Try to use pkg-config to find external dependencies (fixes #324)

9 files changed, 642 insertions, 11 deletions

diff --git a/ChangeLog b/ChangeLog
index 57eeee97..1d9018df 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2019-06-22  Jay Berkenbilt  <ejb@ql.org>
 
+	* If pkg-config is available, use it to local libjpeg and zlib. If
+	not, fall back to old behavior. Fixes #324.
+
 	* The "make install" target explicitly sets a mode rather than
 	relying the user's umask. Fixes #326.
 
diff --git a/README-maintainer b/README-maintainer
index b00fac99..87c6f20a 100644
--- a/README-maintainer
+++ b/README-maintainer
@@ -121,6 +121,7 @@ RELEASE PREPARATION
     ```
     cp /usr/share/automake-1.11/install-sh .
     cp /usr/share/automake-1.11/mkinstalldirs .
+    cp /usr/share/aclocal/pkg.m4 m4
     ```
 
   The entire contents of the `m4` directory came from `libtool.m4`. If
diff --git a/aclocal.m4 b/aclocal.m4
index b408cfd0..1ffc46ab 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -18,3 +18,4 @@ m4_include([m4/ltoptions.m4])
 m4_include([m4/ltsugar.m4])
 m4_include([m4/ltversion.m4])
 m4_include([m4/lt~obsolete.m4])
+m4_include([m4/pkg.m4])
diff --git a/autofiles.sums b/autofiles.sums
index dead1791..e5002978 100644
--- a/autofiles.sums
+++ b/autofiles.sums
@@ -1,7 +1,10 @@
-5b50c329677bcc8c1d5a8b3654b79ccca8bbe80a452cc4bb14938370f316327a  configure.ac
+2784dbb5657cdd1ce359729771d8ad768becc3751dfac2b13b3eb11d146684a7  configure.ac
+9c264dc3fac489fd0178d3fa9fd29d5b0ccd37d561e926ef449fa01d99abded7  aclocal.m4
+79ee40c3867f4162a847c005a73a5e388e3882f71dd185d39d9ddf0312133086  libqpdf/qpdf/qpdf-config.h.in
 35bc5c645dc42d47f2daeea06f8f3e767c8a1aee6a35eb2b4854fd2ce66c3413  m4/ax_random_device.m4
 37f8897d5f68d7d484e5457832a8f190ddb7507fa2a467cb7ee2be40a4364643  m4/libtool.m4
 e77ebba8361b36f14b4d0927173a034b98c5d05049697a9ded84d85eb99a7990  m4/ltoptions.m4
 5a6735cda60e0ba0d1b706c0ef648f5d096298da46daefd9cdecdb6a0f4584d3  m4/ltsugar.m4
 a27b754709de61575197bf5a980696c98ae49da3f92f0de8ee7f42dd543b7465  m4/ltversion.m4
 26fa3285c35dd6ab00ed1e466ba92a17e4655e01897731ec18a587a4cf5e4f8d  m4/lt~obsolete.m4
+9fab676fae13feb97d5183a8ed86ae9398c76d21927c28bc59460d230f3e0884  m4/pkg.m4
diff --git a/autogen.sh b/autogen.sh
index cdb98e48..f3110800 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -3,4 +3,4 @@ set -e
 aclocal -I m4
 autoheader
 autoconf
-sha256sum configure.ac m4/* >| autofiles.sums
+sha256sum configure.ac aclocal.m4 libqpdf/qpdf/qpdf-config.h.in m4/* >| autofiles.sums
diff --git a/configure b/configure
index 0cd1b0be..495bdc59 100755
--- a/configure
+++ b/configure
@@ -650,6 +650,13 @@ HAVE_LD_VERSION_SCRIPT
 QPDF_LARGE_FILE_TEST_PATH
 WINDOWS_WMAIN_LINK
 WINDOWS_WMAIN_COMPILE
+pc_libjpeg_LIBS
+pc_libjpeg_CFLAGS
+pc_zlib_LIBS
+pc_zlib_CFLAGS
+PKG_CONFIG_LIBDIR
+PKG_CONFIG_PATH
+PKG_CONFIG
 WINDOWS_WORDSIZE
 IS_32BIT
 RANDOM_DEVICE
@@ -791,7 +798,14 @@ CXXFLAGS
 CCC
 CPP
 LT_SYS_LIBRARY_PATH
-CXXCPP'
+CXXCPP
+PKG_CONFIG
+PKG_CONFIG_PATH
+PKG_CONFIG_LIBDIR
+pc_zlib_CFLAGS
+pc_zlib_LIBS
+pc_libjpeg_CFLAGS
+pc_libjpeg_LIBS'
 
