set (EXTERNAL_ZLIB 1)
set (EXTERNAL_LIBPNG 1)

if (EXTERNAL_ZLIB)
    find_package(ZLIB)
    include_directories(${ZLIB_INCLUDE_DIR})
else (EXTERNAL_ZLIB)
    set (ZLIB_INSTALL NO)
    set (ZLIB_SHARED NO)
    add_subdirectory(zlib)
    set (ZLIB_INCLUDE_DIR ${CMAKE_SOURCE_DIR}/3rdparty/zlib)
    set (ZLIB_LIBRARY zlib_static)
endif (EXTERNAL_ZLIB)

if (EXTERNAL_LIBPNG)
    find_package(PNG)
    include_directories(${PNG_INCLUDE_DIR})
    add_definitions(-DPNG_USE_DLL)
else(EXTERNAL_LIBPNG)
    set (PNG_INSTALL NO)
    set (PNG_SHARED NO)
    set (PNG_NO_STDIO NO)
    set (PNG_TESTS NO)
    add_subdirectory(libpng)
    set (PNG_INCLUDE_DIR ${CMAKE_SOURCE_DIR}/3rdparty/libpng ${ZLIB_INCLUDE_DIR})
    set (PNG_LIBRARIES png12_static ${ZLIB_LIBRARY})
endif(EXTERNAL_LIBPNG)

