I'm currently struggling to build OpenCV for the UWP.
I already googled quite a lot and found Microsoft's OpenCV Github Repo which tecnically should do the magic. However, this repo and pretty much everything else I found in this regard are outdated (Visual Studio 2015, old OpenCV versions etc.). I need to use OpenCV 3.3 because it's a cross platform project and I don't want to recompile everything else solely because of an outdated git repo.
Can anyone explain the process of building OpenCV using CMake from the official repo for the UWP?
My first attempt was to simply use the Windows Dlls, however my application than shouts "Failed to load module" at me. Then, I tried to build OpenCV the Visual Studio Project files as stated here and here. However, this doesn't do it for me as it throws the following error:
CMake Error at cmake/OpenCVUtils.cmake:440 (if):
if given arguments:
"(" "OR" "OFF" ")"
Unknown arguments specified
Call Stack (most recent call first):
CMakeLists.txt:317 (OCV_OPTION)
It also tells me to check the CMakeOutput.log but there it's 0 errors everywhere.
If someone could tell me either how to get rid of this error or what to change in the CMake GUI to build OpenCV for UWP, that'd be great!
Edit:
I also tried to compile OpenCV with a platform specific toolchain for WinRT as found in platforms/winrt. It doesn't really change anything though (I'm not even sure if it should), I still get "Unable to load Dll: The specified module could not be found". Maybe GPPK is right in his assumption that it's more an UWP problem than an OpenCV one. Anyways, if anyone knows anything about this, I'd really love to get some help!
Ok, I didn't get an answer yet, so I managed to do it myself (more or less).
Here's how I did it:
Prerequisites
Visual Studio (2017)
UWP SDK
CMake
OpenCV from official repo
Steps
Create a build folder which you want the UWP libraries to built in.
Start PowerShell in this folder and execute the following command (exchange C:\OpenCV with your local OpenCV path): cmake -G "Visual Studio 15 2017" -DCMAKE_SYSTEM_NAME=WindowsStore -DCMAKE_SYSTEM_VERS
ION="10.0" -DCMAKE_VS_EFFECTIVE_PLATFORMS=x86 -DBUILD_TESTS=OFF -DBUILD_PERF_TESTS=OFF C:\OpenCV
If you get the same error message as I did (see question for more details), go to the root CMakeLists.txt in the OpenCV folder and add a # in front of line 317 (OCV_OPTION(ENABLE_PYLINT)). This should fix it, to check, execute the command from above once more.
Ensure that the output claims "Windows RT support YES" and "Building for Microsoft platform: Windows".
Open OpenCV.sln in the build folder. Ensure that all projects are either of type "Windows Store" or "Universal Windows" and build the ALL_BUILD Project twice: Once in Release configuration, and once in Debug. Then build the INSTALL Project.
That's it, you should find the built Dlls in the install folder. Step 3 is probably a bug in OpenCV and will hopefully be fixed in upcoming versions.
I installed OpenCV 2.4.13 after installing the required dependencies and I'm running it with Qt Creator 5.7 for programming in C++. Following some tutorials I managed to load still images, process them and so on. But when I try to use the cv::VideoCapture, for example:
cv::VideoCapture cap;
cap.open("<File location/file name>");
or:
cv::VideoCapture("<File location/file name");
cap.isOpened() always return false. Even if I try to ignore this and go further with Mat, read, imshow and so on, the program crashes. I've already tried everything about loading the file: giving a std::string as argument, giving a *char, putting the video file on easier locations, in the project directory and nothing works. I tried with two different .mp4, with a .mov and with the cube4.avi file given in the "samples" folder (from openCV examples). All these files are perfectly played by my VLC. I've already tried in Qt with a QtWidgets project and with a plainCpp project. It never works. After searching about it, I've seen that this bug is very recurrent, but I've just found solutions for Windows, regarding on adding a .dll file to the project. But what should I do on Ubuntu, since Linux uses no dlls?
