Use OpenCV in mex function : error after compilation - c++

Question

I am working on a project developed under matlab, but I had to use C ++ and OpenCV.
In order to integrate my work with the project, I need to use mex-files. So I installed Matlab 2013 on my computer and gcc 4.4.
I modified the file ~/.matlab/R2013a/mexopts.sh in order to set the right compiler and options for opencv.
This is the output of the compilation in matlab with mex -v
**************************************************************************
Warning: Neither -compatibleArrayDims nor -largeArrayDims is selected.
Using -compatibleArrayDims. In the future, MATLAB will require
the use of -largeArrayDims and remove the -compatibleArrayDims
option. For more information, see:
http://www.mathworks.com/help/matlab/matlab_external/upgrading-mex-files-to-use-64-bit-api.html
**************************************************************************
-> mexopts.sh sourced from directory (DIR = $PREF_DIR)
FILE = /home/amine/.matlab/R2013a/mexopts.sh
----------------------------------------------------------------
-> MATLAB = /usr/local/MATLAB/R2013a
-> CC = gcc-4.4
-> CC flags:
CFLAGS = -std=c99 -D_GNU_SOURCE `pkg-config --cflags opencv` -fexceptions -fPIC -fno-omit-frame-pointer -pthread
CDEBUGFLAGS = -g
COPTIMFLAGS = -O -DNDEBUG
CLIBS = -Wl,-rpath-link,/usr/local/MATLAB/R2013a/bin/glnxa64 -L/usr/local/MATLAB/R2013a/bin/glnxa64 -lmx -lmex -lmat -lm -lstdc++
arguments = -DMX_COMPAT_32
-> CXX = g++-4.4
-> CXX flags:
CXXFLAGS = -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread
CXXDEBUGFLAGS = -g
CXXOPTIMFLAGS = -O -DNDEBUG
CXXLIBS = -Wl,-rpath-link,/usr/local/MATLAB/R2013a/bin/glnxa64 -L/usr/local/MATLAB/R2013a/bin/glnxa64 -lmx -lmex -lmat -lm
arguments = -DMX_COMPAT_32
-> FC = gfortran
-> FC flags:
FFLAGS = -fexceptions -fbackslash -fPIC -fno-omit-frame-pointer
FDEBUGFLAGS = -g
FOPTIMFLAGS = -O
FLIBS = -Wl,-rpath-link,/usr/local/MATLAB/R2013a/bin/glnxa64 -L/usr/local/MATLAB/R2013a/bin/glnxa64 -lmx -lmex -lmat -lm
arguments = -DMX_COMPAT_32
-> LD = g++-4.4
-> Link flags:
LDFLAGS = -pthread -shared -Wl,--version-script,/usr/local/MATLAB/R2013a/extern/lib/glnxa64/mexFunction.map -Wl,--no-undefined /usr/local/lib/libopencv_calib3d.so /usr/local/lib/libopencv_contrib.so /usr/local/lib/libopencv_core.so /usr/local/lib/libopencv_features2d.so /usr/local/lib/libopencv_flann.so /usr/local/lib/libopencv_gpu.so /usr/local/lib/libopencv_highgui.so /usr/local/lib/libopencv_imgproc.so /usr/local/lib/libopencv_legacy.so /usr/local/lib/libopencv_ml.so /usr/local/lib/libopencv_nonfree.so /usr/local/lib/libopencv_objdetect.so /usr/local/lib/libopencv_ocl.so /usr/local/lib/libopencv_photo.so /usr/local/lib/libopencv_stitching.so /usr/local/lib/libopencv_superres.so /usr/local/lib/libopencv_ts.a /usr/local/lib/libopencv_video.so /usr/local/lib/libopencv_videostab.so /usr/lib/x86_64-linux-gnu/libXext.so /usr/lib/x86_64-linux-gnu/libX11.so /usr/lib/x86_64-linux-gnu/libICE.so /usr/lib/x86_64-linux-gnu/libSM.so /usr/lib/x86_64-linux-gnu/libGL.so /usr/lib/x86_64-linux-gnu/libGLU.so -ltbb -lrt -lpthread -lm -ldl
LDDEBUGFLAGS = -g
LDOPTIMFLAGS = -O
LDEXTENSION = .mexa64
