547 lines
22 KiB
OCaml
547 lines
22 KiB
OCaml
(* Truetype font parsing and subsetting *)
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open Pdfutil
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open Pdfio
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(* ./cpdf -font-ttf ~/repos/pdfs/fonts/NimbusRoman-Regular.ttf -add-text foo hello.pdf -o out.pdf *)
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type t =
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{flags : int;
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minx : int;
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miny : int;
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maxx : int;
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maxy : int;
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italicangle : int;
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ascent : int;
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descent : int;
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capheight : int;
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stemv : int;
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xheight : int;
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avgwidth : int;
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maxwidth : int;
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firstchar : int;
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lastchar : int;
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widths : int array;
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subset : Pdfio.bytes;
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tounicode : Pdfio.bytes option}
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let dbg = ref true (* text-based debug *)
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let tounicode_preamble =
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"/CIDInit /ProcSet findresource begin\n\
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12 dict begin\n\
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begincmap\n\
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/CIDSystemInfo <<\n\
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/Registry (Adobe)\n\
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/Ordering (UCS)\n\
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/Supplement 0\n\
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>> def\n\
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/CMapName /Adobe-Identity-UCS def\n\
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/CMapType 2 def\n\
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1 begincodespacerange\n\
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<00><FF>\n\
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endcodespacerange\n"
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let tounicode_postamble =
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"endbfrange\n\
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endcmap\n\
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CMapName currentdict /CMap defineresource pop\n\
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end\n\
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end\n"
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let tounicode_map s us =
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let b = Buffer.create 1024 in
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let s = ref s in
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Buffer.add_string b tounicode_preamble;
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Buffer.add_string b (Printf.sprintf "%i beginbfrange\n" (length us));
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iter
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(fun u -> Buffer.add_string b (Printf.sprintf "<%02x><%02x><%04x>" !s !s u);
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s := !s + 1)
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us;
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Buffer.add_string b tounicode_postamble;
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bytes_of_string (Buffer.contents b)
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let required_tables =
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["head"; "hhea"; "loca"; "cmap"; "maxp"; "cvt "; "glyf"; "prep"; "hmtx"; "fpgm"]
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(* 32-bit signed fixed-point number (16.16) returned as two ints *)
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let read_fixed b =
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let a = getval_31 b 16 in
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let b = getval_31 b 16 in
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a, b
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(* 16-bit unsigned integer *)
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let read_ushort b = getval_31 b 16
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(* 32-bit unsigned integer *)
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let read_ulong b = getval_32 b 32
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(* Signed byte *)
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let read_byte b = getval_31 b 8
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(* Signed short *)
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let read_short b = sign_extend 16 (getval_31 b 16)
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(* f2dot14 - 2 bit signed integer part, 14 bit unsigned fraction *)
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let read_f2dot14 b =
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let v = read_ushort b in
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float_of_int (sign_extend 2 (v lsr 14)) +. (float_of_int (v land 0x3FFF) /. 16384.)
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(* discard n bytes *)
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let discard_bytes b n =
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for x = 1 to n do ignore (getval_31 b 8) done
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let pdf_unit unitsPerEm x =
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int_of_float (float_of_int x *. 1000. /. float_of_int unitsPerEm +. 0.5)
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let string_of_tag t =
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Printf.sprintf "%c%c%c%c"
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(char_of_int (i32toi (Int32.shift_right t 24)))
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(char_of_int (i32toi (Int32.logand 0x000000FFl (Int32.shift_right t 16))))
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(char_of_int (i32toi (Int32.logand 0x000000FFl (Int32.shift_right t 8))))
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(char_of_int (i32toi (Int32.logand 0x000000FFl t)))
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let read_format_6_encoding_table b =
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let firstCode = read_ushort b in
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let entryCount = read_ushort b in
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let t = null_hash () in
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try
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for x = firstCode to firstCode + entryCount - 1 do
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Hashtbl.add t x (read_ushort b)
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done;