I figured out how to solve this and I'm here to share with everyone who encounter similar problems. First of all, my FFmpeg installation was for any unknown reason ignored on the OpenCV compilation. Since FFmpeg is needed to read and write videos, OpenCV wasn't able to do these jobs and displayed no error or warning messages about that. Anyway I decided to try everything again from the beginning. Keep in mind: if you just reinstall FFmpeg, it's not going to solve your problems; after that you have to do cmake, compile and install OpenCV again. I downloaded the most recent version of FFmpeg from the repository, compiled and installed it again. I tried to compile OpenCV again, but it was always stuck at about 15% when processing a FFmpeg (Libav) .h file with the message:
<file_name.h> can not be used when making a shared object; recompile with -fPIC
So I searched for it and with some effort I found out that it was necessary to compile the FFmpeg with the following configure line before doing the make:
.\configure --enable-pic --enable-shared
Some ffmpeg installation tutorials include even more commands after "configure". Then I compiled and reinstalled FFmpeg and compiled and reinstalled OpenCV. After that, I was able to load videos (the cap.isOpened() was no longer false), but nonetheless I was getting the following error for any video and they weren't being read:
Assertion desc failed at libswscale/swscale_internal.h:674
The way I found to solve this was downloading the newest stable FFmpeg version instead of the newest on, compiling it again, compiling OpenCV again and then it was successful! Now I can both load and write video files (I haven't tested it with multiple codecs yet). I wonder why they don't launch pre-compiled versions of OpenCV with everything so that we don't need to deal with all these stuffs...
Summarizing everything:
Download the last stable release of FFmpeg. If it doesn't work, try an older one. (I'm using the 2.8.6, the last stable right now).
Unpack it, open the terminal from the ffmpeg folder, compile and install it typing:
.\configure --enable-pic --enable-shared
make
sudo make install
Download OpenCV (if you haven't done it yet), unpack and install it following the official linux installation tutorial:
http://docs.opencv.org/2.4/doc/tutorials/introduction/linux_install/linux_install.html#linux-installation
I solve the problem by install "opencv3.2.0-dev" instead "opencv3.2.0";
pip install opencv-python is not enough to install OPENCV.
I am trying to build and use a piece of C++ code that uses OpenCV. I am working on Linux, working in Code::Blocks (and the code was originally also developed on a Linux platform using C::B).
I followed this to install OpenCV (Ubuntu 12.04 & OpenCV 2.4.3). The project compiles fine, but when I try to execute it, it crashes on launch, with the following message about how it can not find the library:
(file_address): error while loading shared libraries: libopencv_core.so.2.3:
cannot open shared object file: No such file or directory
Process returned 127 (0x7F) execution time : 0.017 s Press ENTER to continue.
I set all the parameters for the linker according to several Code::Blocks install tutorials.
I also checked in /usr/local/lib/ for my libraries (it is the folder I gave to Code::Blocks' compiler); and while I do have a libopencv_core.so, a libopencv_core.so.2.4 and a libopencv_core.2.4.3, I do not have a libopencv_core.so.2.3.
So I'm wondering what the issue is. Is it about backwards compatibility, i.e. do I have to install the exact same version of OpenCV used to develop the original code? (This would be a bit concerning, since I am trying to make a widely-usable library).
Could I force it to use libopencv_core.so.2.4 instead?
EDIT: I managed to make it work by removing everything and reinstalling with a simple apt-get. Sometimes it's the simplest method that works the best! From now on I'll try to apt-get before following installation tutorials. ;)
Have a nice day!
I downloaded the offline Qt 5.1.1 (32-bit) package from the website. Just installed it on my Ubuntu 12.04 machine. I had installed build-essentials prior to the Qt install.
I opened a new Application/GUI project in Qt Creator to play around with. Haven't added anything to it yet so it just has its default files. I tried to build it using the Creator Build button and it throws errors:
:-1: error: skipping incompatible /home/Me/Qt5.1.1/5.1.1/gcc/lib/libQt5Widgets.so when searching for -lQt5Widgets
:-1: error: cannot find -lQt5Widgets <
Does same thing for the QtCore/Gui files.
Decided to open one of the examples that was included with Qt. Then built it. It also threw the same errors.
What's wrong? My extra reading said something about adding a QT += widgets line in the .pos file but that seems to be there, automatically, inside a version checker.
I thought this was going to be working out of the box? What have I missed?
Turns out Frank was right. While I was correct that I downloaded the 32-bit version of QT I was incorrect about what I was running on the Lenovo for an OS. I'm actually running the 64-bit Linux. Didn't think this old thing had the 64-bit loaded on it. Doh!
