cpdf-source/cpdfaddtext.ml

(* Superimpose text, page numbers etc. *)
open Pdfutil
open Cpdferror

type color =
  Grey of float
| RGB of float * float * float
| CYMK of float * float * float * float

(* Process UTF8 text to charcodes, given a font. *)
let charcodes_of_utf8 font s =
  let extractor = Pdftext.charcode_extractor_of_font_real ~debug:false font in
  let codepoints = Pdftext.codepoints_of_utf8 s in
    let charcodes =
      option_map
        (fun codepoint ->
           match extractor codepoint with
           | Some cc -> Some cc
           | None -> Printf.eprintf "Warning: character not found in font for unicode codepoint 0x%X\n" codepoint; None)
        codepoints
    in
    implode (map char_of_int charcodes)

(* Get the width of some text in the given font *)
let width_of_text font text =
  match font with
  | Pdftext.SimpleFont {Pdftext.fontmetrics = Some fontmetrics} ->
       begin try
         fold_left ( +. ) 0. (map (fun c -> fontmetrics.(int_of_char c)) (explode text))
       with
         _ -> 0.
       end
  | _ -> 0.

let colour_op = function
  | RGB (r, g, b) -> Pdfops.Op_rg (r, g, b)
  | Grey g -> Pdfops.Op_g g
  | CYMK (c, y, m, k) -> Pdfops.Op_k (c, y, m, k)

let colour_op_stroke = function
  | RGB (r, g, b) -> Pdfops.Op_RG (r, g, b)
  | Grey g -> Pdfops.Op_G g
  | CYMK (c, y, m, k) -> Pdfops.Op_K (c, y, m, k)

let ops longest_w x y rotate hoffset voffset outline linewidth unique_fontname unique_extgstatename colour fontsize text =
  [Pdfops.Op_q;
  Pdfops.Op_BMC "/CPDFSTAMP";
   Pdfops.Op_cm
     (Pdftransform.matrix_of_transform
       [Pdftransform.Translate (x -. hoffset, y -. voffset);
        Pdftransform.Rotate ((0., 0.), rotate)]);
   Pdfops.Op_BT;
   ] @
   (if outline then [Pdfops.Op_w linewidth; Pdfops.Op_Tr 1] else [Pdfops.Op_Tr 0]) @
   [colour_op colour; colour_op_stroke colour]
   @
   (match unique_extgstatename with None -> [] | Some n -> [Pdfops.Op_gs n])
   @
   [Pdfops.Op_Tf (unique_fontname, fontsize);
   Pdfops.Op_Tj text;
   Pdfops.Op_ET;
   Pdfops.Op_EMC;
   Pdfops.Op_Q]

type justification = LeftJustify | CentreJustify | RightJustify

(* Find the h-offset for justification based on the longest width, the current
width, the justification and the position. *)
let find_justification_offsets longest_w w position j =
  let open Cpdfposition in
    match j with
    | LeftJustify ->
        begin match position with
        | TopLeft _ | Left _ | PosLeft _ | BottomLeft _ -> 0.
        | Top _ | PosCentre _ | Bottom _ | Centre -> (longest_w -. w) /. 2.
        | TopRight _ | BottomRight _ | PosRight _ | Right _ -> longest_w -. w
        | Diagonal -> 0.
        | ReverseDiagonal -> 0.
        end
    | RightJustify ->
        begin match position with
        | TopLeft _ | Left _ | PosLeft _ | BottomLeft _ -> ~-.(longest_w -. w)
        | Top _ | PosCentre _ | Bottom _ | Centre -> ~-.((longest_w -. w) /. 2.)
        | TopRight _ | BottomRight _ | PosRight _ | Right _ -> 0.
        | Diagonal -> 0.
        | ReverseDiagonal -> 0.
        end
    | CentreJustify ->
        begin match position with
        | TopLeft _ | Left _ | PosLeft _ | BottomLeft _ -> ~-.((longest_w -. w) /. 2.)
        | Top _ | PosCentre _ | Bottom _ | Centre -> 0.
        | TopRight _ | BottomRight _ | PosRight _ | Right _ -> (longest_w -. w) /. 2.
        | Diagonal -> 0.
        | ReverseDiagonal -> 0.
        end

