From 2955a30c80deedc82192d68120eb09a7c804f5ee Mon Sep 17 00:00:00 2001
From: John Whitington <john@coherentgraphics.co.uk>
Date: Fri, 22 Dec 2023 16:12:19 +0000
Subject: [PATCH] Detecting 1bpp images for processing

---
 cpdfimage.ml  | 35 ++++++++++++++++++++++++++---------
 cpdfimage.mli |  2 +-
 2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/cpdfimage.ml b/cpdfimage.ml
index 27ee98e..fc42c66 100644
--- a/cpdfimage.ml
+++ b/cpdfimage.ml
@@ -483,7 +483,6 @@ let image_of_input fobj i =
     Pdfpage.add_root pageroot [] pdf
 
 (* NOTE: ./cpdf -convert convert -recrypt -process-images -lossless-to-jpeg 65 ~/repos/pdfs/PDFTests/main128fail.pdf -o out.pdf *)
-(* FIXME Make sure this process is ok for masks too - do we get them, is it allowed etc. *)
 (* FIXME Only do if quality < 100 *)
 (* FIXME Error when path_to_convert not defined *)
 (* FIXME Need the "is it smaller" check from Pdfcodec.encode here too? *)
@@ -581,24 +580,42 @@ let lossless_to_jpeg pdf ~qlossless ~path_to_convert s dict reference =
         Sys.remove out2
       end
   | colspace, bpc ->
-    (*let colspace = Pdf.lookup_direct pdf "/ColorSpace" dict in
+    let colspace = Pdf.lookup_direct pdf "/ColorSpace" dict in
     let colspace, bpc, filter = 
       (match colspace with None -> "none" | Some x -> Pdfwrite.string_of_pdf x),
       (match bpc with None -> "none" | Some x -> Pdfwrite.string_of_pdf x),
       (match Pdf.lookup_direct pdf "/Filter" dict with None -> "none" | Some x -> Pdfwrite.string_of_pdf x)
     in
-      print_string (Printf.sprintf "%s (%s) [%s]\n" colspace bpc filter);*)
+      print_string (Pdfwrite.string_of_pdf dict);
+      print_string (Printf.sprintf "%s (%s) [%s]\n" colspace bpc filter);
       () (* an image we cannot or do not handle *)
 
-let process pdf ~q ~qlossless ~path_to_convert =
+(* JPEG to JPEG: RGB and CMYK JPEGS *)
+(* Lossless to JPEG: 8bpp Grey, 8bpp RGB, 8bpp CMYK including separation add ICCBased colourspaces *)
+(* 1 bit: anything to CCITT; anything to JBIG2 lossless (no globals yet) *)
+let process ?q ?qlossless ?jbig2 pdf ~path_to_convert =
   let process_obj _ s =
     match s with
     | Pdf.Stream ({contents = dict, _} as reference) ->
-        begin match Pdf.lookup_direct pdf "/Subtype" dict, Pdf.lookup_direct pdf "/Filter" dict with
-        | Some (Pdf.Name "/Image"), Some (Pdf.Name "/DCTDecode" | Pdf.Array [Pdf.Name "/DCTDecode"]) ->
-            jpeg_to_jpeg pdf ~q ~path_to_convert s dict reference
-        | Some (Pdf.Name "/Image"), _ ->
-            lossless_to_jpeg pdf ~qlossless ~path_to_convert s dict reference
+        begin match
+          Pdf.lookup_direct pdf "/Subtype" dict,
+          Pdf.lookup_direct pdf "/Filter" dict,
+          Pdf.lookup_direct pdf "/BitsPerComponent" dict,
+          Pdf.lookup_direct pdf "/ImageMask" dict
+        with
+        | Some (Pdf.Name "/Image"), Some (Pdf.Name "/DCTDecode" | Pdf.Array [Pdf.Name "/DCTDecode"]), _, _ ->
+            begin match q with
+            | Some q -> jpeg_to_jpeg pdf ~q ~path_to_convert s dict reference
+            | None -> ()
+            end
+        | Some (Pdf.Name "/Image"), _, Some (Pdf.Integer 1), _
+        | Some (Pdf.Name "/Image"), _, _, Some (Pdf.Boolean true) ->
+            Printf.printf "1bpp\n"
+        | Some (Pdf.Name "/Image"), _, _, _ ->
+            begin match qlossless with
+            | Some qlossless -> lossless_to_jpeg pdf ~qlossless ~path_to_convert s dict reference
+            | None -> ()
+            end
         | _ -> () (* not an image *)
         end
     | _ -> () (* not a stream *)
diff --git a/cpdfimage.mli b/cpdfimage.mli
index 3c0eba4..f13707b 100644
--- a/cpdfimage.mli
+++ b/cpdfimage.mli
@@ -11,7 +11,7 @@ val image_resolution : Pdf.t -> int list -> float -> (int * string * int * int *
 (** List images in JSON format *)
 val images : Pdf.t -> int list -> Cpdfyojson.Safe.t
 
-val process : Pdf.t -> q:int -> qlossless:int -> path_to_convert:string -> unit
+val process : ?q:int -> ?qlossless:int -> ?jbig2:int -> Pdf.t -> path_to_convert:string -> unit
 
 (**/**)
 val image_of_input : (unit -> Pdfio.bytes -> Pdf.pdfobject * (int * Pdf.pdfobject) list) -> Pdfio.input -> Pdf.t