CMake/Modules/FindPNG.cmake

# - Find the native PNG includes and library
#
# This module defines
#  PNG_INCLUDE_DIR, where to find png.h, etc.
#  PNG_LIBRARIES, the libraries to link against to use PNG.
#  PNG_DEFINITIONS - You should add_definitons(${PNG_DEFINITIONS}) before compiling code that includes png library files.
#  PNG_FOUND, If false, do not try to use PNG.
# also defined, but not for general use are
#  PNG_LIBRARY, where to find the PNG library.
# None of the above will be defined unles zlib can be found.
# PNG depends on Zlib


if(PNG_FIND_QUIETLY)
  set(_FIND_ZLIB_ARG QUIET)
endif(PNG_FIND_QUIETLY)
find_package(ZLIB ${_FIND_ZLIB_ARG})

if(ZLIB_FOUND)
  find_path(PNG_PNG_INCLUDE_DIR png.h
  /usr/local/include/libpng             # OpenBSD
  )

  set(PNG_NAMES ${PNG_NAMES} png libpng png12 libpng12)
  find_library(PNG_LIBRARY NAMES ${PNG_NAMES} )

  if (PNG_LIBRARY AND PNG_PNG_INCLUDE_DIR)
      # png.h includes zlib.h. Sigh.
      SET(PNG_INCLUDE_DIR ${PNG_PNG_INCLUDE_DIR} ${ZLIB_INCLUDE_DIR} )
      SET(PNG_LIBRARIES ${PNG_LIBRARY} ${ZLIB_LIBRARY})

      if (CYGWIN)
        if(BUILD_SHARED_LIBS)
           # No need to define PNG_USE_DLL here, because it's default for Cygwin.
        else(BUILD_SHARED_LIBS)
          SET (PNG_DEFINITIONS -DPNG_STATIC)
        endif(BUILD_SHARED_LIBS)
      endif (CYGWIN)

  endif (PNG_LIBRARY AND PNG_PNG_INCLUDE_DIR)

endif(ZLIB_FOUND)

# handle the QUIETLY and REQUIRED arguments and set PNG_FOUND to TRUE if
# all listed variables are TRUE
include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(PNG  DEFAULT_MSG  PNG_LIBRARY PNG_PNG_INCLUDE_DIR)

mark_as_advanced(PNG_PNG_INCLUDE_DIR PNG_LIBRARY )