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t
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with
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e -> failwith ("bad format 6 table: " ^ Printexc.to_string e ^ "\n")
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(* fixme might need indexToLocFormat here, to undo the "clever" formula. *)
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let read_format_4_encoding_table b =
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let t = null_hash () in
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let segCountX2 = read_ushort b in
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let segCount = segCountX2 / 2 in
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let searchRange = read_ushort b in
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let entrySelector = read_ushort b in
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let rangeShift = read_ushort b in
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let endCodes = Array.init segCount (fun _ -> read_ushort b) in
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let _ (* reservedPad *) = read_ushort b in
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let startCodes = Array.init segCount (fun _ -> read_ushort b) in
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let idDelta = Array.init segCount (fun _ -> read_ushort b) in
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let idRangeOffset = Array.init segCount (fun _ -> read_ushort b) in
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if !dbg then
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begin
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Printf.printf "segCount = %i, searchRange = %i, entrySelector = %i, rangeShift = %i\n" segCount searchRange entrySelector rangeShift;
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Printf.printf "endCodes\n";
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print_ints (Array.to_list endCodes);
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Printf.printf "startCodes\n";
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print_ints (Array.to_list startCodes);
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Printf.printf "idDelta\n";
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print_ints (Array.to_list idDelta);
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Printf.printf "idRangeOffset\n";
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print_ints (Array.to_list idRangeOffset);
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end;
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for seg = 0 to segCount - 1 do
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let ec = endCodes.(seg) in
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let sc = startCodes.(seg) in
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let del = idDelta.(seg) in
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let ro = idRangeOffset.(seg) in
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for c = sc to ec do
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if ro = 0 then
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Hashtbl.add t c ((c + del) mod 65536)
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else
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let sum = (c - sc) + del in
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()
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done
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done;
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t
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let read_encoding_table fmt length version b =
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match fmt with
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| 0 ->
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let t = null_hash () in
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for x = 0 to 255 do Hashtbl.add t x (read_byte b) done;
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t
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| 4 -> read_format_4_encoding_table b
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| 6 -> read_format_6_encoding_table b
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| n -> raise (Pdf.PDFError "read_encoding_table: format %i not known\n%!")
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let read_loca_table indexToLocFormat numGlyphs b =
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match indexToLocFormat with
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| 0 -> Array.init (numGlyphs + 1) (function _ -> i32ofi (read_ushort b * 2))
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| 1 -> Array.init (numGlyphs + 1) (function _ -> read_ulong b)
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| _ -> raise (Pdf.PDFError "Unknown indexToLocFormat in read_loca_table")
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let write_loca_table subset cmap indexToLocFormat bs loca =
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let locnums = null_hash () in
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Hashtbl.add locnums 0 (); (* .notdef *)
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iter
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(fun u ->
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let locnum = Hashtbl.find cmap u in
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if !dbg then Printf.printf "write_loca_table: Unicode %i is at location number %i\n" u locnum;
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Hashtbl.add locnums locnum ())
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subset;
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let write_entry loc position =
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match indexToLocFormat with
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| 0 -> putval bs 16 (i32div position 2l)
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| 1 -> putval bs 32 position
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| _ -> raise (Pdf.PDFError "Unknown indexToLocFormat in write_loca_table")
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in
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let pos = ref 0l in
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let pairs =
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map
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(fun loc ->
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let len = i32sub loca.(loc + 1) loca.(loc) in
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let r = (loc, !pos) in
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pos := i32add !pos len;
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r)
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(sort compare (map fst (list_of_hashtbl locnums)))
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in
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let pairs = Array.of_list (pairs @ [(Array.length loca - 1, !pos)]) in
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Array.iteri
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(fun i (loc, off) ->
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if i <> Array.length pairs - 1 then
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begin
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write_entry loc off;
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let loc', off' = pairs.(i + 1) in