 
 # Initialize some variables set by options.
@@ -1494,6 +1508,19 @@ Some influential environment variables:
   LT_SYS_LIBRARY_PATH
               User-defined run-time library search path.
   CXXCPP      C++ preprocessor
+  PKG_CONFIG  path to pkg-config utility
+  PKG_CONFIG_PATH
+              directories to add to pkg-config's search path
+  PKG_CONFIG_LIBDIR
+              path overriding pkg-config's built-in search path
+  pc_zlib_CFLAGS
+              C compiler flags for pc_zlib, overriding pkg-config
+  pc_zlib_LIBS
+              linker flags for pc_zlib, overriding pkg-config
+  pc_libjpeg_CFLAGS
+              C compiler flags for pc_libjpeg, overriding pkg-config
+  pc_libjpeg_LIBS
+              linker flags for pc_libjpeg, overriding pkg-config
 
 Use these variables to override the choices made by `configure' or to help
 it to find libraries and programs with nonstandard names/locations.
@@ -16118,8 +16145,279 @@ fi
 
 
 
+
+
+
+
+
+
+
+if test "x$ac_cv_env_PKG_CONFIG_set" != "xset"; then
+	if test -n "$ac_tool_prefix"; then
+  # Extract the first word of "${ac_tool_prefix}pkg-config", so it can be a program name with args.
+set dummy ${ac_tool_prefix}pkg-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_PKG_CONFIG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $PKG_CONFIG in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_PKG_CONFIG="$PKG_CONFIG" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+PKG_CONFIG=$ac_cv_path_PKG_CONFIG
+if test -n "$PKG_CONFIG"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PKG_CONFIG" >&5
+$as_echo "$PKG_CONFIG" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+fi
+if test -z "$ac_cv_path_PKG_CONFIG"; then
+  ac_pt_PKG_CONFIG=$PKG_CONFIG
+  # Extract the first word of "pkg-config", so it can be a program name with args.
+set dummy pkg-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_ac_pt_PKG_CONFIG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $ac_pt_PKG_CONFIG in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_ac_pt_PKG_CONFIG="$ac_pt_PKG_CONFIG" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_ac_pt_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+ac_pt_PKG_CONFIG=$ac_cv_path_ac_pt_PKG_CONFIG
+if test -n "$ac_pt_PKG_CONFIG"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_pt_PKG_CONFIG" >&5
+$as_echo "$ac_pt_PKG_CONFIG" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+  if test "x$ac_pt_PKG_CONFIG" = x; then
+    PKG_CONFIG=""
+  else
+    case $cross_compiling:$ac_tool_warned in
+yes:)
+{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
+$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
+ac_tool_warned=yes ;;
+esac
+    PKG_CONFIG=$ac_pt_PKG_CONFIG
+  fi
+else
+  PKG_CONFIG="$ac_cv_path_PKG_CONFIG"
+fi
+
+fi
+if test -n "$PKG_CONFIG"; then
+	_pkg_min_version=0.9.0
+	{ $as_echo "$as_me:${as_lineno-$LINENO}: checking pkg-config is at least version $_pkg_min_version" >&5
+$as_echo_n "checking pkg-config is at least version $_pkg_min_version... " >&6; }
+	if $PKG_CONFIG --atleast-pkgconfig-version $_pkg_min_version; then
+		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+	else
+		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+		PKG_CONFIG=""
+	fi
+fi
 if test "$BUILD_INTERNAL_LIBS" = "0"; then
-   ac_fn_c_check_header_mongrel "$LINENO" "zlib.h" "ac_cv_header_zlib_h" "$ac_includes_default"
+    if test "$PKG_CONFIG" != ""; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for pc_zlib" >&5
+$as_echo_n "checking for pc_zlib... " >&6; }
+
+if test -n "$pc_zlib_CFLAGS"; then
+    pkg_cv_pc_zlib_CFLAGS="$pc_zlib_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"zlib\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "zlib") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_pc_zlib_CFLAGS=`$PKG_CONFIG --cflags "zlib" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$pc_zlib_LIBS"; then
