cpdf-source/cpdfjson.ml

(* Read and write PDF files in JSON format.

The file is an array of arrays containing an object number followed by an
object, one for each object in the file and two special ones:

Object -1: CPDF's own data with the PDF version number, CPDF JSON format
number, and flags used when writing (which may be required when reading):

  o /CPDFJSONformatversion (CPDFJSON integer (see below), currently 2)
  o /CPDFJSONcontentparsed (boolean, true if content streams have been parsed)
  o /CPDFJSONstreamdataincluded (boolean, true if stream data included. Cannot
  round-trip if false).
  o /CPDFJSONmajorpdfversion (CPDFJSON integer)
  o /CPDFJSONminorpdfversion (CPDFJSON integer)

Object 0: The PDF's trailer dictionary

Objects 1..n: The PDF's objects.

  o PDF arrays, dictionaries, booleans, and strings are the same in JSON.
  o Integers are written as {"I": 0}
  o Floats are written as {"F": 0.0}
  o Names are written as {"N": "/Pages"}
  o Indirect references are integers
  o Streams are {"S": [dict, data]}

  o Strings are converted from PDFDocEncoding to UTF8 before being encoded in
  JSON. When they are read back the process is JSON encoded --> UTF8 -->
  PDFDocEncoding. This process is to allow easier editing of strings. This
  does not happen to strings within text operators in parsed content streams. 

There are two subformats: parsing content streams or not.  Hello World in CPDF
JSON without parsing content streams:

[
  [
  -1, { "/CPDFJSONformatversion": { "I": 2 },
  "/CPDFJSONcontentparsed": false, "/CPDFJSONstreamdataincluded": true,
  "/CPDFJSONmajorpdfversion": { "I": 1 },
  "/CPDFJSONminorpdfversion": { "I": 1 } } ], [
  0, { "/Size": { "I": 4 }, "/Root": 4,
  "/ID": [ "èÎ25\u001e³/°q:Oʇ°u‰", "èÎ25\u001e³/°q:Oʇ°u‰" ] } ], [
  1, { "/Type": { "N": "/Pages" }, "/Kids": [ 3 ], "/Count": { "I": 1 } } ],
  [
  2, {
  "S": [
    { "/Length": { "I": 49 } },
    "1 0 0 1 50 770 cm BT/F0 36 Tf(Hello, World!)Tj ET"
  ] } ], [
  3, { "/Type": { "N": "/Page" }, "/Parent": 1,
  "/Resources": {
    "/Font": {
      "/F0": {
        "/Type": { "N": "/Font" },
        "/Subtype": { "N": "/Type1" },
        "/BaseFont": { "N": "/Times-Italic" }
      }
    }
  },
  "/MediaBox": [
    { "I": 0 }, { "I": 0 }, { "F": 595.2755905510001 }, { "F": 841.88976378 }
  ], "/Rotate": { "I": 0 }, "/Contents": [ 2 ] } ], [
  4, { "/Type": { "N": "/Catalog" }, "/Pages": 1 } ]
]

Alternative object number 2 when parsing of object streams in operation:

2, {
"S": [
  {}, [
  [
  { "F": 1.0 }, { "F": 0.0 }, { "F": 0.0 }, { "F": 1.0 }, { "F": 50.0 }, {
  "F": 770.0 }, "cm" ], [ "BT" ], [ "/F0", { "F": 36.0 }, "Tf" ], [
  "Hello, World!", "Tj" ], [ "ET" ] ]
] } ], [

When parsing content streams:

  o Each operation is an array
  o The 'operation' for inline images is "InlineImage"

CPDF currently never preserves object streams, and only outputs unencrypted files.

