-PKG_PROG_PKG_CONFIG
-
-AC_ARG_ENABLE([lbximg],
- [AS_HELP_STRING([--enable-lbximg],
- [build the lbximg tool (requires libpng) [default=auto]])],
- [enable_lbximg=$enableval],
- [enable_lbximg=auto])
-
-have_libpng=no
-if test x"$enable_lbximg" = x"auto"; then
-DX_CHECK_LIBPNG([1.2], [have_libpng=yes], [have_libpng=no])
-fi
-if test x"$enable_lbximg" = x"yes"; then
-DX_CHECK_LIBPNG([1.2], [have_libpng=yes])
-fi
-AM_CONDITIONAL([BUILD_LBXIMG], [test x"$have_libpng" = x"yes"])
+
+m4_include([lib/gnulib.mk])
+
+AC_ARG_WITH([libpng],
+ [AS_HELP_STRING([--with-libpng],
+ [build support for PNG output using libpng. [default=auto]])],
+ [with_libpng=$withval],
+ [with_libpng=auto])
+
+AS_CASE([$with_libpng],
+ [no], [have_libpng=false],
+ [yes], [DX_CHECK_LIBPNG([1.5], [have_libpng=true])],
+ [DX_CHECK_LIBPNG([1.5], [have_libpng=true], [have_libpng=false])])
+
+AM_CONDITIONAL([HAVE_LIBPNG], [$have_libpng])
+AS_IF([$have_libpng], [AC_DEFINE([HAVE_LIBPNG], [1],
+ [Define to 1 if libpng support is available])])