+    pkg_cv_pc_zlib_LIBS="$pc_zlib_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"zlib\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "zlib") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_pc_zlib_LIBS=`$PKG_CONFIG --libs "zlib" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+   	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        pc_zlib_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "zlib" 2>&1`
+        else
+	        pc_zlib_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "zlib" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$pc_zlib_PKG_ERRORS" >&5
+
+	:
+elif test $pkg_failed = untried; then
+     	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	:
+else
+	pc_zlib_CFLAGS=$pkg_cv_pc_zlib_CFLAGS
+	pc_zlib_LIBS=$pkg_cv_pc_zlib_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+	CFLAGS="$CFLAGS $pc_zlib_CFLAGS"
+          CXXFLAGS="$CXXFLAGS $pc_zlib_CXXFLAGS"
+          LIBS="$LIBS $pc_zlib_LIBS"
+
+fi
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for pc_libjpeg" >&5
+$as_echo_n "checking for pc_libjpeg... " >&6; }
+
+if test -n "$pc_libjpeg_CFLAGS"; then
+    pkg_cv_pc_libjpeg_CFLAGS="$pc_libjpeg_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libjpeg\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libjpeg") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_pc_libjpeg_CFLAGS=`$PKG_CONFIG --cflags "libjpeg" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$pc_libjpeg_LIBS"; then
+    pkg_cv_pc_libjpeg_LIBS="$pc_libjpeg_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libjpeg\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libjpeg") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_pc_libjpeg_LIBS=`$PKG_CONFIG --libs "libjpeg" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+   	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        pc_libjpeg_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libjpeg" 2>&1`
+        else
+	        pc_libjpeg_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libjpeg" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$pc_libjpeg_PKG_ERRORS" >&5
+
+	:
+elif test $pkg_failed = untried; then
+     	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	:
+else
+	pc_libjpeg_CFLAGS=$pkg_cv_pc_libjpeg_CFLAGS
+	pc_libjpeg_LIBS=$pkg_cv_pc_libjpeg_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+	CFLAGS="$CFLAGS $pc_libjpeg_CFLAGS"
+          CXXFLAGS="$CXXFLAGS $pc_libjpeg_CXXFLAGS"
+          LIBS="$LIBS $pc_libjpeg_LIBS"
+
+fi
+    fi
+    if test "$pc_zlib_LIBS" = ""; then
+        ac_fn_c_check_header_mongrel "$LINENO" "zlib.h" "ac_cv_header_zlib_h" "$ac_includes_default"
 if test "x$ac_cv_header_zlib_h" = xyes; then :
 
 else
@@ -16127,7 +16425,7 @@ else
 fi
 
 
-   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing deflate" >&5
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing deflate" >&5
 $as_echo_n "checking for library containing deflate... " >&6; }
 if ${ac_cv_search_deflate+:} false; then :
   $as_echo_n "(cached) " >&6
@@ -16185,7 +16483,9 @@ else
   MISSING_ZLIB=1; MISSING_ANY=1
 fi
 
-   ac_fn_c_check_header_mongrel "$LINENO" "jpeglib.h" "ac_cv_header_jpeglib_h" "$ac_includes_default"
+    fi
+    if test "$pc_libjpeg_LIBS" = ""; then
+        ac_fn_c_check_header_mongrel "$LINENO" "jpeglib.h" "ac_cv_header_jpeglib_h" "$ac_includes_default"
 if test "x$ac_cv_header_jpeglib_h" = xyes; then :
 
 else
@@ -16193,7 +16493,7 @@ else
 fi
 
 
-   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing jpeg_destroy" >&5
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing jpeg_destroy" >&5
 $as_echo_n "checking for library containing jpeg_destroy... " >&6; }
 if ${ac_cv_search_jpeg_destroy+:} false; then :
   $as_echo_n "(cached) " >&6
@@ -16251,6 +16551,18 @@ else
   MISSING_JPEG=1; MISSING_ANY=1
 fi
 