When reloading a JSON file, CPDF knows how to correct /Length entries in
streams, so you need not worry about them.  *)

open Pdfutil
open Cpdferror

module J = Cpdfyojson.Safe
module P = Pdf
module O = Pdfops

let opf = function
  | `Assoc ["F", `Float f] -> f
  | `Assoc ["F", `Int i] -> float_of_int i
  | _ -> error "num: not a float"

let opi = function
  | `Assoc ["I", `Int i] -> i
  | `Assoc ["I", `Float f] -> int_of_float f
  | _ -> error "num: not an integer"

let rec op_of_json = function
  | `List [`String "S"] -> O.Op_S
  | `List [`String "s"] -> O.Op_s
  | `List [`String "f"] -> O.Op_f
  | `List [`String "F"] -> O.Op_F
  | `List [`String "f*"] -> O.Op_f'
  | `List [`String "B"] -> O.Op_B
  | `List [`String "B*"] -> O.Op_B'
  | `List [`String "b"] -> O.Op_b
  | `List [`String "b*"] -> O.Op_b'
  | `List [`String "n"] -> O.Op_n
  | `List [`String "W"] -> O.Op_W
  | `List [`String "W*"] -> O.Op_W'
  | `List [`String "BT"] -> O.Op_BT
  | `List [`String "ET"] -> O.Op_ET
  | `List [`String "q"] -> O.Op_q
  | `List [`String "Q"] -> O.Op_Q
  | `List [`String "h"] -> O.Op_h
  | `List [`String "T*"] -> O.Op_T'
  | `List [`String "EMC"] -> O.Op_EMC
  | `List [`String "BX"] -> O.Op_BX
  | `List [`String "EX"] -> O.Op_EX
  | `List [a; b; c; d; `String "re"] -> O.Op_re (opf a, opf b, opf c, opf d)
  | `List [a; b; c; d; `String "k"] -> O.Op_k (opf a, opf b, opf c, opf d)
  | `List [a; b; `String "m"] -> O.Op_m (opf a, opf b)
  | `List [a; b; `String "l"] -> O.Op_l (opf a, opf b)
  | `List [`String s; obj; `String "BDC"] -> O.Op_BDC (s, object_of_json obj)
  | `List [`String s; `String "gs"] -> O.Op_gs s
  | `List [`String s; `String "Do"] -> O.Op_Do s
  | `List [`String s; `String "CS"] -> O.Op_CS s
  | `List [i; `String "j"] -> O.Op_j (opi i)
  | `List [a; b; c; d; e; f; `String "cm"] ->
      O.Op_cm
        {Pdftransform.a = opf a; Pdftransform.b = opf b; Pdftransform.c = opf c;
         Pdftransform.d = opf d; Pdftransform.e = opf e; Pdftransform.f = opf f}
  | `List [`List fls; y; `String "d"] -> O.Op_d (map opf fls, opf y)
  | `List [a; `String "w"] -> O.Op_w (opf a)
  | `List [a; `String "J"] -> O.Op_J (opi a)
  | `List [a; `String "M"] -> O.Op_M (opf a)
  | `List [`String s; `String "ri"] -> O.Op_ri s
  | `List [a; `String "i"] -> O.Op_i (opi a)
  | `List [a; b; c; d; e; f; `String "c"] -> O.Op_c (opf a, opf b, opf c, opf d, opf e, opf f)
  | `List [a; b; c; d; `String "v"] -> O.Op_v (opf a, opf b, opf c, opf d)
  | `List [a; b; c; d; `String "y"] -> O.Op_y (opf a, opf b, opf c, opf d)
  | `List [a; `String "Tc"] -> O.Op_Tc (opf a)
  | `List [a; `String "Tw"] -> O.Op_Tw (opf a)
  | `List [a; `String "Tz"] -> O.Op_Tz (opf a)
  | `List [a; `String "TL"] -> O.Op_TL (opf a)
  | `List [`String k; n; `String "Tf"] -> O.Op_Tf (k, opf n)
  | `List [a; `String "Tr"] -> O.Op_Tr (opi a)
  | `List [a; `String "Ts"] -> O.Op_Ts (opf a)
  | `List [a; b; `String "Td"] -> O.Op_Td (opf a, opf b)
  | `List [a; b; `String "TD"] -> O.Op_TD (opf a, opf b)
  | `List [a; b; c; d; e; f; `String "Tm"] ->
        O.Op_Tm
          {Pdftransform.a = opf a; Pdftransform.b = opf b; Pdftransform.c = opf c;
           Pdftransform.d = opf d; Pdftransform.e = opf e; Pdftransform.f = opf f}
  | `List [`String s; `String "Tj"] -> Op_Tj s
  | `List [obj; `String "TJ"] -> Op_TJ (object_of_json obj)
  | `List [`String s; `String "'"] -> Op_' s
  | `List [a; b; `String s; `String "''"] -> Op_'' (opf a, opf b, s)
  | `List [a; b; `String "d0"] -> Op_d0 (opf a, opf b)
  | `List [a; b; c; d; e; f; `String "d1"] -> Op_d1 (opf a, opf b, opf c, opf d, opf e, opf f)
  | `List [`String s; `String "cs"] -> Op_cs s 
  | `List [a; `String "G"] -> Op_G (opf a);
  | `List [a; `String "g"] -> Op_g (opf a);
  | `List [a; b; c; `String "RG"] -> Op_RG (opf a, opf b, opf c);
  | `List [a; b; c; `String "rg"] -> Op_rg (opf a, opf b, opf c);
  | `List [a; b; c; d; `String "K"] -> Op_K (opf a, opf b, opf c, opf d);
  | `List [`String s; `String "sh"] -> Op_sh s;
  | `List [`String s; `String "MP"] -> Op_MP s;
  | `List [`String s; `String "BMC"] -> Op_BMC s;
  | `List [`String s; `String "Unknown"] -> O.Op_Unknown s
  | `List [`String s; obj; `String "DP"] -> O.Op_DP (s, object_of_json obj)
  | `List [a; `String b; `String "InlineImage"] ->
      O.InlineImage (object_of_json a, Pdfio.bytes_of_string b)
  | `List torev ->
      begin match rev torev with
      | `String "SCN"::ns -> O.Op_SCN (map opf (rev ns))
      | `String "SC"::ns -> O.Op_SC (map opf (rev ns))
      | `String "sc"::ns -> O.Op_sc (map opf (rev ns))
      | `String "scn"::ns -> O.Op_scn (map opf (rev ns))
      | `String "SCNName"::`String s::ns -> O.Op_SCNName (s, map opf (rev ns))
      | `String "scnName"::`String s::ns -> O.Op_scnName (s, map opf (rev ns))
      | j ->
          Printf.eprintf "Unable to read reversed op from %s\n" (J.show (`List j));
          error "op reading failed"
      end
  | j ->
      Printf.eprintf "Unable to read op from %s\n" (J.show j);
      error "op reading failed"

