Compiling opencv samples: unknown cmake command ocv_check_dependencies - opencv

Question

I am trying to build the OpenCV samples which come with the source package and I get the following:
CMake Error at CMakeLists.txt:10 (ocv_check_dependencies):
Unknown CMake command "ocv_check_dependencies".
I did install OpenCV using
cmake .
make
sudo make install
and I got a tutorial snippet working (thus I suppose it is installed correctly as a library). However, compiling the samples does not work.
I guess I have to somehow configure CMake to have “ocv_check_dependencies” - but how? I am lost!

Answer 1

Actually for OpenCV 2.4.4 beta the root CMakeList.txt file says:
OCV_OPTION(BUILD_EXAMPLES "Build all examples"
-DBUILD_EXAMPLES=ON worked just fine for me.

Answer 2

I got it.
In order to build the samples one has to change the default configuration for cmake by providing it via -D. What I did wrong was that I tried to execute cmake from within the samples directory.
The proper way to build the samples is invoking cmake like so (from within the root directory of the unpacked archive):
cmake -DBUILD_SAMPLES .
which will turn samples ON. One can proceed using make, make install than. The samples can be found in bin after building.
See also FAQ

Answer 3

How to compile OpenCV sample code ?
# For OpenCV 3
cd /path/to/opencv/samples/cpp/
#Compile
g++ -ggdb `pkg-config --cflags --libs opencv` facedetect.cpp -o facedetect
#run
./facedetect
Works for me.
googled from this link

Answer 4

mydragonisland's build instructions almost worked for me; with a minor reordering and including accents:
g++ facedetect.cpp -o facedetect `pkg-config --libs opencv`

Answer 5

The macro 'ocv_check_dependencies' is defined in: your_path_to/opencv/cmake/OpenCVModule.cmake
# ensures that all passed modules are available
# sets OCV_DEPENDENCIES_FOUND variable to TRUE/FALSE
macro(ocv_check_dependencies)
set(OCV_DEPENDENCIES_FOUND TRUE)
foreach(d ${ARGN})
if(d MATCHES "^opencv_[^ ]+$" AND NOT HAVE_${d})
set(OCV_DEPENDENCIES_FOUND FALSE)
break()
endif()
endforeach()
endmacro()
The top level CMakeLists.txt contains 'include' commands for files from opencv/cmake/ . Which is why the macro is available when you compile by calling cmake from the root of the opencv sources.

Answer 6

Reason
error message context:
CMake Error at CMakeLists.txt:10 (ocv_check_dependencies):
Unknown CMake command "ocv_check_dependencies".
This error message happens because cmake can't find the definition of ocv_check_dependencies
That's why the console said Unknown CMake command
Solution
If cmake cannot find where ocv_check_dependencies is defined
Just like #Nick Hockings Said:
ocv_check_dependencies is a macro defined in Your/OpenCV/path/OpenCVModule.cmake
macro(ocv_check_dependencies)
set(OCV_DEPENDENCIES_FOUND TRUE)
foreach(d ${ARGN})
if(d MATCHES "^opencv_[^ ]+$" AND NOT HAVE_${d})
set(OCV_DEPENDENCIES_FOUND FALSE)
break()
endif()
endforeach()
endmacro()
The fastest way is to copy this snippet above to your CMakeList.txt file right above where ocv_check_dependencies is
Therefore, cmake can finally understand what it is
That should do the trick, i hope no one else will bother with this question in the future

Answer 7

I got similar errors. My approach is as following:
1) cd xxx/samples 2) mkdir build 3) cd build 4) cmake .. 5) make
Now it works. We could not build individual project under their source files.

Answer 8

Following steps works for me.
Export toolchain path.
cd opencv-3.3.0/samples
cross_cmake &&
cross_make
cd opencv-3.3.0/samples/cpp/