Avoid squeezing shared content streams
This commit is contained in:
John Whitington
parent
ef5f6b13e4
commit
2f8beb0e0d
142
cpdf.ml
142
cpdf.ml
|
|
@ -109,9 +109,13 @@ let really_squeeze pdf =
|
|||
pdf.Pdf.objects <- !pdfr.Pdf.objects;
|
||||
pdf.Pdf.trailerdict <- !pdfr.Pdf.trailerdict
|
||||
|
||||
(* Squeeze the form xobject at objnum. FIXME: For old PDFs (< v1.2) any
|
||||
resources from the page (or its ancestors in the page tree!) are also needed -
|
||||
we must merge them with the ones from the xobject itself. *)
|
||||
(* Squeeze the form xobject at objnum.
|
||||
|
||||
FIXME: For old PDFs (< v1.2) any resources from the page (or its ancestors in
|
||||
the page tree!) are also needed - we must merge them with the ones from the
|
||||
xobject itself. However, it it safe for now -- in the unlikely event that the
|
||||
resources actually need to be available, the parse will fail, the squeeze of
|
||||
this object will fail, and we bail out. *)
|
||||
let xobjects_done = ref []
|
||||
|
||||
let squeeze_form_xobject pdf objnum =
|
||||
|
|
@ -142,60 +146,92 @@ let squeeze_form_xobject pdf objnum =
|
|||
end
|
||||
| _ -> ()
|
||||
|
||||
(* For a list of indirects representing content streams, make sure that none of
|
||||
them are duplicated in the PDF. This indicates sharing, which parsing and
|
||||
rewriting the streams might destroy, thus making the file bigger. FIXME: The
|
||||
correct thing to do is to preserve the multiple content streams. *)
|
||||
let no_duplicates content_stream_numbers stream_numbers =
|
||||
not
|
||||
(mem false
|
||||
(map
|
||||
(fun n -> length (keep (eq n) content_stream_numbers) < 2)
|
||||
stream_numbers))
|
||||
|
||||
(* Give a list of content stream numbers, given a page reference number *)
|
||||
let content_streams_of_page pdf refnum =
|
||||
match Pdf.direct pdf (Pdf.lookup_obj pdf refnum) with
|
||||
Pdf.Dictionary dict ->
|
||||
begin match lookup "/Contents" dict with
|
||||
Some (Pdf.Indirect i) -> [i]
|
||||
| Some (Pdf.Array x) ->
|
||||
option_map (function Pdf.Indirect i -> Some i | _ -> None) x
|
||||
| _ -> []
|
||||
end
|
||||
| _ -> []
|
||||
|
||||
(* For each object in the PDF marked with /Type /Page, for each /Contents
|
||||
indirect reference or array of such, decode and recode that content stream. *)
|
||||
let squeeze_all_content_streams pdf =
|
||||
xobjects_done := [];
|
||||
Pdf.objiter
|
||||
(fun objnum _ ->
|
||||
match Pdf.lookup_obj pdf objnum with
|
||||
Pdf.Dictionary dict as d
|
||||
when
|
||||
Pdf.lookup_direct pdf "/Type" d = Some (Pdf.Name "/Page")
|
||||
->
|
||||
let resources =
|
||||
match Pdf.lookup_direct pdf "/Resources" d with
|
||||
Some d -> d
|
||||
| None -> Pdf.Dictionary []
|
||||
in
|
||||
begin try
|
||||
let newstream =
|
||||
let content_streams =
|
||||
match lookup "/Contents" dict with
|
||||
Some (Pdf.Indirect i) ->
|
||||
begin match Pdf.direct pdf (Pdf.Indirect i) with
|
||||
Pdf.Array x -> x
|
||||