(* Lex an integer from the table *)
let extract_num header s =
  match Pdfgenlex.lex_string (Hashtbl.find header s) with
    [Pdfgenlex.LexInt i] -> Pdf.Integer i
  | [Pdfgenlex.LexReal f] -> Pdf.Real f
  | _ -> raise (Failure ("extract_num: " ^ s))

let extract_fontbbox header s =
  let num = function
      Pdfgenlex.LexInt i -> Pdf.Integer i
    | Pdfgenlex.LexReal f -> Pdf.Real f
    | _ -> raise (Failure "extract_fontbbox")
  in
    match Pdfgenlex.lex_string (Hashtbl.find header s) with
      [a; b; c; d] -> [num a; num b; num c; num d] 
    | _ -> raise (Failure "extract_fontbbox")

let remove_slash s =
  match explode s with
   '/'::x -> implode x
  | _ -> raise (Failure "remove_slash")

let extract_widths chars_and_widths =
  let win_to_name = map (fun (x, y) -> (y, x)) Pdfglyphlist.name_to_win in
    map
      (fun x ->
          try
            let name = List.assoc x win_to_name in
              let width = List.assoc (remove_slash name) chars_and_widths in
                width
          with
            _ -> 0)
      (ilist 0 255)

(* For finding the height for URL links, we try to find the Cap Height for the
   font. For now, this will only work for built-in fonts. We fall back to using
   the font size alone if we cannot get the cap height. *)
let cap_height fontname =
  try
    let font = unopt (Pdftext.standard_font_of_name ("/" ^ fontname)) in
    let header, _, _, _ = Pdfstandard14.afm_data font in
      let capheight = try extract_num header "CapHeight" with _ -> Pdf.Integer 0 in
        Some (match capheight with Pdf.Integer i -> float_of_int i | Pdf.Real r -> r | _ -> 0.)
  with
    _ -> None

let rec string_of_encoding = function
  | Pdftext.StandardEncoding -> "StandardEncoding"
  | Pdftext.MacRomanEncoding -> "MacRomanEncoding"
  | Pdftext.WinAnsiEncoding -> "WinAnsiEncoding"
  | _ -> error "unknown encoding"

let make_font embed encoding fontname =
  let font = unopt (Pdftext.standard_font_of_name ("/" ^ fontname)) in
  let header, width_data, _, chars_and_widths = Pdfstandard14.afm_data font in
    let widths = extract_widths (list_of_hashtbl chars_and_widths) in
    let flags = Pdfstandard14.flags_of_standard_font font in
    let fontbbox = extract_fontbbox header "FontBBox" in
    let italicangle = extract_num header "ItalicAngle" in
    let ascent = try extract_num header "Ascender" with _ -> Pdf.Integer 0 in
    let descent = try extract_num header "Descender" with _ -> Pdf.Integer 0 in
    let capheight = try extract_num header "CapHeight" with _ -> Pdf.Integer 0 in
    let stemv = Pdfstandard14.stemv_of_standard_font font in
      let fontdescriptor =
        Pdf.Dictionary
          [("/Type", Pdf.Name "/FontDescriptor");
           ("/FontName", Pdf.Name ("/" ^ fontname));
           ("/Flags", Pdf.Integer flags);
           ("/FontBBox", Pdf.Array fontbbox);
           ("/ItalicAngle", italicangle);
           ("/Ascent", ascent);
           ("/Descent", descent);
           ("/CapHeight", capheight);
           ("/StemV", Pdf.Integer stemv)]
      in
        if embed then
          Pdf.Dictionary
            [("/Type", Pdf.Name "/Font");
             ("/Subtype", Pdf.Name "/Type1");
             ("/BaseFont", Pdf.Name ("/" ^ fontname));          
             ("/Encoding", Pdf.Name "/WinAnsiEncoding");
             ("/FirstChar", Pdf.Integer 0);
             ("/LastChar", Pdf.Integer 255);
             ("/Widths", Pdf.Array (map (fun x -> Pdf.Integer x) widths));
             ("/FontDescriptor", fontdescriptor)]
        else
          Pdf.Dictionary
            [("/Type", Pdf.Name "/Font");
             ("/Subtype", Pdf.Name "/Type1");
             ("/Encoding", Pdf.Name "/WinAnsiEncoding");
             ("/BaseFont", Pdf.Name ("/" ^ fontname))]

