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Soft mask transformation procedure

This commit is contained in:
John Whitington 2023-04-11 16:08:51 +01:00
parent 572634cd83
commit c04627eae8
1 changed files with 73 additions and 4 deletions
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77
cpdfpage.ml
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@ -4,10 +4,80 @@ open Cpdferror
(* FIXME: Need to take account of inherited resources (among Xobjects and their children - pages
are regularized upon loading). Would be nice to see a failing example first though.
FIXME: What would happen if a pattern was used in a transforming and non-transforming way - we
would have to depulicate - again, no failing example available.
would have to dedupulicate - again, no failing example available.
FIXME: combine change_annotation_matrices, change_pattern_matrices and change_softmask_matrices
into one *)
(* Transparency group soft masks appear to need altering with the inverse of
the transformation matrix. We find them all, deduplicate, and then process
in place. *)
(* FIXME sub-xobjects! *)
(* For each xobject, look in /Resources -> /ExtGState -> /G, and get object number. *)
let rec change_softmask_matrices_xobject pdf xobject =
Printf.printf "change_softmask_matrices_xobject: %s\n" (Pdfwrite.string_of_pdf xobject);
let objnums = ref [] in
begin match xobject with
| Pdf.Indirect i ->
let dict = Pdf.lookup_obj pdf i in
begin match Pdf.lookup_direct pdf "/Resources" dict with
| Some d ->
begin match Pdf.lookup_direct pdf "/ExtGState" d with
| Some (Pdf.Dictionary extgstates) ->
Printf.printf "Found %i extgstates to examine\n" (length extgstates);
iter
(function extgstate ->
match Pdf.direct pdf extgstate with
| Pdf.Dictionary d ->
begin match lookup "/SMask" d with
| Some (Pdf.Dictionary d) ->
begin match lookup "/G" d with
| Some (Pdf.Indirect i) ->
Printf.printf "Collecting objnum %i\n" i;
objnums := i::!objnums
| _ -> ()
end
| _ -> ()
end
| _ -> ())
(map snd extgstates)
| _ -> ()
end
| _ -> ()
end
| _ -> ()
end;
let subxobjects =
match Pdf.lookup_direct pdf "/Resources" xobject with
| Some d ->
begin match Pdf.lookup_direct pdf "/XObject" d with
| Some (Pdf.Dictionary d) -> map snd d
| _ -> []
end
| _ -> []
in
let descendants =
flatten (map (change_softmask_matrices_xobject pdf) subxobjects)
in
descendants @ !objnums
let change_softmask_matrices_page pdf tr page =
let xobjects =
match Pdf.lookup_direct pdf "/XObject" page.Pdfpage.resources with
| Some (Pdf.Dictionary d) -> d
| _ -> []
in
Printf.printf "** page has %i xobjects to process\n" (length xobjects);
let objnums = setify (flatten (map (change_softmask_matrices_xobject pdf) (map snd xobjects))) in
iter
(fun objnum ->
let dict = Pdf.lookup_obj pdf objnum in
let matrix = Pdf.parse_matrix pdf "/Matrix" dict in
let matrix' = Pdftransform.matrix_compose (Pdftransform.matrix_invert tr) matrix in
let dict = Pdf.add_dict_entry dict "/Matrix" (Pdf.make_matrix matrix') in
Pdf.addobj_given_num pdf (objnum, dict))
objnums
(* When we transform a page by wrapping in an [Op_cm], we must also
change any /Matrix entries in (some) pattern dictionaries, including inside
xobjects. We only change the ones used with scn, to avoid pattern dictionaries
@ -76,15 +146,14 @@ and change_pattern_matrices_xobject pdf tr xobj xobjnum =
| _ -> ()
let change_pattern_matrices_page pdf tr page =
change_softmask_matrices_page pdf tr page;
let used = patterns_used pdf page.Pdfpage.content page.Pdfpage.resources in
Printf.printf "Patterns for translation, due to being used as cs / CS";
Hashtbl.iter (fun x _ -> Printf.printf "%s " x) used;
Printf.printf "\n";
{page with Pdfpage.resources = change_pattern_matrices_resources pdf tr page.Pdfpage.resources used}
(* Transparency group soft masks appear to need altering with the inverse of the transformation matrix. We
find them all, deduplicate, and then process in place. *)
let change_softmask_matrices_page pdf tr page = ()
(* Concatenate inverse matrix to each /Matrix entry in those object numbers. *)
(* Output information for each page *)
let output_page_info pdf range =