Skeleton for G4

cpdfcommand.ml

@@ -1,6 +1,6 @@
 (* cpdf command line tools *)
 let demo = false
-let agpl = true
+let agpl = false
 let major_version = 2
 let minor_version = 8
 let minor_minor_version = 1

cpdfimage.ml

@@ -856,7 +856,38 @@ let recompress_1bpp_ccitt_lossless ~pixel_threshold ~length_threshold pdf s dict
              if !debug_image_processing then Printf.printf "no size reduction\n%!"
     end
 
-let recompress_1bpp_ccittg4_lossless ~pixel_threshold ~length_threshold pdf s dict reference = ()
+let recompress_1bpp_ccittg4_lossless ~pixel_threshold ~length_threshold pdf s dict reference =
+  let old = !reference in
+  let restore () = reference := old in
+  let w = match Pdf.lookup_direct pdf "/Width" dict with Some (Pdf.Integer i) -> i | _ -> error "bad width" in
+  let h = match Pdf.lookup_direct pdf "/Height" dict with Some (Pdf.Integer i) -> i | _ -> error "bad height" in
+  if w * h < pixel_threshold then (if !debug_image_processing then Printf.printf "pixel threshold not met\n%!") else (* (but also, jbig2enc fails on tiny images) *)
+  let size = match Pdf.lookup_direct pdf "/Length" dict with Some (Pdf.Integer i) -> i | _ -> 0 in
+  if size < length_threshold then (if !debug_image_processing then Printf.printf "length threshold not met\n%!") else
+    begin
+      Pdfcodec.decode_pdfstream_until_unknown pdf s;
+      match Pdf.lookup_direct pdf "/Filter" (fst !reference) with
+      | Some x ->
+          if !debug_image_processing then Printf.printf "could not decode - skipping %s length %i\n%!" (Pdfwrite.string_of_pdf x) size;
+          restore ()
+      | None ->
+        let data = match s with Pdf.Stream {contents = _, Pdf.Got d} -> d | _ -> assert false in
+        let compressed = Pdfcodec.encode_ccitt w data in
+        let newsize = bytes_size compressed in
+          if newsize < size then
+            begin
+              if !debug_image_processing then Printf.printf "1bpp to CCITT G4 %i -> %i (%i%%)\n%!" size newsize (int_of_float (float newsize /. float size *. 100.));
+              reference :=
+                (Pdf.add_dict_entry
+                (Pdf.add_dict_entry
+                  (Pdf.add_dict_entry dict "/Length" (Pdf.Integer newsize))
+                   "/Filter"
+                   (Pdf.Name "/CCITTFaxDecode")) "/DecodeParms" (Pdf.Array [Pdf.Dictionary [("/K", Pdf.Integer ~-1); ("/Columns", Pdf.Integer w)]])),
+                Pdf.Got (compressed)
+            end
+           else
+             if !debug_image_processing then Printf.printf "no size reduction\n%!"
+    end
 
 let recompress_1bpp_jbig2_lossless ~pixel_threshold ~length_threshold ~path_to_jbig2enc pdf s dict reference =
   complain_jbig2enc path_to_jbig2enc;