let extract_page_text only_fontsize pdf _ page =
  let text_extractor = ref None in
  let right_font_size = ref false in
    fold_left ( ^ ) ""
      (map
        (function
         | Pdfops.Op_Tf (fontname, fontsize) ->
             right_font_size :=
               begin match only_fontsize with
                 Some x -> x = fontsize
               | _ -> false
               end;
             let fontdict =
               match Pdf.lookup_direct pdf "/Font" page.Pdfpage.resources with
               | None -> raise (Pdf.PDFError "Missing /Font in text extraction")
               | Some d ->
                   match Pdf.lookup_direct pdf fontname d with
                   | None -> raise (Pdf.PDFError "Missing font in text extraction")
                   | Some d -> d
             in
               text_extractor := Some (Pdftext.text_extractor_of_font pdf fontdict);
               ""
         | Pdfops.Op_Tj text when !text_extractor <> None ->
             if not !right_font_size then
               ""
             else
               Pdftext.utf8_of_codepoints
                 (Pdftext.codepoints_of_text (unopt !text_extractor) text)
         | Pdfops.Op_TJ (Pdf.Array objs) when !text_extractor <> None ->
             if not !right_font_size then
               ""
             else
               fold_left ( ^ ) ""
                 (option_map
                    (function
                     | Pdf.String text ->
                         Some
                           (Pdftext.utf8_of_codepoints
                             (Pdftext.codepoints_of_text (unopt !text_extractor) text))
                     | _ -> None)
                    objs)
         | _ -> "")
        (Pdfops.parse_operators pdf page.Pdfpage.resources page.Pdfpage.content))

(* For each page, extract all the ops with text in them, and concatenate it all together *)
let extract_text extract_text_font_size pdf range =
  fold_left (fun x y -> x ^ (if x <> "" && y <> "" then "\n" else "") ^ y) ""
    (Cpdfpage.map_pages (extract_page_text extract_text_font_size pdf) pdf range)

let rec process_text time text m =
  match m with
  | [] -> Cpdfstrftime.strftime ~time text
  | (s, r)::t -> process_text time (string_replace_all_lazy s r text) t

(* Find any %URL, sub in the text and return the new text together with a list
   of ordered (line num, URL, startpos, endpos) data.
   This will be used after any other %Specials have been processed, so that the
   positions do not change. *)

(* text|url]abc -> text, url, abc *)
let extract_url line =
  let text, rest = cleavewhile (neq '|') line in
    if rest = [] then error "bad URL syntax in text" else
    let url, rest = cleavewhile (neq ']') (tl rest) in
      if rest = [] then error "bad URL syntax in text" else
      (text, url, tl rest)

(* multiple %URL[a|b] *)
let get_urls_line line =
  let line = explode line in
  let urls = ref [] in
  let pos = ref 0 in
  let outline = ref [] in
  let rec loop = function
    | '%'::'U'::'R'::'L'::'['::t ->
        let text, url, rest = extract_url t in
          outline := rev text @ !outline;
          urls := (implode url, !pos, !pos + length text)::!urls;
          pos += length text;
          loop rest
    | h::t ->
        outline := h::!outline;
        pos += 1;
        loop t
    | [] -> ()
  in
    loop line;
    (implode (rev !outline), rev !urls)

(* Return page label at pdf page num, or page number in arabic if no label *) 
let pagelabel pdf num =
  Pdfpagelabels.pagelabeltext_of_pagenumber
    num
    (Pdfpagelabels.complete (Pdfpagelabels.read pdf))