+    fi
+    if test "$LIBS" != ""; then
+        nLIBS=""
+        for x in $LIBS; do
+            if echo $x | grep -q '^-L'; then
+                LDFLAGS="$LDFLAGS $x"
+            else
+                nLIBS="$nLIBS $x"
+            fi
+            LIBS=$nLIBS
+        done
+    fi
 fi
 
 qpdf_USE_WMAIN=0
diff --git a/configure.ac b/configure.ac
index 9cb99184..be34700c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -163,11 +163,39 @@ fi
 AC_SUBST(IS_32BIT)
 AC_SUBST(WINDOWS_WORDSIZE)
 
+PKG_PROG_PKG_CONFIG
 if test "$BUILD_INTERNAL_LIBS" = "0"; then
-   AC_CHECK_HEADER(zlib.h,,[MISSING_ZLIB_H=1; MISSING_ANY=1])
-   AC_SEARCH_LIBS(deflate,z zlib,,[MISSING_ZLIB=1; MISSING_ANY=1])
-   AC_CHECK_HEADER(jpeglib.h,,[MISSING_JPEG_H=1; MISSING_ANY=1])
-   AC_SEARCH_LIBS(jpeg_destroy,jpeg,,[MISSING_JPEG=1; MISSING_ANY=1])
+    if test "$PKG_CONFIG" != ""; then
+       PKG_CHECK_MODULES([pc_zlib], [zlib],
+         [CFLAGS="$CFLAGS $pc_zlib_CFLAGS"
+          CXXFLAGS="$CXXFLAGS $pc_zlib_CXXFLAGS"
+          LIBS="$LIBS $pc_zlib_LIBS"
+         ], [:])
+       PKG_CHECK_MODULES([pc_libjpeg], [libjpeg],
+         [CFLAGS="$CFLAGS $pc_libjpeg_CFLAGS"
+          CXXFLAGS="$CXXFLAGS $pc_libjpeg_CXXFLAGS"
+          LIBS="$LIBS $pc_libjpeg_LIBS"
+         ],[:])
+    fi
+    if test "$pc_zlib_LIBS" = ""; then
+        AC_CHECK_HEADER(zlib.h,,[MISSING_ZLIB_H=1; MISSING_ANY=1])
+        AC_SEARCH_LIBS(deflate,z zlib,,[MISSING_ZLIB=1; MISSING_ANY=1])
+    fi
+    if test "$pc_libjpeg_LIBS" = ""; then
+        AC_CHECK_HEADER(jpeglib.h,,[MISSING_JPEG_H=1; MISSING_ANY=1])
+        AC_SEARCH_LIBS(jpeg_destroy,jpeg,,[MISSING_JPEG=1; MISSING_ANY=1])
+    fi
+    if test "$LIBS" != ""; then
+        nLIBS=""
+        for x in $LIBS; do
+            if echo $x | grep -q '^-L'; then
+                LDFLAGS="$LDFLAGS $x"
+            else
+                nLIBS="$nLIBS $x"
+            fi
+            LIBS=$nLIBS
+        done
+    fi
 fi
 
