cmake HAVE_PNG examples

mapnik/mapnik CMakeLists.txt :310 

list(APPEND MAPNIK_COMPILE_DEFS HAVE_PNG)

Kitware/VTK ThirdParty/gl2ps/vtkgl2ps/CMakeLists.txt :22 

target_compile_definitions(gl2ps
  PRIVATE
    HAVE_ZLIB
    HAVE_PNG)