let addtext
  lines linewidth outline fast colour fontname encoding embed bates batespad fontsize
  (font : Pdftext.font option)
  fontpdfobj underneath position hoffset voffset text pages orientation cropbox opacity
  justification filename extract_text_font_size shift pdf
=
  let time = Cpdfstrftime.current_time () in
  let endpage = Pdfpage.endpage pdf in
  let replace_pairs pdf filename bates batespad num page =
      [
       "%PageDiv2", (fun () -> string_of_int ((num + 1) / 2));
       "%Page", (fun () -> string_of_int num);
       "%Roman", (fun () -> roman_upper num);
       "%roman", (fun () -> roman_lower num);
       "%filename", (fun () -> filename);
       "%Label", (fun () -> pagelabel pdf num);
       "%EndPage", (fun () -> string_of_int endpage);
       "%EndLabel", (fun () -> pagelabel pdf endpage);
       "%ExtractedText", (fun () -> extract_page_text extract_text_font_size pdf num page);
       "%Bates",
          (fun () ->
            (let numstring = string_of_int (bates + num - 1) in
             match batespad with
               None -> numstring
             | Some w ->
                 if String.length numstring >= w
                   then numstring
                   else implode (many '0' (w - String.length numstring)) ^ numstring))]
  in
  let shifts = Cpdfcoord.parse_coordinates pdf shift in
  let addtext_page num page =
    let shift_x, shift_y = List.nth shifts (num - 1) in
    let resources', unique_extgstatename =
      if opacity < 1.0 then
        let dict =
          match Pdf.lookup_direct pdf "/ExtGState" page.Pdfpage.resources with
          | Some d -> d
          | None -> Pdf.Dictionary []
        in
          let unique_extgstatename = Pdf.unique_key "gs" dict in
            let dict' =
              Pdf.add_dict_entry dict unique_extgstatename
                (Pdf.Dictionary [("/ca", Pdf.Real opacity); ("/CA", Pdf.Real opacity)])
            in
              Pdf.add_dict_entry page.Pdfpage.resources "/ExtGState" dict', Some unique_extgstatename
      else
        page.Pdfpage.resources, None
    in
      let fontdict =
        match Pdf.lookup_direct pdf "/Font" page.Pdfpage.resources with
        | None -> Pdf.Dictionary []
        | Some d -> d
      in
              let calc_textwidth text =
                match font with
                | Some (Pdftext.StandardFont (f, _)) ->
                    let rawwidth =
                      Pdfstandard14.textwidth false encoding f text
                    in
                      (float rawwidth *. fontsize) /. 1000.
                | Some font ->
                    let rawwidth = width_of_text font text in
                      (rawwidth *. fontsize) /. 1000.
                | None -> 
                    let font =
                      match Pdf.lookup_direct pdf "/Font" page.Pdfpage.resources with
                      | Some fontdict ->
                          begin match Pdf.lookup_direct pdf fontname fontdict with
                          | Some font -> font
                          | None ->
                             (* For each item in the fontdict, follow its value and find the basename. If it matches, return that font *)
                             let font = ref None in
                             iter
                               (fun (k, v) ->
                                  match Pdf.lookup_direct pdf "/BaseFont" v with
                                  | Some (Pdf.Name n) when n = fontname -> font := Some v
                                  | _ -> ())
                               (match fontdict with Pdf.Dictionary d -> d | _ -> []);
                             match !font with Some f -> f | None -> failwith (Printf.sprintf "addtext: font %s not found" fontname)
                          end
                      | _ -> failwith "addtext: font not found for width"
                    in
                      let rawwidth = width_of_text (Pdftext.read_font pdf font) text in
                        (rawwidth *. fontsize) /. 1000.
              in
        let unique_fontname = Pdf.unique_key "F" fontdict in
          let ops, urls, x, y, hoffset, voffset, text, joffset =
            let text = process_text time text (replace_pairs pdf filename bates batespad num page) in
            let text, urls = get_urls_line text in