 qpdf_USE_WMAIN=0
diff --git a/m4/pkg.m4 b/m4/pkg.m4
new file mode 100644
index 00000000..82bea96e
--- /dev/null
+++ b/m4/pkg.m4
@@ -0,0 +1,275 @@
+dnl pkg.m4 - Macros to locate and utilise pkg-config.   -*- Autoconf -*-
+dnl serial 11 (pkg-config-0.29.1)
+dnl
+dnl Copyright © 2004 Scott James Remnant <scott@netsplit.com>.
+dnl Copyright © 2012-2015 Dan Nicholson <dbn.lists@gmail.com>
+dnl
+dnl This program is free software; you can redistribute it and/or modify
+dnl it under the terms of the GNU General Public License as published by
+dnl the Free Software Foundation; either version 2 of the License, or
+dnl (at your option) any later version.
+dnl
+dnl This program is distributed in the hope that it will be useful, but
+dnl WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+dnl General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU General Public License
+dnl along with this program; if not, write to the Free Software
+dnl Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+dnl 02111-1307, USA.
+dnl
+dnl As a special exception to the GNU General Public License, if you
+dnl distribute this file as part of a program that contains a
+dnl configuration script generated by Autoconf, you may include it under
+dnl the same distribution terms that you use for the rest of that
+dnl program.
+
+dnl PKG_PREREQ(MIN-VERSION)
+dnl -----------------------
+dnl Since: 0.29
+dnl
+dnl Verify that the version of the pkg-config macros are at least
+dnl MIN-VERSION. Unlike PKG_PROG_PKG_CONFIG, which checks the user's
+dnl installed version of pkg-config, this checks the developer's version
+dnl of pkg.m4 when generating configure.
+dnl
+dnl To ensure that this macro is defined, also add:
+dnl m4_ifndef([PKG_PREREQ],
+dnl     [m4_fatal([must install pkg-config 0.29 or later before running autoconf/autogen])])
+dnl
+dnl See the "Since" comment for each macro you use to see what version
+dnl of the macros you require.
+m4_defun([PKG_PREREQ],
+[m4_define([PKG_MACROS_VERSION], [0.29.1])
+m4_if(m4_version_compare(PKG_MACROS_VERSION, [$1]), -1,
+    [m4_fatal([pkg.m4 version $1 or higher is required but ]PKG_MACROS_VERSION[ found])])
+])dnl PKG_PREREQ
+
+dnl PKG_PROG_PKG_CONFIG([MIN-VERSION])
+dnl ----------------------------------
+dnl Since: 0.16
+dnl
+dnl Search for the pkg-config tool and set the PKG_CONFIG variable to
+dnl first found in the path. Checks that the version of pkg-config found
+dnl is at least MIN-VERSION. If MIN-VERSION is not specified, 0.9.0 is
+dnl used since that's the first version where most current features of
+dnl pkg-config existed.
+AC_DEFUN([PKG_PROG_PKG_CONFIG],
+[m4_pattern_forbid([^_?PKG_[A-Z_]+$])
+m4_pattern_allow([^PKG_CONFIG(_(PATH|LIBDIR|SYSROOT_DIR|ALLOW_SYSTEM_(CFLAGS|LIBS)))?$])
+m4_pattern_allow([^PKG_CONFIG_(DISABLE_UNINSTALLED|TOP_BUILD_DIR|DEBUG_SPEW)$])
+AC_ARG_VAR([PKG_CONFIG], [path to pkg-config utility])
+AC_ARG_VAR([PKG_CONFIG_PATH], [directories to add to pkg-config's search path])
+AC_ARG_VAR([PKG_CONFIG_LIBDIR], [path overriding pkg-config's built-in search path])
+
+if test "x$ac_cv_env_PKG_CONFIG_set" != "xset"; then
+	AC_PATH_TOOL([PKG_CONFIG], [pkg-config])
+fi
+if test -n "$PKG_CONFIG"; then
+	_pkg_min_version=m4_default([$1], [0.9.0])
+	AC_MSG_CHECKING([pkg-config is at least version $_pkg_min_version])
+	if $PKG_CONFIG --atleast-pkgconfig-version $_pkg_min_version; then
+		AC_MSG_RESULT([yes])
+	else
+		AC_MSG_RESULT([no])
+		PKG_CONFIG=""
+	fi
+fi[]dnl
+])dnl PKG_PROG_PKG_CONFIG
+
+dnl PKG_CHECK_EXISTS(MODULES, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
