pkg-config --cflags opencv: No such file or directory

Question

I'm writing a basic example of opencv, but make command give me message

g++-4.7.real: error: pkg-config --cflags opencv: No such file or directory

g++-4.7.real: error: pkg-config --libs opencv: No such file or directory

issue command pkg-config --cflag opencv give me result as:

-I/usr/local/include/opencv -I/usr/local/include

and pkg-config --libs opencv give me:

-I/usr/local/include/opencv -I/usr/local/include
vudao@vudaopc:~/work/nmath/ntrainer$ pkg-config --libs opencv /usr/local/lib/libopencv_contrib.a /usr/local/lib/libopencv_stitching.a /usr/local/lib/libopencv_nonfree.a /usr/local/lib/libopencv_superres.a /usr/local/lib/libopencv_ocl.a /usr/local/lib/libopencv_ts.a /usr/local/lib/libopencv_videostab.a /usr/local/lib/libopencv_gpu.a /usr/local/lib/libopencv_photo.a /usr/local/lib/libopencv_objdetect.a /usr/local/lib/libopencv_legacy.a /usr/local/lib/libopencv_video.a /usr/local/lib/libopencv_ml.a /usr/local/lib/libopencv_calib3d.a /usr/local/lib/libopencv_features2d.a /usr/local/lib/libopencv_highgui.a /usr/local/share/OpenCV/3rdparty/lib/libIlmImf.a /usr/local/share/OpenCV/3rdparty/lib/liblibjasper.a /usr/local/share/OpenCV/3rdparty/lib/liblibtiff.a /usr/local/lib/libopencv_imgproc.a /usr/local/lib/libopencv_flann.a /usr/local/lib/libopencv_core.a /usr/lib/i386-linux-gnu/libbz2.so /usr/lib/i386-linux-gnu/libpng.so /usr/lib/i386-linux-gnu/libjpeg.so /usr/lib/i386-linux-gnu/libz.so -lswscale -lavformat -lavutil -lz -lSDL -lasound -lavcodec -lgthread-2.0 -lglib-2.0 -lgobject-2.0 -lfontconfig -lfreetype -lpango-1.0 -lcairo -lgdk_pixbuf-2.0 -lpangocairo-1.0 -lpangoft2-1.0 -lgio-2.0 -latk-1.0 -lgdk-x11-2.0 -lgtk-x11-2.0 -lrt -lpthread -lm -ldl -lstdc++

Below is my Makefile:

CC=g++
CFLAGS=-O2 -g 'pkg-config --cflags opencv'
LDFLAGS='pkg-config --libs opencv'

BIN=ntrainer

ntrainer : ntrainer.cpp
    $(CC) $(CFLAGS) $(LDFLAGS) -o $(BIN) ntrainer.cpp

My system is Ubuntu 12.10. I have installed opencv-2.4.7 successfully (I think) following instructions here http://www.samontab.com/web/2011/06/installing-opencv-2-2-in-ubuntu-11-04/

I also have configured and exported PKG_CONFIG_PATH into /etc/bash.bashrc, I'v also ran ldconfig

Please someone tell me what I'm missing? And how to correct it. Thanks too much.

Answer 1

You used incorrect quotes. You should use ` instead of ':

CC=g++
CFLAGS=-O2 -g `pkg-config --cflags opencv`
LDFLAGS=`pkg-config --libs opencv`

Answer 2

For me, the file was there but the path was wrong:

I had to look for the opencv.pc file, make sure it is in the path for the pkgconfig program to find (i.e. in one of the pkgconfig folders) and then make sure the prefix path in there is right.

In my case it was wrong because it was not installed via make install but i made a make package package because it was cross-compiled, and the path I had installed it at didn't match the CMAKE path.

running

pkg-config --cflags opencv

or

pkg-config --libs opencv

tells you where it is looking for the files, so you can make sure they match.