                let expanded_lines =
                  map
                    (function text ->
                       process_text time text (replace_pairs pdf filename bates batespad num page))
                    lines
                in
                let expanded_lines = (* process URLs for justification too *)
                  map (fun line -> fst (get_urls_line line)) expanded_lines
                in
                let textwidth = calc_textwidth text
                and allwidths = map calc_textwidth expanded_lines in
                  let longest_w = last (sort compare allwidths) in
                  let joffset = find_justification_offsets longest_w textwidth position justification in
                  let mediabox =
                    if cropbox then
                      match Pdf.lookup_direct pdf "/CropBox" page.Pdfpage.rest with
                      | Some pdfobject -> Pdf.parse_rectangle pdf (Pdf.direct pdf pdfobject)
                      | None -> Pdf.parse_rectangle pdf page.Pdfpage.mediabox
                    else
                      Pdf.parse_rectangle pdf page.Pdfpage.mediabox
                  in
                    let x, y, rotate = Cpdfposition.calculate_position false textwidth mediabox position in
                      let hoffset, voffset =
                        if position = Diagonal || position = ReverseDiagonal
                          then -. (cos ((pi /. 2.) -. rotate) *. voffset), sin ((pi /. 2.) -. rotate) *. voffset
                          else hoffset, voffset 
                      in
                        match font with
                        | Some f ->
                            ops longest_w (x +. shift_x) (y +. shift_y) rotate (hoffset +. joffset) voffset outline linewidth
                            unique_fontname unique_extgstatename colour fontsize text,
                            urls, x, y, hoffset, voffset, text, joffset
                        | None ->
                            ops longest_w (x +. shift_x) (y +. shift_y) rotate (hoffset +. joffset) voffset outline linewidth
                            fontname None colour fontsize text,
                            urls, x, y, hoffset, voffset, text, joffset
          in
            let newresources =
              match font with
              | Some (Pdftext.StandardFont _) ->
                  let newfontdict =
                    Pdf.add_dict_entry fontdict unique_fontname (make_font embed encoding fontname)
                  in
                    Pdf.add_dict_entry resources' "/Font" newfontdict
              | Some f ->
                  let newfontdict =
                    Pdf.add_dict_entry fontdict unique_fontname fontpdfobj
                  in
                    Pdf.add_dict_entry resources' "/Font" newfontdict
              | None -> page.Pdfpage.resources
          in
            (* Build annotations from URL data (get_urls and some sense of metrics) *)
            let annot (minx, miny, maxx, maxy) url =
              Pdf.Dictionary
                [("/Subtype", Pdf.Name "/Link");
                 ("/Rect", Pdf.Array [Pdf.Real minx; Pdf.Real miny; Pdf.Real maxx; Pdf.Real maxy]);
                 ("/BS", Pdf.Dictionary [("/W", Pdf.Integer 0)]);
                 ("/A", Pdf.Dictionary [("/URI", Pdf.String url);
                                        ("/Type", Pdf.Name "/Action");
                                        ("/S", Pdf.Name "/URI")])]
            in
            let annots =
              let annot_coord text pos =
                let before = take (explode text) pos in
                  calc_textwidth (implode before)
              in
                map (fun (url, s, e) ->
                       let sx = annot_coord text s in
                       let ex = annot_coord text e in
                       let x, y = x -. hoffset -. joffset, y -. voffset in
                       let height =
                         match cap_height fontname with
                         | Some c -> (c *. fontsize) /. 1000.
                         | None -> fontsize
                       in
                         Pdf.Indirect (Pdf.addobj pdf (annot (x +. sx, y, x +. ex, y +. height) url))) urls
            in
            let newrest =
              if annots = [] then page.Pdfpage.rest else
                let existing =
                  match Pdf.lookup_direct pdf "/Annots" page.Pdfpage.rest with
                  | Some (Pdf.Array a) -> a
                  | _ -> []
                in
                  Pdf.add_dict_entry page.Pdfpage.rest "/Annots" (Pdf.Array (annots @ existing))
            in
            let page =
              {page with
                 Pdfpage.resources = newresources;
                 Pdfpage.rest = newrest}
            in
              if underneath
                then Pdfpage.prepend_operators pdf ops ~fast:fast page
                else Pdfpage.postpend_operators pdf ops ~fast:fast page
  in
    Cpdfpage.process_pages (Cpdfutil.ppstub addtext_page) pdf pages

(* Prev is a list of lists of characters *)
let split_at_newline t =
  let rec split_at_newline_inner prev = function
    | [] -> rev (map implode (map rev prev))
    | '\\'::'\\'::'n'::t -> split_at_newline_inner (('n'::'\\'::'\\'::hd prev)::tl prev) t
    | '\\'::'n'::t -> split_at_newline_inner ([]::prev) t
    | h::t -> split_at_newline_inner ((h::hd prev)::tl prev) t
  in
    split_at_newline_inner [[]] (explode t)

let rec unescape_chars prev = function
  | [] -> rev prev
  | '\\'::('0'..'7' as a)::('0'..'7' as b)::('0'..'7' as c)::t ->
       let chr = char_of_int (int_of_string ("0o" ^ implode [a;b;c])) in
         unescape_chars (chr::prev) t
  | '\\'::'\\'::t -> unescape_chars ('\\'::prev) t
  | '\\'::c::t when c <> 'n' -> unescape_chars (c::prev) t
  | h::t -> unescape_chars (h::prev) t

let unescape_string s =
  implode (unescape_chars [] (explode s))