and object_of_json = function
  | `Null -> P.Null
  | `Bool b -> P.Boolean b
  | `Int n -> Pdf.Indirect n
  | `String s -> P.String s
  | `List objs -> P.Array (map object_of_json objs)
  | `Assoc ["I", `Int i] -> P.Integer i
  | `Assoc ["F", `Float f] -> P.Real f
  | `Assoc ["N", `String n] -> P.Name n
  | `Assoc ["S", `List [dict; `String data]] ->
      let d' =
        P.add_dict_entry (object_of_json dict) "/Length" (P.Integer (String.length data))
      in
        P.Stream (ref (d', P.Got (Pdfio.bytes_of_string data)))
  | `Assoc ["S", `List [dict; `List parsed_ops]] ->
      begin match 
        Pdfops.stream_of_ops (List.map op_of_json parsed_ops)
      with
        | P.Stream {contents = (_, Pdf.Got data)} ->
            let d' =
              P.add_dict_entry (object_of_json dict) "/Length" (P.Integer (Pdfio.bytes_size data))
            in
              P.Stream (ref (d', Pdf.Got data))
        | _ -> assert false
      end
  | `Assoc elts -> P.Dictionary (map (fun (n, o) -> (n, object_of_json o)) elts)
  | _ -> error "not recognised in object_of_json"