+dnl -------------------------------------------------------------------
+dnl Since: 0.18
+dnl
+dnl Check to see whether a particular set of modules exists. Similar to
+dnl PKG_CHECK_MODULES(), but does not set variables or print errors.
+dnl
+dnl Please remember that m4 expands AC_REQUIRE([PKG_PROG_PKG_CONFIG])
+dnl only at the first occurence in configure.ac, so if the first place
+dnl it's called might be skipped (such as if it is within an "if", you
+dnl have to call PKG_CHECK_EXISTS manually
+AC_DEFUN([PKG_CHECK_EXISTS],
+[AC_REQUIRE([PKG_PROG_PKG_CONFIG])dnl
+if test -n "$PKG_CONFIG" && \
+    AC_RUN_LOG([$PKG_CONFIG --exists --print-errors "$1"]); then
+  m4_default([$2], [:])
+m4_ifvaln([$3], [else
+  $3])dnl
+fi])
+
+dnl _PKG_CONFIG([VARIABLE], [COMMAND], [MODULES])
+dnl ---------------------------------------------
+dnl Internal wrapper calling pkg-config via PKG_CONFIG and setting
+dnl pkg_failed based on the result.
+m4_define([_PKG_CONFIG],
+[if test -n "$$1"; then
+    pkg_cv_[]$1="$$1"
+ elif test -n "$PKG_CONFIG"; then
+    PKG_CHECK_EXISTS([$3],
+                     [pkg_cv_[]$1=`$PKG_CONFIG --[]$2 "$3" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes ],
+		     [pkg_failed=yes])
+ else
+    pkg_failed=untried
+fi[]dnl
+])dnl _PKG_CONFIG
+
+dnl _PKG_SHORT_ERRORS_SUPPORTED
+dnl ---------------------------
+dnl Internal check to see if pkg-config supports short errors.
+AC_DEFUN([_PKG_SHORT_ERRORS_SUPPORTED],
+[AC_REQUIRE([PKG_PROG_PKG_CONFIG])
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi[]dnl
+])dnl _PKG_SHORT_ERRORS_SUPPORTED
+
+
+dnl PKG_CHECK_MODULES(VARIABLE-PREFIX, MODULES, [ACTION-IF-FOUND],
+dnl   [ACTION-IF-NOT-FOUND])
+dnl --------------------------------------------------------------
+dnl Since: 0.4.0
+dnl
+dnl Note that if there is a possibility the first call to
+dnl PKG_CHECK_MODULES might not happen, you should be sure to include an
+dnl explicit call to PKG_PROG_PKG_CONFIG in your configure.ac
+AC_DEFUN([PKG_CHECK_MODULES],
+[AC_REQUIRE([PKG_PROG_PKG_CONFIG])dnl
+AC_ARG_VAR([$1][_CFLAGS], [C compiler flags for $1, overriding pkg-config])dnl
+AC_ARG_VAR([$1][_LIBS], [linker flags for $1, overriding pkg-config])dnl
+
+pkg_failed=no
+AC_MSG_CHECKING([for $1])
+
+_PKG_CONFIG([$1][_CFLAGS], [cflags], [$2])
+_PKG_CONFIG([$1][_LIBS], [libs], [$2])
+
+m4_define([_PKG_TEXT], [Alternatively, you may set the environment variables $1[]_CFLAGS
+and $1[]_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.])
+
+if test $pkg_failed = yes; then
+   	AC_MSG_RESULT([no])
+        _PKG_SHORT_ERRORS_SUPPORTED
+        if test $_pkg_short_errors_supported = yes; then
+	        $1[]_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "$2" 2>&1`
+        else 
+	        $1[]_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "$2" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$$1[]_PKG_ERRORS" >&AS_MESSAGE_LOG_FD
+
+	m4_default([$4], [AC_MSG_ERROR(
+[Package requirements ($2) were not met:
+
+$$1_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+_PKG_TEXT])[]dnl
+        ])
+elif test $pkg_failed = untried; then
+     	AC_MSG_RESULT([no])
+	m4_default([$4], [AC_MSG_FAILURE(
+[The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+_PKG_TEXT
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.])[]dnl
+        ])
+else
+	$1[]_CFLAGS=$pkg_cv_[]$1[]_CFLAGS
+	$1[]_LIBS=$pkg_cv_[]$1[]_LIBS
+        AC_MSG_RESULT([yes])
+	$3
+fi[]dnl
+])dnl PKG_CHECK_MODULES
+
+
+dnl PKG_CHECK_MODULES_STATIC(VARIABLE-PREFIX, MODULES, [ACTION-IF-FOUND],
+dnl   [ACTION-IF-NOT-FOUND])
+dnl ---------------------------------------------------------------------
