Add package 'unpaper'.

pkgs/tools/graphics/unpaper/default.nix

@@ -0,0 +1,20 @@
+{ stdenv, fetchurl, pkgconfig, libav, libxslt }:
+
+stdenv.mkDerivation rec {
+  name = "unpaper-${version}";
+  version = "6.1";
+
+  src = fetchurl {
+    url = "https://www.flameeyes.eu/files/${name}.tar.xz";
+    sha256 = "0c5rbkxbmy9k8vxjh4cv0bgnqd3wqc99yzw215vkyjslvbsq8z13";
+  };
+
+  buildInputs = [ pkgconfig libav libxslt ];
+
+  meta = with stdenv.lib; {
+    homepage = https://www.flameeyes.eu/projects/unpaper;
+    description = "Post-processing tool for scanned sheets of paper";
+    license = licenses.gpl2;
+    maintainers = [ maintainers.rycee ];
+  };
+}

pkgs/top-level/all-packages.nix

@@ -11069,6 +11069,8 @@ let
     enableX11 = config.unison.enableX11 or true;
   };
 
+  unpaper = callPackage ../tools/graphics/unpaper { };
+
   uucp = callPackage ../tools/misc/uucp { };
 
   uvccapture = callPackage ../applications/video/uvccapture { };