diff --git a/config/aclocal.m4 b/config/aclocal.m4
index 89b889f2..ec210361 100644
--- a/config/aclocal.m4
+++ b/config/aclocal.m4
@@ -5972,13 +5972,12 @@ dnl   #endif /* HAVE_LIBZ */
 dnl
 dnl @version $Id: aclocal.m4,v 1.7 2000/06/26 10:04:08 loic dead $
 dnl @author Loic Dachary <loic@senga.org>
+dnl with modifications by Andreas Huggel <ahuggel@gmx.net>
 dnl
-
 AC_DEFUN([CHECK_ZLIB],
 #
 # Handle user hints
 #
-
 [AC_MSG_CHECKING(if zlib is wanted)
 AC_ARG_WITH(zlib,
 [  --with-zlib=DIR root directory path of zlib installation [defaults to
@@ -5997,14 +5996,13 @@ then
 	ZLIB_HOME=/usr
 fi
 ])
-
 #
 # Locate zlib, if wanted
 #
 if test -n "${ZLIB_HOME}"
 then
 	ZLIB_OLD_LDFLAGS=$LDFLAGS
-	ZLIB_OLD_CPPFLAGS=$LDFLAGS
+	ZLIB_OLD_CPPFLAGS=$CPPFLAGS
 	#
 	# Adding /usr/lib or /usr/include to the flags/libs may
 	# hurt if using a compiler not installed in the standard 
@@ -6018,7 +6016,7 @@ then
         AC_LANG_SAVE
         AC_LANG_C
 	AC_CHECK_LIB(z, inflateEnd, [zlib_cv_libz=yes], [zlib_cv_libz=no])
-        AC_CHECK_HEADER(zlib.h, [zlib_cv_zlib_h=yes], [zlib_cvs_zlib_h=no])
+        AC_CHECK_HEADER(zlib.h, [zlib_cv_zlib_h=yes], [zlib_cv_zlib_h=no])
         AC_LANG_RESTORE
 	if test "$zlib_cv_libz" = "yes" -a "$zlib_cv_zlib_h" = "yes"
 	then
diff --git a/config/config.mk.in b/config/config.mk.in
index 672652fb..63a8ef17 100644
--- a/config/config.mk.in
+++ b/config/config.mk.in
@@ -51,10 +51,11 @@ endif
 CXXCPP = @CXXCPP@
 
 # Preprocessor flags
-CPPFLAGS = @CPPFLAGS@
+CPPFLAGS = -I. @CPPFLAGS@
 
-# Linker flags
+# Linker flags and libraries
 LDFLAGS = @LDFLAGS@
+LIBS = @LIBS@
 
 # Suffix of executables
 EXEEXT := @EXEEXT@
@@ -69,10 +70,14 @@ ifeq ($(GCC),yes)
 	CFLAGS += -Wall
 endif
 
+# **********************************************************************
+# Libraries and Functions
+HAVE_LIBZ = @HAVE_LIBZ@
+HAVE_TIMEGM = @HAVE_TIMEGM@
+
 # **********************************************************************
 # Advanced auto-dependency generation
 # http://make.paulandlesley.org/autodep.html
-
 DEP_TRACKING = @DEP_TRACKING@
 
 ifdef DEP_TRACKING
@@ -92,17 +97,6 @@ endif
 
 endif
 
-# **********************************************************************
-# Global includes, libraries and defines
-INCS = -I. 
-LIBS = @LIBS@
-DEFS = 
-
-# **********************************************************************
-# Libraries and Functions
-HAVE_LIBZ = @HAVE_LIBZ@
-HAVE_TIMEGM = @HAVE_TIMEGM@
-
 # **********************************************************************
 # Installation programs
 INSTALL_EXE = @INSTALL@
diff --git a/config/configure.ac b/config/configure.ac
index 50c4bc7d..14845817 100644
--- a/config/configure.ac
+++ b/config/configure.ac
@@ -21,7 +21,8 @@ AC_PROG_RANLIB
 AC_PROG_LIBTOOL
 
 # Checks for libraries.
-AC_CHECK_LIB(m, exp, , AC_MSG_ERROR([libm not found.]))
+AC_CHECK_LIBM()
+LIBS="$LIBS $LIBM"
 CHECK_ZLIB()
 AC_SUBST(HAVE_LIBZ,$HAVE_LIBZ)
 
diff --git a/config/exiv2.pc.in b/config/exiv2.pc.in
index 4dcce031..9570bd47 100644
--- a/config/exiv2.pc.in
+++ b/config/exiv2.pc.in
@@ -8,5 +8,5 @@ Description: Exif and IPTC metadata library and tools
 Version: @PACKAGE_VERSION@
 URL: http://www.exiv2.org
 Libs: -L${libdir} -lexiv2
-Libs.private: @LIBS@
+Libs.private: @LDFLAGS@ @LIBS@
 Cflags: -I${includedir}
diff --git a/src/Makefile b/src/Makefile
index d533d7e6..d998167f 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -136,11 +136,6 @@ MCSRC = utils.cpp
 # Library
 LIBRARY = libexiv2.la
 
-# ******************************************************************************
-# Defines, Includes and Libraries
-CXXDEFS = $(DEFS)
-CXXINCS = $(INCS)
-
 # ******************************************************************************
 # Initialisations
 SHELL = /bin/sh
@@ -193,8 +188,8 @@ POSTDEPEND = if test ! -d $(DEPDIR); then mkdir $(DEPDIR); fi; \
 endif
 
 # Compilation shortcuts
-COMPILE.cc = $(CXX) $(CXXFLAGS) $(CXXDEFS) $(CXXINCS) -c
-COMPILE.c = $(CC) $(CFLAGS) $(DEFS) $(INCS) -c
+COMPILE.cc = $(CXX) $(CXXFLAGS) $(CPPFLAGS) -c
+COMPILE.c = $(CC) $(CFLAGS) $(CPPFLAGS) -c
 # LINK.cc does not need $(LIBS), libtool's dark magic takes care of that
 LINK.cc = $(CXX) $(CXXFLAGS) $(LIBRARY) $(LDFLAGS) -rpath $(libdir)
 
@@ -222,7 +217,7 @@ $(sort $(BINOBJ) $(EXIV2OBJ) $(MCOBJ) path-test.o): %.o: %.cpp
 
 %.ii: %.cpp
 	set -e; \
-	$(CXXCPP) $(CPPFLAGS) $(CXXDEFS) $(CXXINCS) $< | sed '/^[ 	]*$$/d' > $@
+	$(CXXCPP) $(CPPFLAGS) $< | sed '/^[ 	]*$$/d' > $@
 
 # ******************************************************************************
 # Targets
diff --git a/src/pngimage.cpp b/src/pngimage.cpp
index a5d692e2..029b5f98 100644
--- a/src/pngimage.cpp
+++ b/src/pngimage.cpp
@@ -135,6 +135,18 @@ namespace Exiv2 {
         clearMetadata();
         PngChunk::decode(this, io_->mmap(), io_->size());
 
+        /*
+          Todo:
+
+          - readMetadata implements the loop over the chunks in the image and
+            makes decisions what to do. It reads only one chunk at a time
+            instead of the whole file.
+
+          - new class PngChunk, initialized with the memory of one chunk and 
+            has all the access methods required to determine the field, key, 
+            to access and decompress data etc.
+        */
+
     } // PngImage::readMetadata
 
     void PngImage::writeMetadata()