ENH: also look in /usr/local/include/libpng (OpenBSD)

ENH: error out with FATAL_ERROR if REQUIRED was given but png hasn't been
found

Alex

Modules/FindPNG.cmake

@@ -12,10 +12,13 @@
 # PNG depends on Zlib
 INCLUDE(FindZLIB)
 
+SET(PNG_FOUND "NO")
+
 IF(ZLIB_FOUND)
   FIND_PATH(PNG_PNG_INCLUDE_DIR png.h
   /usr/local/include
   /usr/include
+  /usr/local/include/libpng             # OpenBSD
   )
 
   SET(PNG_NAMES ${PNG_NAMES} png libpng)
@@ -42,4 +45,14 @@ IF(ZLIB_FOUND)
 
 ENDIF(ZLIB_FOUND)
 
+IF (PNG_FOUND)
+  IF (NOT PNG_FIND_QUIETLY)
+    MESSAGE(STATUS "Found PNG: ${PNG_LIBRARY}")
+  ENDIF (NOT PNG_FIND_QUIETLY)
+ELSE (PNG_FOUND)
+  IF (PNG_FIND_REQUIRED)
+    MESSAGE(FATAL_ERROR "Could not find PNG library")
+  ENDIF (PNG_FIND_REQUIRED)
+ENDIF (PNG_FOUND)
+
 MARK_AS_ADVANCED(PNG_PNG_INCLUDE_DIR PNG_LIBRARY )