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for x = 0 to loc' - loc - 2 do write_entry (loc + x) off' done
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end
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else
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write_entry loc off)
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pairs
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(* Write the notdef glyf, and any others in the subset *)
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let write_glyf_table subset cmap bs mk_b glyfoffset loca =
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if !dbg then Printf.printf "***write_glyf_table\n";
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let locnums = null_hash () in
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Hashtbl.add locnums 0 (); (* .notdef *)
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iter
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(fun u ->
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let locnum = Hashtbl.find cmap u in
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if !dbg then Printf.printf "write_glyf_table: Unicode %i is at location number %i\n" u locnum;
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Hashtbl.add locnums locnum ())
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subset;
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let locnums = sort compare (map fst (list_of_hashtbl locnums)) in
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if !dbg then (Printf.printf "We want glyfs for locations: "; iter (Printf.printf "%i ") locnums; Printf.printf "\n");
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let byteranges = map (fun x -> (loca.(x), loca.(x + 1))) locnums in
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if !dbg then (Printf.printf "Byte ranges: "; iter (fun (a, b) -> Printf.printf "(%li, %li) " a b) byteranges; Printf.printf "\n");
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let len = List.fold_left i32add 0l (map (fun (a, b) -> i32sub b a) byteranges) in
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Printf.printf "THE LENGTH is %li\n" len;
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let write_bytes bs a l =
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if !dbg then Printf.printf "glyf: write_bytes %li %li\n" a l;
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let b = mk_b (i32toi (i32add glyfoffset a)) in
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for x = 1 to i32toi l do putval bs 8 (getval_32 b 8) done
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in
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iter (fun (a, b) -> write_bytes bs a (i32sub b a)) byteranges;
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let padding = 4 - i32toi len mod 4 in
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Printf.printf "padding = %i bytes\n" padding;
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for x = 1 to padding do putval bs 8 0l done
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let read_os2_table unitsPerEm b blength =
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let version = read_ushort b in
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if !dbg then Printf.printf "OS/2 table blength = %i bytes, version number = %i\n" blength version;
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let xAvgCharWidth = pdf_unit unitsPerEm (read_short b) in
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discard_bytes b 64; (* discard 14 entries usWeightClass...fsLastCharIndex *)
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(* -- end of original OS/2 Version 0 Truetype table. Must check length before reading now. *)
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let sTypoAscender = if blength > 68 then pdf_unit unitsPerEm (read_short b) else 0 in
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let sTypoDescender = if blength > 68 then pdf_unit unitsPerEm (read_short b) else 0 in
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discard_bytes b 6; (* discard sTypoLineGap...usWinDescent *)
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(* -- end of OpenType version 0 table *)
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discard_bytes b 8; (* discard ulCodePageRange1, ulCodePageRange2 *)
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(* -- end of OpenType version 1 table *)
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let sxHeight = if version < 2 then 0 else pdf_unit unitsPerEm (read_short b) in
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let sCapHeight = if version < 2 then 0 else pdf_unit unitsPerEm (read_short b) in
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(sTypoAscender, sTypoDescender, sCapHeight, sxHeight, xAvgCharWidth)
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let read_post_table b =
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discard_bytes b 4; (* discard version *)
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let italicangle, n = read_fixed b in
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italicangle
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(* Eventually:
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Set bit 6 for non symbolic. (nb bit 1 is actualy bit 0 etc.)
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Set bit 7 if italicangle <> 0
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Set bit 2 if serif ?
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Set bit 1 if fixed pitch (calculate from widths) *)
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let calculate_flags italicangle =
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let italic = if italicangle <> 0 then 1 else 0 in
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32 lor italic lsl 6
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let calculate_limits subset =
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if subset = [] then (0, 255) else
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extremes (sort compare subset)
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let calculate_stemv () = 0
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let read_hhea_table b =
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discard_bytes b 34;
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read_ushort b (* numOfLongHorMetrics *)
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let read_hmtx_table numOfLongHorMetrics b =
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Array.init
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numOfLongHorMetrics
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(fun _ -> let r = read_ushort b in ignore (read_short b); r)
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(* For widths, we need the unicode code, not the unencoded byte *)
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let unicode_codepoint_of_pdfcode encoding_table glyphlist_table p =
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try
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hd (Hashtbl.find glyphlist_table (Hashtbl.find encoding_table p))
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with
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Not_found -> 0
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let calculate_widths unitsPerEm encoding firstchar lastchar subset cmapdata hmtxdata =
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if lastchar < firstchar then failwith "lastchar < firschar" else