arguments =
-> LDCXX =
-> Link flags:
LDCXXFLAGS =
LDCXXDEBUGFLAGS =
LDCXXOPTIMFLAGS =
LDCXXEXTENSION =
arguments =
----------------------------------------------------------------
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "mxFunction.cpp"
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "verifAndHyp.cpp"
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "../Description/Statistic/statistic.cpp"
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "../Description/Statistic/classes.cpp"
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "../Verification/contradiction.cpp"
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "../HypothesisGeneration/hypothesis.cpp"
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "../Description/HoughTransform/hough.cpp"
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "../Description/HoughTransform/utils.cpp"
-> g++-4.4 -c -I/usr/local/MATLAB/R2013a/extern/include -I/usr/local/MATLAB/R2013a/simulink/include -DMATLAB_MEX_FILE -D_GNU_SOURCE `pkg-config --cflags opencv` -fPIC -fno-omit-frame-pointer -pthread -DMX_COMPAT_32 -O -DNDEBUG "../Verification/distance.cpp"
-> g++-4.4 -O -pthread -shared -Wl,--version-script,/usr/local/MATLAB/R2013a/extern/lib/glnxa64/mexFunction.map -Wl,--no-undefined /usr/local/lib/libopencv_calib3d.so /usr/local/lib/libopencv_contrib.so /usr/local/lib/libopencv_core.so /usr/local/lib/libopencv_features2d.so /usr/local/lib/libopencv_flann.so /usr/local/lib/libopencv_gpu.so /usr/local/lib/libopencv_highgui.so /usr/local/lib/libopencv_imgproc.so /usr/local/lib/libopencv_legacy.so /usr/local/lib/libopencv_ml.so /usr/local/lib/libopencv_nonfree.so /usr/local/lib/libopencv_objdetect.so /usr/local/lib/libopencv_ocl.so /usr/local/lib/libopencv_photo.so /usr/local/lib/libopencv_stitching.so /usr/local/lib/libopencv_superres.so /usr/local/lib/libopencv_ts.a /usr/local/lib/libopencv_video.so /usr/local/lib/libopencv_videostab.so /usr/lib/x86_64-linux-gnu/libXext.so /usr/lib/x86_64-linux-gnu/libX11.so /usr/lib/x86_64-linux-gnu/libICE.so /usr/lib/x86_64-linux-gnu/libSM.so /usr/lib/x86_64-linux-gnu/libGL.so /usr/lib/x86_64-linux-gnu/libGLU.so -ltbb -lrt -lpthread -lm -ldl -o "mxFunction.mexa64" mxFunction.o verifAndHyp.o statistic.o classes.o contradiction.o hypothesis.o hough.o utils.o distance.o -Wl,-rpath-link,/usr/local/MATLAB/R2013a/bin/glnxa64 -L/usr/local/MATLAB/R2013a/bin/glnxa64 -lmx -lmex -lmat -lm
But when I try to use the mxFunction like this mxFunction('path_to_my_file'), the result is :
Invalid MEX-file '/home/amine/Stage2A/stage2a/src/HypothesisGeneration/mxFunction.mexa64': /usr/local/lib/libopencv_ocl.so.2.4: undefined symbol:
_ZTIN2cv16ParallelLoopBodyE
Could you help to resolv this problem ?
PS : I'm using ubuntu 14.04 and Opencv 2.4.8

Answer 1

If you would like to compile a C/C++ file containing OpenCV code into a MEX-file I strongly recommend that you use mexOpenCV instead of mex.
Have a look at this site to set it up properly:
http://de.mathworks.com/help/vision/ug/opencv-interface.html?refresh=true
It tells you how to install the visionSupportPackages which are mandatory to compile OpenCV code into a mex file.