let pdf_of_json json =
  let objs = match json with `List objs -> objs | _ -> error "bad json top level" in
  let params = ref Pdf.Null in
  let trailerdict = ref Pdf.Null in
    let objects =
      option_map
        (function
         | `List [`Int objnum; o] ->
             begin match objnum with
             | -1 -> params := object_of_json o; None 
             | 0 -> trailerdict := object_of_json o; None
             | n when n < 0 -> None
             | n ->  Some (n, object_of_json o)
             end
         | _ -> error "json bad obj")
        objs
    in
  begin match Pdf.lookup_direct (Pdf.empty ()) "/CPDFJSONstreamdataincluded" !params with
  | Some (Pdf.Boolean false) -> error "no stream data; cannot reconstruct PDF" 
  | _ -> ()  
  end;
  let major =
    match Pdf.lookup_direct (Pdf.empty ()) "/CPDFJSONmajorpdfversion" !params with 
      Some (Pdf.Integer i) -> i | _ -> error "bad major version"
  in
  let minor =
    match Pdf.lookup_direct (Pdf.empty ()) "/CPDFJSONminorpdfversion" !params with 
      Some (Pdf.Integer i) -> i | _ -> error "bad minor version"
  in
  let root =
    match !trailerdict with Pdf.Dictionary d ->
      begin match lookup "/Root" d with
        Some (Pdf.Indirect i) -> i | _ -> error "bad root"
      end
    | _ -> error "bad root 2"
  in
  let objmap = P.pdfobjmap_empty () in
    List.iter (fun (k, v) -> Hashtbl.add objmap k (ref (P.Parsed v), 0)) objects;
    let objects =
      {P.maxobjnum = 0;
       P.parse = None;
       P.pdfobjects = objmap;
       P.object_stream_ids = Hashtbl.create 0}
    in
      {P.major;
       P.minor;
       P.root;
       P.objects;
       P.trailerdict = !trailerdict;
       P.was_linearized = false;
       P.saved_encryption = None}

let mkfloat f = `Assoc [("F", `Float f)]
let mkint i = `Assoc [("I", `Int i)]
let mkname n = `Assoc [("N", `String n)]

let rec json_of_object pdf fcs no_stream_data pcs = function
  | P.Null -> `Null
  | P.Boolean b -> `Bool b
  | P.Integer i -> mkint i
  | P.Real r -> mkfloat r
  | P.String s -> `String s
  | P.Name n -> mkname n
  | P.Array objs -> `List (map (json_of_object pdf fcs no_stream_data pcs) objs)
  | P.Dictionary elts ->
      iter
        (function
            ("/Contents", P.Indirect i) ->
               begin match Pdf.lookup_obj pdf i with
               | Pdf.Array is -> iter (function Pdf.Indirect i -> fcs i | _ -> ()) is
               | _ -> fcs i
               end
          | ("/Contents", P.Array elts) -> iter (function P.Indirect i -> fcs i | _ -> ()) elts
          | _ -> ())
        elts;
      `Assoc (map (fun (k, v) -> (k, json_of_object pdf fcs no_stream_data pcs v)) elts)
  | P.Stream ({contents = (P.Dictionary dict as d, stream)} as mut) as thestream ->
      P.getstream thestream;
      let str, dict' =
        match P.lookup_direct pdf "/FunctionType" d, pcs with
        | Some _, true ->
            Pdfcodec.decode_pdfstream_until_unknown pdf thestream;
            let dict = P.remove_dict_entry d "/Filter" in
              begin match !mut with (_, P.Got b) -> (Pdfio.string_of_bytes b, dict) | _ -> error "/FunctionType: failure: decomp" end
        | _ ->
            if no_stream_data then ("<<stream data elided>>", d) else
              match !mut with (_, P.Got b) -> (Pdfio.string_of_bytes b, d) | _ -> error "failure: toget"
      in
        json_of_object pdf fcs no_stream_data pcs (P.Dictionary [("S", P.Array [dict'; P.String str])])
  | P.Stream _ -> error "error: stream with not-a-dictionary"
  | P.Indirect i ->
      begin match P.lookup_obj pdf i with
      | P.Stream {contents = (P.Dictionary dict as d, _)} ->
          begin match P.lookup_direct pdf "/Subtype" d with
          | Some (P.Name "/Form") -> fcs i
          | _ ->
              begin match P.lookup_direct pdf "/Type" d with
              | Some (P.Name "/Pattern") -> fcs i
              | _ -> ()
              end
          end
      | _ -> ()
      end;
      `Int i