let
  addtexts linewidth outline fast fontname (font : Pdftext.font option) embed bates batespad colour position linespacing
  fontsize underneath text pages orientation cropbox opacity justification
  midline topline filename extract_text_font_size shift ?(raw=false) pdf
=
  if pages = [] then error "addtexts: empty page range" else
  let realfontname = ref fontname in
  let fontpdfobj =
    match font with
    | Some (StandardFont (f, encoding)) ->
        make_font embed encoding (Pdftext.string_of_standard_font f)
    | Some f ->
        Pdf.Indirect (Pdftext.write_font pdf f)
    | None -> 
        let firstpage =
          List.nth (Pdfpage.pages_of_pagetree pdf) (hd pages - 1)
        in
        match Pdf.lookup_direct pdf "/Font" firstpage.Pdfpage.resources with
        | Some fontdict ->
            begin match Pdf.lookup_direct pdf fontname fontdict with
            | Some font -> font
            | _ ->
               (* For each item in the fontdict, follow its value and find the basename. If it matches, return that font *)
               let font = ref None in
               iter
                 (fun (k, v) ->
                    match Pdf.lookup_direct pdf "/BaseFont" v with
                    | Some (Pdf.Name n) when n = fontname ->
                        font := Some v; realfontname := k
                    | _ -> ())
                 (match fontdict with Pdf.Dictionary d -> d | _ -> []);
               match !font with Some f -> f | None -> failwith (Printf.sprintf "addtext: font %s not found" fontname)
            end
        | _ -> failwith "addtext: font dictionary not present"
  in
    (* 19th May 2022. Reversed the phase order (split first, then get charcodes. This allows \n in custom fonts. *)
    let lines = map unescape_string (split_at_newline text) in
    let lines = map (fun text -> if raw then text else charcodes_of_utf8 (Pdftext.read_font pdf fontpdfobj) text) lines in
      let pdf = ref pdf in
        let voffset =
          let open Cpdfposition in
          match position with
          | Bottom _ | BottomLeft _ | BottomRight _ ->
              ref (0. -. (linespacing *. fontsize *. (float (length lines) -. 1.)))
          | Left _ | Right _ ->
              (* Vertically align *)
              ref (0. -. (linespacing *. ((fontsize *. (float (length lines) -. 1.)) /. 2.)))
          | Diagonal | ReverseDiagonal ->
              (* Change so that the whole paragraph sits on the centre... *)
              ref (0. -. ((linespacing *. fontsize *. (float (length lines) -. 1.)) /. 2.))
          | _ -> ref 0.
        in
          if midline then
            begin match font with
              | Some (Pdftext.StandardFont (font, _)) ->
                  let baseline_adjustment =
                    (fontsize *. float (Pdfstandard14.baseline_adjustment font)) /. 1000.
                  in
                    voffset := !voffset +. baseline_adjustment
              | Some (Pdftext.SimpleFont {fontdescriptor = Some {capheight}})  ->
                  voffset := !voffset +. capheight /. 2.
              | _ ->
                  Printf.eprintf "Unable to find midline adjustment in this font\n"
            end
          else
          if topline then
            begin match font with
              | Some (Pdftext.StandardFont (font, _)) ->
                  let baseline_adjustment =
                    (fontsize *. float (Pdfstandard14.baseline_adjustment font) *. 2.0) /. 1000.
                  in
                    voffset := !voffset +. baseline_adjustment
              | Some (Pdftext.SimpleFont {fontdescriptor = Some {capheight}})  ->
                  voffset := !voffset +. capheight
              | _ ->
                  Printf.eprintf "Unable to find midline adjustment in this font\n"
            end;
          let encoding =
            match font with
            | Some (Pdftext.StandardFont (_, e)) -> e
            | Some (Pdftext.SimpleFont {encoding}) -> encoding
            | _ -> Pdftext.WinAnsiEncoding
          in
            iter
              (fun line ->
                 let voff, hoff = !voffset, 0. in
                   pdf :=
                     addtext lines linewidth outline fast colour !realfontname encoding
                     embed bates batespad fontsize font fontpdfobj underneath position hoff voff line
                     pages orientation cropbox opacity justification filename
                     extract_text_font_size shift
                     !pdf;
                   voffset := !voffset +. (linespacing *. fontsize))
              lines;
              !pdf

let removetext range pdf =
  (* Could fail on nesting, or other marked content inside our marked content.*)
  let rec remove_until_last_EMC level = function
    | [] -> []
    | Pdfops.Op_BMC "/CPDFSTAMP"::more ->
        remove_until_last_EMC (level + 1) more
    | Pdfops.Op_EMC::more ->
        if level = 1
          then more
          else remove_until_last_EMC (level - 1) more
    | _::more ->
        remove_until_last_EMC level more
  in
    let rec remove_stamps prev = function
      | [] -> rev prev
      | Pdfops.Op_BMC "/CPDFSTAMP"::more ->
          let rest = remove_until_last_EMC 1 more in
            remove_stamps prev rest
      | h::t -> remove_stamps (h::prev) t
    in
      let removetext_page _ page =
        {page with
           Pdfpage.content =
             let ops = Pdfops.parse_operators pdf page.Pdfpage.resources page.Pdfpage.content in
               [Pdfops.stream_of_ops (remove_stamps [] ops)]}
      in
        Cpdfpage.process_pages (Cpdfutil.ppstub removetext_page) pdf range