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(*if !dbg then List.iter (fun (a, b) -> Printf.printf "%i -> %i\n" a b) (sort compare (list_of_hashtbl cmapdata));*)
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let encoding_table = Pdftext.table_of_encoding encoding in
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let glyphlist_table = Pdfglyphlist.glyph_hashes () in
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Array.init
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(lastchar - firstchar + 1)
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(fun pos ->
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let code = pos + firstchar in
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if !dbg then Printf.printf "code %i --> " code;
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let code = unicode_codepoint_of_pdfcode encoding_table glyphlist_table code in
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if !dbg then Printf.printf "unicode %i --> " code;
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if subset <> [] && not (mem code subset) then 0 else
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try
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let glyphnum = Hashtbl.find cmapdata code in
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if !dbg then Printf.printf "glyph number %i --> " glyphnum;
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let width = hmtxdata.(glyphnum) in
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if !dbg then Printf.printf "width %i\n" width;
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pdf_unit unitsPerEm width
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with e -> if !dbg then Printf.printf "no width for %i\n" code; 0)
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let calculate_maxwidth unitsPerEm hmtxdata =
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pdf_unit unitsPerEm (hd (sort (fun a b -> compare b a) (Array.to_list hmtxdata)))
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let remove_unneeded_tables major minor tables indexToLocFormat subset encoding cmap loca mk_b glyfoffset data =
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let tables = Array.of_list (sort (fun (_, _, o, _) (_, _, o', _) -> compare o o') tables) in
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let tablesout = ref [] in
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let cut = ref 0l in
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if !dbg then Printf.printf "***Input:\n";
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Array.iteri
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(fun i (tag, checkSum, offset, ttlength) ->
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if !dbg then Printf.printf "tag = %li = %s, offset = %li\n" tag (string_of_tag tag) offset;
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if mem (string_of_tag tag) required_tables then
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tablesout := (tag, checkSum, i32sub offset !cut, ttlength)::!tablesout
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else
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cut := i32add !cut (match tables.(i + 1) with (_, _, offset', _) -> i32sub offset' offset))
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tables;
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(* Reduce offsets by the reduction in header table size *)
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let header_size_reduction = i32ofi (16 * (Array.length tables - length !tablesout)) in
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let glyf_table_size_reduction = ref 0l in
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let newtables =
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Array.of_list
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(map
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(fun (tag, checksum, offset, ttlength) ->
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let ttlength =
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if string_of_tag tag = "glyf" && subset <> [] then
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let bs = make_write_bitstream () in
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write_glyf_table subset cmap bs mk_b glyfoffset loca;
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let newlen = i32ofi (bytes_size (bytes_of_write_bitstream bs)) in
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glyf_table_size_reduction := i32sub ttlength newlen;
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newlen
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else ttlength
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in
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let offset' =
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i32sub
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(i32sub offset header_size_reduction)
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(if string_of_tag tag = "glyf" then 0l else !glyf_table_size_reduction)
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in
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(tag, checksum, offset', ttlength))
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(rev !tablesout))
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in
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Printf.printf "glyf_table_size_reduction = %li\n" !glyf_table_size_reduction;
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if !dbg then Printf.printf "***Reduced:\n";
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Array.iter
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(fun (tag, checkSum, offset, ttlength) ->
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if !dbg then Printf.printf "tag = %li = %s, offset = %li\n" tag (string_of_tag tag) offset)
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newtables;
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let bs = make_write_bitstream () in
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(* table directory *)
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let numtables = Array.length newtables in
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putval bs 16 (i32ofi major);
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putval bs 16 (i32ofi minor);
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putval bs 16 (i32ofi numtables); (* numTables *)
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putval bs 16 (i32ofi (16 * pow2lt numtables)); (* searchRange *)
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putval bs 16 (i32ofi (int_of_float (log (float_of_int (pow2lt numtables))))); (* entrySelector *)
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putval bs 16 (i32ofi (numtables * 16)); (* rangeShift *)
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Array.iter
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(fun (tag, checkSum, offset, ttlength) ->
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putval bs 32 tag;
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putval bs 32 checkSum;
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putval bs 32 offset;
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putval bs 32 ttlength)
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newtables;
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(* find each table in original data, calculating the length from the next offset.