let json_of_op pdf no_stream_data = function
  | O.Op_S -> `List [`String "S"]
  | O.Op_s -> `List [`String "s"]
  | O.Op_f -> `List [`String "f"]
  | O.Op_F -> `List [`String "F"]
  | O.Op_f' ->`List [`String "f*"]
  | O.Op_B -> `List [`String "B"]
  | O.Op_B' -> `List [`String "B*"]
  | O.Op_b -> `List [`String "b"]
  | O.Op_b' -> `List [`String "b*"]
  | O.Op_n -> `List [`String "n"]
  | O.Op_W -> `List [`String "W"]
  | O.Op_W' -> `List [`String "W*"]
  | O.Op_BT -> `List [`String "BT"]
  | O.Op_ET -> `List [`String "ET"]
  | O.Op_q -> `List [`String "q"]
  | O.Op_Q -> `List [`String "Q"]
  | O.Op_h -> `List [`String "h"]
  | O.Op_T' -> `List [`String "T*"]
  | O.Op_EMC -> `List [`String "EMC"]
  | O.Op_BX -> `List [`String "BX"]
  | O.Op_EX -> `List [`String "EX"]
  | O.Op_re (a, b, c, d) ->
      `List [mkfloat a; mkfloat b; mkfloat c; mkfloat d; `String "re"]
  | O.Op_k (c, m, y, k) ->
      `List [mkfloat c; mkfloat m; mkfloat y; mkfloat k; `String "k"]
  | O.Op_m (a, b) -> `List [mkfloat a; mkfloat b; `String "m"]
  | O.Op_l (a, b) -> `List [mkfloat a; mkfloat b; `String "l"]
  | O.Op_BDC (s, obj) -> `List [`String s; json_of_object pdf (fun _ -> ()) no_stream_data false obj; `String "BDC"]
  | O.Op_gs s -> `List [`String s; `String "gs"]
  | O.Op_Do s -> `List [`String s; `String "Do"]
  | O.Op_CS s -> `List [`String s; `String "CS"]
  | O.Op_SCN fs -> `List ((map (fun x -> mkfloat x) fs) @ [`String "SCN"])
  | O.Op_j j -> `List [mkint j; `String "j"] 
  | O.Op_cm t ->
      `List
        [mkfloat t.Pdftransform.a; mkfloat t.Pdftransform.b; mkfloat t.Pdftransform.c;
         mkfloat t.Pdftransform.d; mkfloat t.Pdftransform.e; mkfloat t.Pdftransform.f;
         `String "cm"]
  | O.Op_d (fl, y) ->
      `List [`List (map (fun x -> mkfloat x) fl); mkfloat y; `String "d"]
  | O.Op_w w -> `List [mkfloat w; `String "w"]
  | O.Op_J j -> `List [mkint j; `String "J"]
  | O.Op_M m -> `List [mkfloat m; `String "M"]
  | O.Op_ri s -> `List [`String s; `String "ri"]
  | O.Op_i i -> `List [mkint i; `String "i"]
  | O.Op_c (a, b, c, d, e, f) ->
      `List
        [mkfloat a; mkfloat b; mkfloat c;
         mkfloat d; mkfloat e; mkfloat f; `String "c"]
  | O.Op_v (a, b, c, d) ->
      `List
        [mkfloat a; mkfloat b; mkfloat c;
         mkfloat d; `String "v"]
  | O.Op_y (a, b, c, d) ->
      `List
        [mkfloat a; mkfloat b; mkfloat c;
         mkfloat d; `String "y"]
  | O.Op_Tc c -> `List [mkfloat c; `String "Tc"]