| _ -> [Pdf.Indirect i]
|
||||
end
|
||||
| Some (Pdf.Array x) -> x
|
||||
| _ -> raise Not_found
|
||||
in
|
||||
Pdfops.stream_of_ops
|
||||
(Pdfops.parse_operators pdf resources content_streams)
|
||||
let page_reference_numbers = Pdf.page_reference_numbers pdf in
|
||||
let all_content_streams_in_doc =
|
||||
flatten (map (content_streams_of_page pdf) page_reference_numbers)
|
||||
in
|
||||
xobjects_done := [];
|
||||
Pdf.objiter
|
||||
(fun objnum _ ->
|
||||
match Pdf.lookup_obj pdf objnum with
|
||||
Pdf.Dictionary dict as d
|
||||
when
|
||||
Pdf.lookup_direct pdf "/Type" d = Some (Pdf.Name "/Page")
|
||||
->
|
||||
let resources =
|
||||
match Pdf.lookup_direct pdf "/Resources" d with
|
||||
Some d -> d
|
||||
| None -> Pdf.Dictionary []
|
||||
in
|
||||
let newdict =
|
||||
Pdf.add_dict_entry
|
||||
d "/Contents" (Pdf.Indirect (Pdf.addobj pdf newstream))
|
||||
in
|
||||
Pdf.addobj_given_num pdf (objnum, newdict);
|
||||
(* Now process all xobjects related to this page *)
|
||||
begin match Pdf.lookup_direct pdf "/XObject" resources with
|
||||
Some (Pdf.Dictionary xobjs) ->
|
||||
iter
|
||||
(function
|
||||
(_, Pdf.Indirect i) -> squeeze_form_xobject pdf i
|
||||
| _ -> failwith "squeeze_xobject")
|
||||
xobjs
|
||||
| _ -> ()
|
||||
end
|
||||
with
|
||||
(* No /Contents, which is ok. Or a parsing failure due to
|
||||
uninherited resources. FIXME: Add support for inherited
|
||||
resources. *)
|
||||
Not_found -> ()
|
||||
end
|
||||
| _ -> ())
|
||||
pdf
|
||||
begin try
|
||||
let content_streams =
|
||||
match lookup "/Contents" dict with
|
||||
Some (Pdf.Indirect i) ->
|
||||
begin match Pdf.direct pdf (Pdf.Indirect i) with
|
||||
Pdf.Array x -> x
|
||||
| _ -> [Pdf.Indirect i]
|
||||
end
|
||||
| Some (Pdf.Array x) -> x
|
||||
| _ -> raise Not_found
|
||||
in
|
||||
if
|
||||
no_duplicates
|
||||
all_content_streams_in_doc
|
||||
(map (function Pdf.Indirect i -> i | _ -> assert false) content_streams)
|
||||
then
|
||||
let newstream =
|
||||
Pdfops.stream_of_ops
|
||||
(Pdfops.parse_operators pdf resources content_streams)
|
||||
in
|
||||
let newdict =
|
||||
Pdf.add_dict_entry
|
||||
d "/Contents" (Pdf.Indirect (Pdf.addobj pdf newstream))
|
||||
in
|
||||
Pdf.addobj_given_num pdf (objnum, newdict);
|
||||
(* Now process all xobjects related to this page *)
|
||||
begin match Pdf.lookup_direct pdf "/XObject" resources with
|
||||
Some (Pdf.Dictionary xobjs) ->
|
||||
iter
|
||||
(function
|
||||
(_, Pdf.Indirect i) -> squeeze_form_xobject pdf i
|
||||
| _ -> failwith "squeeze_xobject")
|
||||
xobjs
|
||||
| _ -> ()
|
||||
end
|
||||
with
|
||||
(* No /Contents, which is ok. Or a parsing failure due to
|
||||
uninherited resources. FIXME: Add support for inherited
|
||||
resources. *)
|
||||
Not_found -> ()
|
||||
end
|
||||
| _ -> ())
|
||||
pdf
|
||||
|
||||
(* We run squeeze enough times to reach a fixed point in the cardinality of the
|
||||
* object map *)
|
||||
|
|
|
|||
Loading…
Reference in New Issue