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On the last, copy until we run out of data *)
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let findtag tag =
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let off = ref 0l in
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let len = ref None in
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begin try
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for x = 0 to Array.length tables - 1 do
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let t, _, offset, _ = tables.(x) in
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if t = tag then
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begin
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off := offset;
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if x < Array.length tables - 1 then
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len := Some (let _, _, nextoffset, _ = tables.(x + 1) in i32sub nextoffset offset);
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raise Exit
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end
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done;
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failwith "failed to find table"
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with
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Exit -> (!off, !len)
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end
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in
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Array.iter
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(fun (tag, _, _, _) ->
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if !dbg then Printf.printf "Writing %s table\n" (string_of_tag tag);
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if string_of_tag tag = "loca" && subset <> [] then
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write_loca_table subset cmap indexToLocFormat bs loca
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else if string_of_tag tag = "glyf" && subset <> [] then
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write_glyf_table subset cmap bs mk_b glyfoffset loca
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else
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match findtag tag with
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| (og_off, Some len) ->
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let b = mk_b (i32toi og_off) in
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for x = 0 to i32toi len - 1 do putval bs 8 (getval_32 b 8) done
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| (og_off, None) ->
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let b = mk_b (i32toi og_off) in
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try
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while true do putval bs 8 (getval_32 b 8) done
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with
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_ -> ())
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newtables;
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let bytes = bytes_of_write_bitstream bs in
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if !dbg then Printf.printf "Made subset font of length %i bytes\n" (bytes_size bytes);
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let o = open_out_bin "fontout.ttf" in
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output_string o (string_of_bytes bytes);
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close_out o;
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bytes
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let parse ?(subset=[]) data encoding =
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let mk_b byte_offset = bitbytes_of_input (let i = input_of_bytes data in i.seek_in byte_offset; i) in
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let b = mk_b 0 in
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let major, minor = read_fixed b in
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if !dbg then Printf.printf "Truetype font version %i.%i\n" major minor;
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let numTables = read_ushort b in
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let searchRange = read_ushort b in
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let entrySelector = read_ushort b in
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let rangeShift = read_ushort b in
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if !dbg then Printf.printf "numTables = %i, searchRange = %i, entrySelector = %i, rangeShift = %i\n"
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numTables searchRange entrySelector rangeShift;
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let tables = ref [] in
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for x = 1 to numTables do
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let tag = read_ulong b in
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let checkSum = read_ulong b in
|
|
let offset = read_ulong b in
|
|