  | O.Op_Tw w -> `List [mkfloat w; `String "Tw"]
  | O.Op_Tz z -> `List [mkfloat z; `String "Tz"]
  | O.Op_TL l -> `List [mkfloat l; `String "TL"]
  | O.Op_Tf (k, s) -> `List [`String k; mkfloat s; `String "Tf"]
  | O.Op_Tr i -> `List [mkint i; `String "Tr"]
  | O.Op_Ts k -> `List [mkfloat k; `String "Ts"]
  | O.Op_Td (k, k') -> `List [mkfloat k; mkfloat k'; `String "Td"]
  | O.Op_TD (k, k') -> `List [mkfloat k; mkfloat k'; `String "TD"]
  | O.Op_Tm t ->
      `List
        [mkfloat t.Pdftransform.a; mkfloat t.Pdftransform.b; mkfloat t.Pdftransform.c;
         mkfloat t.Pdftransform.d; mkfloat t.Pdftransform.e; mkfloat t.Pdftransform.f;
         `String "Tm"]
  | O.Op_Tj s -> `List [`String s; `String "Tj"]
  | O.Op_TJ pdfobject -> `List [json_of_object pdf (fun _ -> ()) no_stream_data false pdfobject; `String "TJ"]
  | O.Op_' s -> `List [`String s; `String "'"]
  | O.Op_'' (k, k', s) -> `List [mkfloat k; mkfloat k'; `String s; `String "''"]
  | O.Op_d0 (k, k') -> `List [mkfloat k; mkfloat k'; `String "d0"]
  | O.Op_d1 (a, b, c, d, e, f) ->
      `List
        [mkfloat a; mkfloat b; mkfloat c;
         mkfloat d; mkfloat e; mkfloat f; `String "d1"]
  | O.Op_cs s -> `List [`String s; `String "cs"]
  | O.Op_SC fs -> `List (map (fun x -> mkfloat x) fs @ [`String "SC"])
  | O.Op_sc fs -> `List (map (fun x -> mkfloat x) fs @ [`String "sc"])
  | O.Op_scn fs -> `List (map (fun x -> mkfloat x) fs @ [`String "scn"])
  | O.Op_G k -> `List [mkfloat k; `String "G"]
  | O.Op_g k -> `List [mkfloat k; `String "g"]
  | O.Op_RG (r, g, b) -> `List [mkfloat r; mkfloat g; mkfloat b; `String "RG"]
  | O.Op_rg (r, g, b) -> `List [mkfloat r; mkfloat g; mkfloat b; `String "rg"]
  | O.Op_K (c, m, y, k) -> `List [mkfloat c; mkfloat m; mkfloat y; mkfloat k; `String "K"]
  | O.Op_sh s -> `List [`String s; `String "sh"]
  | O.Op_MP s -> `List [`String s; `String "MP"]
  | O.Op_BMC s -> `List [`String s; `String "BMC"]
  | O.Op_Unknown s -> `List [`String s; `String "Unknown"]
  | O.Op_SCNName (s, fs) ->
      `List (map (fun x -> mkfloat x) fs @ [`String s; `String "SCNName"])
  | O.Op_scnName (s, fs) ->
      `List (map (fun x -> mkfloat x) fs @ [`String s; `String "scnName"])
  | O.InlineImage (dict, data) ->
      `List [json_of_object pdf (fun _ -> ()) no_stream_data false dict; `String (Pdfio.string_of_bytes data); `String "InlineImage"]
  | O.Op_DP (s, obj) ->
      `List [`String s; json_of_object pdf (fun _ -> ()) no_stream_data false obj; `String "DP"]