let addrectangle
  fast (w, h) colour outline linewidth opacity position relative_to_cropbox
  underneath range pdf
=
  let addrectangle_page _ page =
    let resources', unique_extgstatename =
      if opacity < 1.0 then
        let dict =
          match Pdf.lookup_direct pdf "/ExtGState" page.Pdfpage.resources with
          | Some d -> d
          | None -> Pdf.Dictionary []
        in
          let unique_extgstatename = Pdf.unique_key "gs" dict in
            let dict' =
              Pdf.add_dict_entry dict unique_extgstatename
                (Pdf.Dictionary [("/ca", Pdf.Real opacity); ("/CA", Pdf.Real opacity)])
            in
              Pdf.add_dict_entry page.Pdfpage.resources "/ExtGState" dict', Some unique_extgstatename
      else
        page.Pdfpage.resources, None
    in
    let mediabox =
      if relative_to_cropbox then
        match Pdf.lookup_direct pdf "/CropBox" page.Pdfpage.rest with
        | Some pdfobject -> Pdf.parse_rectangle pdf (Pdf.direct pdf pdfobject)
        | None -> Pdf.parse_rectangle pdf page.Pdfpage.mediabox
      else
        Pdf.parse_rectangle pdf page.Pdfpage.mediabox
    in
    let x, y, _ =
      Cpdfposition.calculate_position false w mediabox position
    in
    let x, y =
      match position with
        Cpdfposition.Top _ | Cpdfposition.TopLeft _ | Cpdfposition.TopRight _ -> (x, y -. h)
      | Cpdfposition.Centre | Cpdfposition.PosCentre _ -> (x, y -. (h /. 2.))
      | _ -> (x, y)
    in
    let ops =
      [
       Pdfops.Op_q;
       Pdfops.Op_BMC "/CPDFSTAMP";
       colour_op colour;
       colour_op_stroke colour;
      ]
      @
     (if outline then [Pdfops.Op_w linewidth] else [])
     @
     (match unique_extgstatename with None -> [] | Some n -> [Pdfops.Op_gs n])
     @
     [
       Pdfops.Op_re (x, y, w, h);
       (if outline then Pdfops.Op_s else Pdfops.Op_f);
       Pdfops.Op_EMC;
       Pdfops.Op_Q
      ]
    in
      let page = {page with Pdfpage.resources = resources'} in
        if underneath
          then Pdfpage.prepend_operators pdf ops ~fast:fast page
          else Pdfpage.postpend_operators pdf ops ~fast:fast page
  in
    Cpdfpage.process_pages (Cpdfutil.ppstub addrectangle_page) pdf range

let rec remove_all_text_ops pdf resources content =
  let is_textop = function
    Pdfops.Op_Tj _ | Pdfops.Op_' _ | Pdfops.Op_'' _ | Pdfops.Op_TJ _ -> true
  | _ -> false
  in
    let content' =
      let ops = Pdfops.parse_operators pdf resources content in
        Pdfops.stream_of_ops
          (option_map (function x -> if is_textop x then None else Some x) ops) 
    in
      [content']

let remove_all_text_page pdf p =
  let resources = p.Pdfpage.resources in
  let content = p.Pdfpage.content in
    Cpdfutil.process_xobjects pdf p remove_all_text_ops;
    {p with Pdfpage.content = remove_all_text_ops pdf resources content}, pdf

let remove_all_text range pdf =
  let pages = Pdfpage.pages_of_pagetree pdf in
    let pagenums = indx pages in
    let pdf = ref pdf in
    let pages' = ref [] in
      iter2 
        (fun p pagenum ->
          let p', pdf' =
            if mem pagenum range
              then remove_all_text_page !pdf p
              else p, !pdf
          in
            pdf := pdf';
            pages' =| p')
        pages
        pagenums;
      Pdfpage.change_pages true !pdf (rev !pages')