SuperBuild: use libpng from superbuild if zlib is

SuperBuild/CMake/External_qt4.cmake

@@ -24,11 +24,7 @@ if(NOT __EXTERNAL_QT4__)
     set(QT4_SB_CONFIG)
     #RK: building faling on mac. png include is in a macframework
     if(USE_SYSTEM_PNG)
-      #why this regex below? because when the "awesome" configure of QT4
-      #is run a ';' remaining part of semicolon is considered as next
-      # command!
-      STRING(REGEX REPLACE ";" " " _PNG_INCLUDE_DIR_ ${PNG_INCLUDE_DIR})
-      set(QT4_SB_CONFIG "-I ${_PNG_INCLUDE_DIR_}")
+      set(QT4_SB_CONFIG "-I ${PNG_PNG_INCLUDE_DIR}")
     endif()
 
     if(APPLE)

SuperBuild/CMakeLists.txt

@@ -137,6 +137,12 @@ else()
   set(QT4_DEFAULT OFF)
 endif()
 
+if(USE_SYSTEM_ZLIB)
+  set(PNG_DEFAULT ON)
+else()
+  set(PNG_DEFAULT OFF)
+endif()
+
 if(WIN32)
   set(OSSIM_DEFAULT ON)
 else()
@@ -148,7 +154,7 @@ endif()
 SETUP_SYSTEM_LIBRARY(PROJECT ZLIB DEFAULT ON)
 SETUP_SYSTEM_LIBRARY(PROJECT JPEG DEFAULT OFF)
 SETUP_SYSTEM_LIBRARY(PROJECT EXPAT DEFAULT OFF)
-SETUP_SYSTEM_LIBRARY(PROJECT PNG DEFAULT ON)
+SETUP_SYSTEM_LIBRARY(PROJECT PNG DEFAULT ${PNG_DEFAULT})
 SETUP_SYSTEM_LIBRARY(PROJECT TIFF DEFAULT OFF)
 SETUP_SYSTEM_LIBRARY(PROJECT PROJ DEFAULT OFF)
 SETUP_SYSTEM_LIBRARY(PROJECT GEOTIFF DEFAULT OFF)