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I am building a project using Opencv 3.1 and wxwidgets 3.1. The code I use: [wxOpenCv Demo1]

I try to add a write frame object, using the function cv::imwrite(). (I changed the c calls to c++ eg: cvQueryFrame( m_pCapture ) to m_pCapture >> m_CurFrame;)

I get this error:

Undefined symbols for architecture x86_64:

"cv::imwrite(cv::String const&, cv::_InputArray const&, std::vector > const&)", referenced from:

CCamera::SaveFrame() in camera.o

ld: symbol(s) not found for architecture x86_64

clang: error: linker command failed with exit code 1 (use -v to see invocation)

Without wxwidgets the opencv functions work fine. So its seems that it has to do with the combination of wxwidgets and opencv.

This works fine with wxwidgets and Opencv:

cv::imshow("tmp",m_CurFrame);
cv::waitKey(4);
//      cv::imwrite(Tmp , m_CurFrame);

If I uncomment the last line, I get the error.

OS X: 10 Yosemite and I use the default compiler (Apple LLVM 7.0)

I have no idea what to do about this!

Don Quichot
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  • @DanQuichot, What is you OS/compiler? – Igor May 16 '16 at 14:00
  • OS X 10 Yosemite and I use the default compiler (Apple LLVM 7.0) – Don Quichot May 17 '16 at 06:41
  • can you show what types you are passing to imwrite? – Igor May 17 '16 at 13:25
  • cv::Mat m_CurFrame; m_pCapture >> m_CurFrame; // get a new frame from camera std::string Tmp = "Test.jpg"; cv::imwrite(Tmp , m_CurFrame); – Don Quichot May 17 '16 at 15:30
  • according to http://docs.opencv.org/3.1.0/d4/da8/group__imgcodecs.html#gabbc7ef1aa2edfaa87772f1202d67e0ce cv::imwrite() takes 3 parameters. You pass only 2. – Igor May 17 '16 at 15:47
  • The last parameter is optional. The code works fine if I do not use wxwidgets. (See e.g.http://docs.opencv.org/2.4/doc/tutorials/introduction/load_save_image/load_save_image.html). The error is a linker error. – Don Quichot May 17 '16 at 21:57
  • sorry, I'm out of ideas. Try to ask on the forums.wxwidgets.org or post to wx-users ML. You can also try asking on wxwidgets IRC channel. – Igor May 17 '16 at 23:06
  • I cannot help you but I would be happy to know if you can compile this code with XCode (wxwidgets opencv plplot and openscenegraph) https://github.com/LaurentBerger/wxOpenCV – LBerger Jun 05 '16 at 20:34

1 Answers1

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solved the problem (and more) by recompiling wxwidgets 3.1.0 and Opencv 3.1. I used these links to get it going.

Small guide to compiling wxWidgets, Opencv against C++ 11:

Compile wxwidgets 3.1.0: I followed the install.txt for OSX. And tweaked the ../configure call with help from this

I added: --enable-debug and changed the macosx version

../configure --disable-shared --enable-debug --enable-unicode --with-cocoa --with-macosx-version-min=10.7 --with-macosx-sdk=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk CXXFLAGS="-std=c++0x -stdlib=libc++" CPPFLAGS="-stdlib=libc++" LIBS=-lc++

Then with the help of this page I build a xcode project. Tweaking a few things: (wxcocoa.xcodeproj and minimal.xcodeproj, and a all new projects)

  • Add to the Header Search Path: $(WXROOT)/build/osx (to find wx.xcconfig)
  • base SDK: latest OS X (10.11)
  • C language dialect: GNU 11(not sure if this is right)
  • C++ language dialect: GNU++11 [-std=gnu++11]
  • C++ Standard Library: libc++ (LLVM C++ standard library with C++ 11 support)
  • placed the WXROOT under “preference->locations->Source Trees. Not important, but seems to be a better location (restart xcode)
  • in wxcocoa.xcconfig I changed: MACOSX_DEPLOYMENT_TARGET = 10.10
  • Somehow I have to change the name of the created library from libwx_osx_cocoa_static.a to: lwx_osx_cocoa_static.a (why, I do not know)

I use GNU++ 11 and thus libc++ to be able to use new functionality like “future" I then added OpenCV to my newly created wxXcode project:

  • Compile OpenCV following this: (search the web for: howto-install-build-and-use-opencv-macosx-10-10)
  • Make sure that the SDK is the right version (here was my biggest problem), matching the build of wxWidgets

  • The compiler settings same as for wxWidgets (see above) (added:) To do this I added some lines to the CMakeLists.txt in the (Opencv-master folder). Below the line: # OpenCV compiler and linker options (I found this trick here: search the web for: OpenCV with C++11 on OS X 10.8

    message("Setting up Xcode for C++11 with libc++.") set(CMAKE_XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++0x") set(CMAKE_XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++")

  • Then follow this page to update the newly created wxWidgets xcode project (search the web for: howto-setup-xcode-6-1-to-work-with-opencv-libraries)

This should do the trick! I can now combine wxWidgets, OpenCV and the libc++ (multithreading, “future")

I hope this helps. Please let me know if you found out more!

Don Quichot
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