SuperBuild: openjpeg missing png lib dependency

SuperBuild/CMake/External_openjpeg.cmake

@@ -14,16 +14,19 @@ else()
   message(STATUS "  Using OpenJPEG SuperBuild version")
   
   # declare dependencies
-  ADDTO_DEPENDENCIES_IF_NOT_SYSTEM(${proj} ZLIB TIFF)
+  ADDTO_DEPENDENCIES_IF_NOT_SYSTEM(${proj} ZLIB TIFF PNG)
 
   INCLUDE_SUPERBUILD_DEPENDENCIES(${${proj}_DEPENDENCIES})
   # set proj back to its original value
   set(proj OPENJPEG)
-  
+
   ADD_SUPERBUILD_CMAKE_VAR(TIFF_INCLUDE_DIR)
   ADD_SUPERBUILD_CMAKE_VAR(TIFF_LIBRARY)
   ADD_SUPERBUILD_CMAKE_VAR(ZLIB_INCLUDE_DIR)
   ADD_SUPERBUILD_CMAKE_VAR(ZLIB_LIBRARY)
+  ADD_SUPERBUILD_CMAKE_VAR(PNG_INCLUDE_DIR)
+  ADD_SUPERBUILD_CMAKE_VAR(PNG_LIBRARY)
+  
 
   if(MSVC)
   #TODO: add LCMS dependency