Downloaded the 64-bit QT and problem solved.
Thanks Frank for the heads up.
I would like to create a gui application with Qt, using opencv on Windows XP. I used both Qt and opencv before, but never together. Long story short, I'm unable to get opencv work with Qt.
As on all the forums I searched there are just little pieces of information scattered around, usually with no answer, I summarize here all the steps I've taken.
Downloaded the Qt SDK (4.6.3) for Windows, and used it for some time, successfully.
Downloaded the opencv 2.3.1 megapack for Windows, complete with binaries. I managed to compile my Qt project including opencv successfully, but any opencv function call resulted in a crash. I read on some forums that the binaries in the Windows megapack don't support Qt, and I have to build opencv myself
I downloaded the latest version of CMake (2.8).
I downloaded the source of opencv from here: http://code.opencv.org/svn/opencv/branches/2.3/
I downloaded the source for the version of Qt I had (4.6.3)
I found my old version of visual Studio 2005
I created a VS2005 project with CMake, checking the support for Qt. (WITH_QT checked)
I built opencv in VS2005. It created most of the libraries, but not all. Highgui was among the failed ones. The problem: Qt\4.6.3\src\corelib\global\qconfig.h was not found. There was no qconfig.h at all in the source I downloaded! I found some templates qconfig-large.h, qconfig-small.h etc., so I renamed one of them to qconfig.h. Now I got a screen full of linker errors.
I downloaded the latest Qt source instead (4.8.1). Now there is a source file qbenchmark.h that includes QtTest/qbenchmarkmetric.h which cannot be found.
I gave up, and tried MinGW.
I downloaded the latest MinGW (2011.11.18)
I set CMake to generate a MinGW makefile, but I got the following error:
.
CMake Error at C:/Program Files/CMake 2.8/share/cmake-2.8/Modules/Platform/Windows-g++.cmake:1 (INCLUDE):
include could not find load file:
C:/Program Files/CMake 2.8/share/cmake-2.8/Modules/Platform/Windows-gcc.cmake
Call Stack (most recent call first):
C:/Program Files/CMake 2.8/share/cmake-2.8/Modules/CMakeCXXInformation.cmake:59 (INCLUDE)
True, there is a Windows-g++.cmake file in the Modules/Platform directory, but it references Windows-gcc.cmake which does not exist!
Is there anyone who managed to build opencv with Qt support on Windows, and if yes, how?
Edit:
The problem is definitely with the Qt source. I managed to generate a MinGW makefile, and the build went all OK until it stopped in src/testlib/qtestsystem.h because there was an include for QtCore/qelapsedtimer.h which file is in a completely different directory! Does Qt release incomplete sources, or did I do something wrong?
Edit2
My torment continues. I cleaned everything and started anew. This time without even trying Visual Studio.
I downloaded the latest Qt libs with source (4.8.1)
I downloaded the latest MinGW (2011.11.18)
With CMake I successfully created a Makefile, and built it with MinGW. I got some shiny new libs (libopencv_core231, etv.). I was very happy, but how wrong I was to celebrate that soon!!
I downloaded the latest Qt SDK (strangely, it was 4.8.0, so I set Qt Creator to use the 4.8.1) and created a test program without opencv to see if it works. It worked!
I tried using opencv, just reading and displaying an image. It didn't work. exited with code -1073741511
I tried running the .exe directly, outside of Qt Creator. It complained of a missing libstdc++-6.dll
I did a search for it, and found on in my MinGW install (c:\mingw\bin, 958 KB), and one in my Qt install (c:\qt\mingw\bin, 793 KB) - this mingw came bundled with Qt.
I tried both, by copying them in the same folder where my .exe is, but neither worked. I got "The procedure entry point _ZNSt9exceptionD2Ev could not be located in the dynamic link library libstdc++-6.dll." with both. This was in debug, so I tried release, and I got a similar error, with some other entry point not found.
I searched the forums, and I found suggestions that I should link libstdc++ statically. I inserted -static-libgcc -static-libstdc++ at the lines QMAKE_LFLAGS = and QMAKE_LFLAGS_DEBUG = in the file c:\Qt\mkspecs\win32-g++\qmake.conf. This had no effect at all, even after restarting Qt Creator and rebuilding. If I don't copy the libstdc++-6.dll, it still requires it.
