Compiling opencv samples: unknown cmake command ocv_check_dependencies

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/