+dnl Since: 0.29
+dnl
+dnl Checks for existence of MODULES and gathers its build flags with
+dnl static libraries enabled. Sets VARIABLE-PREFIX_CFLAGS from --cflags
+dnl and VARIABLE-PREFIX_LIBS from --libs.
+dnl
+dnl Note that if there is a possibility the first call to
+dnl PKG_CHECK_MODULES_STATIC might not happen, you should be sure to
+dnl include an explicit call to PKG_PROG_PKG_CONFIG in your
+dnl configure.ac.
+AC_DEFUN([PKG_CHECK_MODULES_STATIC],
+[AC_REQUIRE([PKG_PROG_PKG_CONFIG])dnl
+_save_PKG_CONFIG=$PKG_CONFIG
+PKG_CONFIG="$PKG_CONFIG --static"
+PKG_CHECK_MODULES($@)
+PKG_CONFIG=$_save_PKG_CONFIG[]dnl
+])dnl PKG_CHECK_MODULES_STATIC
+
+
+dnl PKG_INSTALLDIR([DIRECTORY])
+dnl -------------------------
+dnl Since: 0.27
+dnl
+dnl Substitutes the variable pkgconfigdir as the location where a module
+dnl should install pkg-config .pc files. By default the directory is
+dnl $libdir/pkgconfig, but the default can be changed by passing
+dnl DIRECTORY. The user can override through the --with-pkgconfigdir
+dnl parameter.
+AC_DEFUN([PKG_INSTALLDIR],
+[m4_pushdef([pkg_default], [m4_default([$1], ['${libdir}/pkgconfig'])])
+m4_pushdef([pkg_description],
+    [pkg-config installation directory @<:@]pkg_default[@:>@])
+AC_ARG_WITH([pkgconfigdir],
+    [AS_HELP_STRING([--with-pkgconfigdir], pkg_description)],,
+    [with_pkgconfigdir=]pkg_default)
+AC_SUBST([pkgconfigdir], [$with_pkgconfigdir])
+m4_popdef([pkg_default])
+m4_popdef([pkg_description])
+])dnl PKG_INSTALLDIR
+
+
+dnl PKG_NOARCH_INSTALLDIR([DIRECTORY])
+dnl --------------------------------
+dnl Since: 0.27
+dnl
+dnl Substitutes the variable noarch_pkgconfigdir as the location where a
+dnl module should install arch-independent pkg-config .pc files. By
+dnl default the directory is $datadir/pkgconfig, but the default can be
+dnl changed by passing DIRECTORY. The user can override through the
+dnl --with-noarch-pkgconfigdir parameter.
+AC_DEFUN([PKG_NOARCH_INSTALLDIR],
+[m4_pushdef([pkg_default], [m4_default([$1], ['${datadir}/pkgconfig'])])
+m4_pushdef([pkg_description],
+    [pkg-config arch-independent installation directory @<:@]pkg_default[@:>@])
+AC_ARG_WITH([noarch-pkgconfigdir],
+    [AS_HELP_STRING([--with-noarch-pkgconfigdir], pkg_description)],,
+    [with_noarch_pkgconfigdir=]pkg_default)
+AC_SUBST([noarch_pkgconfigdir], [$with_noarch_pkgconfigdir])
+m4_popdef([pkg_default])
+m4_popdef([pkg_description])
+])dnl PKG_NOARCH_INSTALLDIR
+
+
+dnl PKG_CHECK_VAR(VARIABLE, MODULE, CONFIG-VARIABLE,
+dnl [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
+dnl -------------------------------------------
+dnl Since: 0.28
+dnl
+dnl Retrieves the value of the pkg-config variable for the given module.
+AC_DEFUN([PKG_CHECK_VAR],
+[AC_REQUIRE([PKG_PROG_PKG_CONFIG])dnl
+AC_ARG_VAR([$1], [value of $3 for $2, overriding pkg-config])dnl
+
+_PKG_CONFIG([$1], [variable="][$3]["], [$2])
+AS_VAR_COPY([$1], [pkg_cv_][$1])
+
+AS_VAR_IF([$1], [""], [$5], [$4])dnl
+])dnl PKG_CHECK_VAR
diff --git a/manual/qpdf-manual.xml b/manual/qpdf-manual.xml
index 58d5d366..10af2c9b 100644
--- a/manual/qpdf-manual.xml
+++ b/manual/qpdf-manual.xml
@@ -4378,6 +4378,14 @@ print "\n";
           some files but not others.
          </para>
         </listitem>
+        <listitem>
+         <para>
+          If <command>pkg-config</command> is available, use it to
+          locate <filename>libjpeg</filename> and
+          <filename>zlib</filename> dependencies, falling back on old
+          behavior if unsuccessful.
+         </para>
+        </listitem>
        </itemizedlist>
       </listitem>
       <listitem>