(* parse_stream needs pdf and resources. These are for lexing of inline images,
 * looking up the colourspace. *)
let parse_content_stream pdf resources bs =
  let ops = O.parse_stream pdf resources [bs] in
    `List (map (json_of_op pdf false) ops)

(* Make sure each page only has one page content stream. Otherwise,
   if not split on op boundaries, each one would fail to parse on its own. *)
let precombine_page_content pdf =
  let pages' =
    map
      (fun page ->
         match page.Pdfpage.content with
           [] | [_] -> page
         | _ ->
           let operators =
             Pdfops.parse_operators pdf page.Pdfpage.resources page.Pdfpage.content
           in
             {page with Pdfpage.content = [Pdfops.stream_of_ops operators]}
      )
      (Pdfpage.pages_of_pagetree pdf)
  in
    Pdfpage.change_pages true pdf pages'

(* PDF strings (except /ID in the trailer dictionary) are either PDFDocEncoding
or UTF16BE. Many times the UTF16BE can all be represented in PDFDocEncoding.
In this case, there are just lots of \000 bytes getting in the way making the
JSON hard to edit. So we preprocess such simple UTF16BE strings into
PDFDocEncoding. *)
let preprocess_string s =
  if Pdftext.is_unicode s
    then Pdftext.pdfdocstring_of_utf8 (Pdftext.utf8_of_pdfdocstring s)
    else s

let rec ppstring_single_object pdf = function
  | Pdf.Dictionary d -> Pdf.recurse_dict (ppstring_single_object pdf) d
  | (Pdf.Stream {contents = (Pdf.Dictionary dict, data)}) ->
      Pdf.Stream {contents = (Pdf.recurse_dict (ppstring_single_object pdf) dict, data)}
  | Pdf.Array a -> Pdf.recurse_array (ppstring_single_object pdf) a
  | Pdf.String s -> Pdf.String (preprocess_string s)
  | x -> x

let preprocess_strings pdf =
    Pdf.objselfmap (ppstring_single_object pdf) pdf;
    pdf.Pdf.trailerdict <- ppstring_single_object pdf pdf.Pdf.trailerdict

let json_of_pdf
  ~parse_content ~no_stream_data ~decompress_streams
  pdf
=
  preprocess_strings pdf;
  let pdf = if parse_content then precombine_page_content pdf else pdf in
  if decompress_streams then
    Pdf.objiter (fun _ obj -> Pdfcodec.decode_pdfstream_until_unknown pdf obj) pdf;
  Pdf.remove_unreferenced pdf;
  let trailerdict = (0, json_of_object pdf (fun x -> ()) no_stream_data false pdf.P.trailerdict) in
  let parameters =
    (-1, json_of_object pdf (fun x -> ()) false false
      (Pdf.Dictionary [("/CPDFJSONformatversion", Pdf.Integer 2);
                       ("/CPDFJSONcontentparsed", Pdf.Boolean parse_content);
                       ("/CPDFJSONstreamdataincluded", Pdf.Boolean (not no_stream_data));
                       ("/CPDFJSONmajorpdfversion", Pdf.Integer pdf.Pdf.major);
                       ("/CPDFJSONminorpdfversion", Pdf.Integer pdf.Pdf.minor);
                      ]))
  in
  let content_streams = ref [] in
  let fcs n =
    content_streams := n::!content_streams;
    if parse_content then Pdfcodec.decode_pdfstream_until_unknown pdf (P.lookup_obj pdf n)
  in
  let pairs =
    let ps = ref [] in
      P.objiter
        (fun i pdfobj ->
          ps := (i, json_of_object pdf fcs no_stream_data parse_content pdfobj)::!ps)
        pdf;
      parameters::trailerdict::sort compare !ps
  in
    let pairs_parsed =
      if not parse_content then pairs else
        map
          (fun (objnum, obj) ->
             if mem objnum !content_streams then
               begin match obj with
               | `Assoc ["S", `List [dict; `String _]] ->
                   let streamdata =
                     match P.lookup_obj pdf objnum with
                     | P.Stream {contents = (_, P.Got b)} -> b
                     | _ -> error "JSON: stream not decoded"
                   in
                     let dict =
                       match dict with
                       | `Assoc d ->
                           `Assoc (option_map (function (("/Filter" | "/Length"), _) -> None | (a, b) -> Some (a, b)) d)
                       | _ -> assert false
                     in
                       (objnum,
                        `Assoc ["S", `List [dict; parse_content_stream pdf (P.Dictionary []) streamdata]])
               | _ -> error "json_of_pdf: stream parsing inconsistency"
               end
             else
               (objnum, obj))
          pairs
    in
      `List
        (map
          (fun (objnum, jsonobj) -> `List [`Int objnum; jsonobj])
          pairs_parsed)

let to_output o ~parse_content ~no_stream_data ~decompress_streams pdf =
  let json = json_of_pdf ~parse_content ~no_stream_data ~decompress_streams pdf in
    match o.Pdfio.out_caml_channel with
    | Some ch -> J.pretty_to_channel ch json
    | None -> o.Pdfio.output_string (J.pretty_to_string json)

let of_input i =
  try
    match i.Pdfio.caml_channel with
    | Some ch ->
        pdf_of_json (J.from_channel ch)
    | None -> 
        let content = Pdfio.string_of_bytes (Pdfio.bytes_of_input i 0 i.Pdfio.in_channel_length) in
          pdf_of_json (J.from_string content)
  with
    e -> error (Printexc.to_string e)