let ttlength = read_ulong b in
|
|
if !dbg then Printf.printf "tag = %li = %s, checkSum = %li, offset = %li, ttlength = %li\n"
|
|
tag (string_of_tag tag) checkSum offset ttlength;
|
|
tables =| (tag, checkSum, offset, ttlength);
|
|
done;
|
|
let headoffset, headlength =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "head") !tables with
|
|
| (_, _, o, l)::_ -> o, l
|
|
| [] -> raise (Pdf.PDFError "No maxp table found in TrueType font")
|
|
in
|
|
let b = mk_b (i32toi headoffset) in
|
|
discard_bytes b 18;
|
|
let unitsPerEm = read_ushort b in
|
|
discard_bytes b 16;
|
|
let minx = pdf_unit unitsPerEm (read_short b) in
|
|
let miny = pdf_unit unitsPerEm (read_short b) in
|
|
let maxx = pdf_unit unitsPerEm (read_short b) in
|
|
let maxy = pdf_unit unitsPerEm (read_short b) in
|
|
discard_bytes b 6;
|
|
let indexToLocFormat = read_short b in
|
|
let _ (*glyphDataFormat*) = read_short b in
|
|
if !dbg then Printf.printf "head table: indexToLocFormat is %i\n" indexToLocFormat;
|
|
if !dbg then Printf.printf "box %i %i %i %i\n" minx miny maxx maxy;
|
|
let os2 =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "OS/2") !tables with
|
|
| (_, _, o, l)::_ -> Some (o, l)
|
|
| [] -> None
|
|
in
|
|
let ascent, descent, capheight, xheight, avgwidth =
|
|
match os2 with
|
|
| None -> raise (Pdf.PDFError "No os/2 table found in truetype font")
|
|
| Some (o, l) -> let b = mk_b (i32toi o) in read_os2_table unitsPerEm b (i32toi l)
|
|
in
|
|
let italicangle =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "post") !tables with
|
|
| (_, _, o, _)::_ -> read_post_table (mk_b (i32toi o))
|
|
| _ -> 0
|
|
in
|
|
if !dbg then
|
|
Printf.printf "ascent %i descent %i capheight %i xheight %i avgwidth %i\n"
|
|
ascent descent capheight xheight avgwidth;
|
|
let cmap =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "cmap") !tables with
|
|
| (_, _, o, l)::_ -> Some (o, l)
|
|
| [] -> None
|
|
in
|
|
let glyphcodes = ref (null_hash ()) in
|
|
begin match cmap with
|
|
| None ->
|
|
let t = null_hash () in
|
|
for x = 0 to 255 do Hashtbl.add t x x done;
|
|
glyphcodes := t
|
|
| Some (cmapoffset, cmaplength) ->
|
|
let b = mk_b (i32toi cmapoffset) in
|
|
let cmap_version = read_ushort b in
|
|
let num_encoding_tables = read_ushort b in
|
|
if !dbg then Printf.printf "cmap version %i. There are %i encoding tables\n"
|
|
cmap_version num_encoding_tables;
|
|
for x = 1 to num_encoding_tables do
|
|
let platform_id = read_ushort b in
|
|
let encoding_id = read_ushort b in
|
|
let subtable_offset = read_ulong b in
|
|
if !dbg then Printf.printf "subtable %i. platform_id = %i, encoding_id = %i, subtable_offset = %li\n"
|
|
x platform_id encoding_id subtable_offset;
|
|
let b = mk_b (i32toi cmapoffset + i32toi subtable_offset) in
|
|
let fmt = read_ushort b in
|
|
let lngth = read_ushort b in
|
|
let version = read_ushort b in
|
|
if !dbg then Printf.printf "subtable has format %i, length %i, version %i\n" fmt lngth version;
|
|
let got_glyphcodes = read_encoding_table fmt length version b in
|
|
glyphcodes := got_glyphcodes
|
|
done;
|
|
end;
|
|
let maxpoffset, maxplength =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "maxp") !tables with
|
|
| (_, _, o, l)::_ -> o, l
|
|
| [] -> raise (Pdf.PDFError "No maxp table found in TrueType font")
|
|
in
|
|
let b = mk_b (i32toi maxpoffset) in
|
|
let mmajor, mminor = read_fixed b in
|
|
let numGlyphs = read_ushort b in
|
|
if !dbg then Printf.printf "maxp table version %i.%i: This font has %i glyphs\n" mmajor mminor numGlyphs;
|
|
let locaoffset, localength =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "loca") !tables with
|
|
| (_, _, o, l)::_ -> o, l
|
|
| [] -> raise (Pdf.PDFError "No loca table found in TrueType font")
|
|
in
|
|
let flags = calculate_flags italicangle in
|
|
let firstchar, lastchar = calculate_limits subset in
|
|
let numOfLongHorMetrics =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "hhea") !tables with
|
|
| (_, _, o, l)::_ -> let b = mk_b (i32toi o) in read_hhea_table b
|
|
| _ -> 0
|
|
in
|
|
let hmtxdata =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "hmtx") !tables with
|
|
| (_, _, o, _)::_ -> read_hmtx_table numOfLongHorMetrics (mk_b (i32toi o))
|
|
| [] -> raise (Pdf.PDFError "No hmtx table found in TrueType font")
|
|
in
|
|
let widths = calculate_widths unitsPerEm encoding firstchar lastchar subset !glyphcodes hmtxdata in
|
|
let maxwidth = calculate_maxwidth unitsPerEm hmtxdata in
|
|
let stemv = calculate_stemv () in
|
|
let b = mk_b (i32toi locaoffset) in
|
|
let loca = read_loca_table indexToLocFormat numGlyphs b in
|
|
let glyfoffset, glyflength =
|
|
match keep (function (t, _, _, _) -> string_of_tag t = "glyf") !tables with
|
|
| (_, _, o, l)::_ -> o, l
|
|
| [] -> raise (Pdf.PDFError "No glyf table found in TrueType font")
|
|
in
|
|
let subset = remove_unneeded_tables major minor !tables indexToLocFormat subset encoding !glyphcodes loca mk_b glyfoffset data in
|
|
[{flags; minx; miny; maxx; maxy; italicangle; ascent; descent;
|
|
capheight; stemv; xheight; avgwidth; maxwidth; firstchar; lastchar;
|
|
widths; subset; tounicode = None}]
|