Of course, my simple test program without opencv runs from the exe without needing any libstdc++-6.dll, so that means my opencv build is responsible? I wanted to build opencv anew, but I cannot find any CMake settings referring to libstdc++ !
It might be a clue:
When using one of the libstdc++-6.dll files, the error about a missing entrypoint mentions QtGui4.dll. I have a debug build, so it should be QtGui*d*4.dll, shouldn't it? Are there different libstdc++s for debug and release? Either way, I tried to build release, but it didn't work either, same error
Is there no single person on this planet who tried using Qt with QtCreator and opencv 2.3 together on Windows xp, and succeeded? From searching all the forums and Qt archives, I could not find anyone. I'm ready to do the development in Linux, but I'll need a Windows release sooner or later anyway.
I'm trying to resist the temptation of the dark side, which whispers into my ears to forget Qt, MinGW, g++, opencv and try to hack together something in Visual Basic. Oh, the horrors!
Just FYI, I went basically through the same nightmare of combining Qt and OpenCV. This was my experience:
I downloaded the Qt SDK 4.7.4 with Qt Creator 2.4.1 and installed it, no problem.
I downloaded and installed OpenCV 2.4.2 and not knowing that it already came with MinGW...
I downloaded the MinGW compiler which of course had a different version than the one which came already with Qt
This completely messed up my CMake, even when I explicitly told CMake to use the Qt gcc.exe and g++.exe it also used some stuff from my freshly installed MinGW. Probably because I eagerly added every directory to my PATH variable. What a fool I was!
CMake was not able to generate any useful files, so I gave up and installed the OpenCV superpack, hoping this would make things easier.
6.I spent hours wondering, why Qt and OpenCV from the superpack didnt work properly together. I never quite understood. I had the same errors that other users describe here, like console programs crashing as soon as some OpenCV was included. The strange thing is, that I could start the executable manually from FileExplorer (I added all .dlls you could think of to the project folder: opencv_core242.dll, opencv_highgui242.dll, QtCore4.dll, QtGui4.dll and so on...) BUT I could not launch my little test program from within the Qt Creator environment.
I analysed if there was a problem with my DLLs using depends.exe and found out that even though I configured everything to be in DEBUG using the MinGW compiler, my program still tried to use QtCore4.dll and not QtCore4d.dll... So my best guess was, that it was mixing debug and release version.
I gave up using the superpack and again tried to use CMAKE first and then build OpenCV using the Qt MinGW version AND making sure to setup everything for Debug mode and enable the QT option. But no luck with that so far
I stopped using MinGW and switched over to MSVC2010, which works better. However I am still not able to debug the program since the MSVC2010 debugger engine seems to be missing. I dont really know how to manually add this but I am still working on it
So what I can definitely tell is that using Qt and OpenCV for somebody who has little experience is far from trivial!
You should build OpenCV from source, as you already did, it is no hassle. Note that recent versions of OpenCV can be built with and w/o Qt. Highgui optionally uses Qt! It is your choice if you build with or without Qt.
I used Qt libraries together with OpenCV for long time now. I never went for the SDK, instead I used the libs which are built for corresponding VS version. See here: http://qt.nokia.com/downloads/downloads#qt-lib
You can have it for VS2008 and VS2010, but earlier versions are also available built for VS2005. Old versions of Visual Studio suck so hard, why use them anyway.
Then I never had problems pulling it together in a CMake project. It goes along the lines of:
find_package(OpenCV)
find_package(Qt4 ${VOLE_MINIMUM_QT_VERSION} COMPONENTS QtCore QtGui)
find_package(Qt4 ${VOLE_MINIMUM_QT_VERSION} COMPONENTS QtOpenGL)
...
qt4_wrap_cpp(moc_sources ${vole_module_moc_sources})
qt4_wrap_ui(uic_sources ${vole_module_ui_sources})
qt4_add_resources(rcc_sources ${vole_module_rcc_sources})
You know, the usual stuff.
Five man weeks later you may probably get it run under Windows, while under GNU/Linux it is three commands in the shell.
You might have an easier time configuring Qt Creator with OpenCV. This post shows how to achieve that, step-by-step! It displays several screenshots to aid in the process too.