libopencv-2.3.1

In ROS(Electric) the package opencv2 is deprecated. Instead, libopencv-dev 2.3.1 is used as the source of OpenCV. However it comes with some troubles in linking the library as the PKG_CONFIG_PATH will automatically add -I to the libraries(2.3.1), there would be error when linking. Meanwhile the libopencv-dev 2.3.1 uses opencv-2.3.1.pc instead of opencv.pc in usr/lib/pkgconfig/, which will cause the following error when compiling out of ROS for the regular c/cpp source file although the pkg-config is set to the opencv-2.3.1.pc.


/usr/bin/ld: cannot find -l/usr/lib/libopencv_contrib.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_legacy.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_objdetect.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_calib3d.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_features2d.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_video.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_highgui.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_ml.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_imgproc.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_flann.so.2.3.1
/usr/bin/ld: cannot find -l/usr/lib/libopencv_core.so.2.3.1
collect2: ld returned 1 exit status
make: * [DisplayImage] Error 1


To solve the problem, the method that works on my computer is to create an additional .pc file at /usr/lib/pkgconfig/opencv.pc with the following contents.[1]

1:  # Package Information for pkg-config  
2:  prefix=/usr  
3:  exec_prefix=${prefix}  
4:  libdir=${exec_prefix}/lib  
5:  includedir_old=${prefix}/include/opencv-2.3.1/opencv  
6:  includedir_new=${prefix}/include/opencv-2.3.1  
7:  Name: OpenCV  
8:  Description: Open Source Computer Vision Library  
9:  Version: 2.3.1  
10:  Libs: -L${libdir} -lopencv_contrib -lopencv_legacy -lopencv_objdetect -lopencv_calib3d -lopencv_features2d -lopencv_video -lopencv_highgui -lopencv_ml -lopencv_imgproc -lopencv_flann -lopencv_core  
11:  Cflags: -I${includedir_old} -I${includedir_new}  

Reference
[1]about compiling opencv programs outside ROS, http://answers.ros.org/question/11916/about-compiling-opencv-programs-outside-ros
[2]Ticket #1475, https://code.ros.org/trac/opencv/ticket/1475