dlls to the run environment PATH

otherwise you can use the INSTALLS of qmake to deploy all the binaries where you need them

Hi,

Just a quick note, taking a look at fixing this "fix", I just saw that the latest version of the contrib repository doesn't contain the offending code anymore.

@Sam_
I'm glad i could help. Please mark the Thread as "solved" if it's solved for you. :)

hello, here is a working example
https://goo.gl/2puvC1

Good !

In that case, please mark the thread as solved using the "Topic Tool" button so that other forum users may know a solution has been found :)

@SGaist
yes all opencv files is included in the path.
After some research in log file, i think I have a problème with the génération of libopencv_imgcodecs310 and libopencv_imgproc310 files.

I'll keep you posted.

@SGaist said:

Android

Hello all,

Sorry for the late reply
As SGaist said i was able to build and run qt with opencv successfully on windows desktop using mingw for desktop bundled with qt for android

Thanks
Amal

As it is not related to Qt you should ask OpenCV community.

Take a look at the answer here

ok..thanks

Use the "Topic Tool" button :)

Hi
Did you try to show vodeo capture only from the slow one? I think it might be usefull to test if the second camera slow only when image from both cameras is shown or it's always slow.

Another suggection is to try to swap devices. It may be some kind of hardware problem.

The last suggestion is to try to use QGraphicsView as soon as it might be just quicker than labels. However I don't think that the problem you described is in labels.

I downloaded and compiled opencv3 with gtk3 on, and then I installed Qt and had the same issue.

I found a work around for this is to recompile opencv with cmake and set: WITH_GTK3=OFF. And reinstall the library.

After that my Qt application work fine. Hope this helps

Hi @amahta ,

I was browsing the applications you have written, and they look really good.
Would you be interested in having them presented in the Qt Showroom? http://showroom.qt.io

They would be a good fit there, as they show off using Qt together with OpenCV in a practical way.
Ping me on chat if you are interested.

Tero // Online Community Manager

Thanks @tekojo and of course Qt.
Image Transformer is now being displayed in Qt Showroom:
https://showroom.qt.io/image-transformer/

@David_Dev said:

. Is it easy to convert a OpenCV TIFF image into a Qt TIFF image ?

OpenCV use cv::Mat to store Image data , but Qt use QImage / QPixmap. You need to make a conversion function.

Just Google it and you will find example code:

Qt and openCV: Convert between cv::mat and Qimage correctly

Hi and welcome to devnet,

The first thing to do is verify that the compiler used to build OpenCV matches the one used for Qt.

As for using OpenCV and Qt together, please search this forum, it's a question that has been asked and answered many times already.

Can you share your pro file ?

That's a bit of a strange question, you want GUI within a console application ?

I think, that it is hardly related to the OpenCV lib, as this problem does not occur when using this library in Microsoft Visual C++ Express 2010. The main reason I do not use MinGW - as OpenCV library contain files for VS2010 (the version of the library I use - is 2.4.9 - with the support of VS2010).

The version of Qt - 5.4.2/5.5.0 that support MSVC 2010.

@Chris-Kawa thank you for your response! I know that there is no 64bit VS, and you are right about the 64 bit builds, I just don't know how to do it :) I managed to get rid of the problem written above by removing qtmain.lib from the lib listing, and VS builds the app succesfully. I just downloaded the 64 bit Qt version and will try it, hope it will be fine with MD and MDd settings.

Sandy,
Thank you VERY MUCH! Your directions seemed to work. I did have to make a bunch of changes, but finally figured it out. The changes were in the PATHs. Now I need to go through the resulting compiler code and see if it all got loaded and is going to work properly.
Again, THANKS!
Bob

Problem is solved thanks to user berak at OpenCV forum.

For other users who can have this problem solution is as follows:

some modules have changed in 3.0. to use imread()/imwrite, add:
LIBS += "E:\OpenCV\release\lib\libopencv_imgcodecs300.dll.a"

Regards

@Duino said:

I just meet a bug ghost in my code.That means if I try to find what happen inside,the code runs well.But if I don't, bugs happen.

It's not a ghost. It's a Heisenbug :)

How should I catch this bug ghost???

Simplify your program, do unit testing. and use a tool like Valgrind.

I still come out to the same error.

Hi and welcome to devnet,

To add to @koahnig , your application is probably not finding the OpenCV dlls. You would need to update the PATH variable in the Run part of the Project panel.

Hi,

If my cv::Mat variable is a 2 dimension matrix of a small size (<10*10）, is it possible to show its elements in "locals and expressions" window? Is it easy or lots of work needed? Or there has already been some tools?

Thanks a lot.
Yanming