How can I determine MAGICKCORE_QUANTUM_DEPTH and MAGICKCORE_HDRI_ENABLE during compilation?

Question

I have a library that interfaces against ImageMagick 6. During compilation I get the below compilation warnings (promoted to errors by me).

I am aware that explicitly defining these values during compilation using -DMAGICKCORE_QUANTUM_DEPTH=16 -DMAGICKCORE_HDRI_ENABLE=0 will solve the issue (on my specific installation), however, as I am writing my CMake configuration files to be as portable as I can make them, this feels way to brittle and I really hope there is a better way.

Which brings me back to my question: Is there a way to determine MAGICKCORE_HDRI_ENABLE and MAGICKCORE_QUANTUM_DEPTH using cmake, bash or similar for the specific version of the library I am linking against?

/usr/include/ImageMagick-6/magick/magick-config.h:29:3: error: #warning "you should set MAGICKCORE_QUANTUM_DEPTH to sensible default set it to configure time default" [-Werror=cpp]
 # warning "you should set MAGICKCORE_QUANTUM_DEPTH to sensible default set it to configure time default"
   ^
/usr/include/ImageMagick-6/magick/magick-config.h:30:3: error: #warning "this is an obsolete behavior please fix your makefile" [-Werror=cpp]
 # warning "this is an obsolete behavior please fix your makefile"
   ^
/usr/include/ImageMagick-6/magick/magick-config.h:52:3: error: #warning "you should set MAGICKCORE_HDRI_ENABLE to sensible default set it to configure time default" [-Werror=cpp]
 # warning "you should set MAGICKCORE_HDRI_ENABLE to sensible default set it to configure time default"
   ^
/usr/include/ImageMagick-6/magick/magick-config.h:53:3: error: #warning "this is an obsolete behavior please fix yours makefile" [-Werror=cpp]
 # warning "this is an obsolete behavior please fix yours makefile"
   ^
cc1plus: all warnings being treated as errors

Answer 1

While writing the question I came across an answer to this. I'll summarize it here as the other questions regarding this angle it slightly differently.

Imagemagick ships with an utility called Magick++-config on my installation (Ubuntu 16.04) I found this utility under /usr/lib/x86_64-linux-gnu/ImageMagick-6.8.9/bin-Q16/Magick++-config. Below is the cmake code snipped I ended up using to extract the relevant build options.

find_package(ImageMagick 6.7 COMPONENTS Magick++ MagickCore)
if(ImageMagick_FOUND)
    # Find Imagemagick Library directory
    get_filename_component(MAGICK_LIB_DIR ${ImageMagick_MagickCore_LIBRARY} DIRECTORY)
    # Find where Magick++-config lives
    file(GLOB_RECURSE MAGICK_CONFIG FOLLOW_SYMLINKS ${MAGICK_LIB_DIR}/Magick++-config)
    # Ask about CXX and lib flags/locations
    set(MAGICK_CONFIG ${MAGICK_CONFIG} CACHE string "Path to Magick++-config utility")
    execute_process(COMMAND "${MAGICK_CONFIG}" "--cxxflags" OUTPUT_VARIABLE MAGICK_CXX_FLAGS)
    execute_process(COMMAND "${MAGICK_CONFIG}" "--libs" OUTPUT_VARIABLE MAGICK_LD_FLAGS)
    # Add these to cache
    set(MAGICK_CXX_FLAGS "${MAGICK_CXX_FLAGS}" CACHE string "ImageMagick configuration specific compilation flags." )
    set(MAGICK_LD_FLAGS  "${MAGICK_LD_FLAGS}" CACHE string "ImageMagick configuration specific linking flags.")
    # Split into list:
    string(REGEX MATCHALL "([^\ ]+)" MAGICK_CXX_FLAGS "${MAGICK_CXX_FLAGS}")
    string(REGEX MATCHALL "([^\ ]+)" MAGICK_LD_FLAGS "${MAGICK_LD_FLAGS}")
    # Remove trailing whitespace (CMAKE warns about this)
    string(STRIP "${MAGICK_CXX_FLAGS}" MAGICK_CXX_FLAGS)
    string(STRIP "${MAGICK_LD_FLAGS}" MAGICK_LD_FLAGS)

    target_compile_options(<project> ${MAGICK_CXX_FLAGS})
    target_link_libraries(<project> ${MAGICK_LD_FLAGS})

endif(ImageMagick_FOUND)

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