cpdf-source/cpdftruetype.ml

554 lines
23 KiB
OCaml

(* Truetype font parsing and subsetting *)
open Pdfutil
open Pdfio
let fontpack_experiment = true
type t =
{flags : int;
minx : int;
miny : int;
maxx : int;
maxy : int;
italicangle : int;
ascent : int;
descent : int;
capheight : int;
stemv : int;
xheight : int;
avgwidth : int;
maxwidth : int;
firstchar : int;
lastchar : int;
widths : int array;
subset_fontfile : Pdfio.bytes;
subset : int list;
tounicode : (int, string) Hashtbl.t option}
let dbg = ref false
let required_tables =
["head"; "hhea"; "loca"; "cmap"; "maxp"; "cvt "; "glyf"; "prep"; "hmtx"; "fpgm"]
(* 32-bit signed fixed-point number (16.16) returned as two ints *)
let read_fixed b =
let a = getval_31 b 16 in
let b = getval_31 b 16 in
a, b
(* 16-bit unsigned integer *)
let read_ushort b = getval_31 b 16
(* 32-bit unsigned integer *)
let read_ulong b = getval_32 b 32
(* Signed byte *)
let read_byte b = getval_31 b 8
(* Signed short *)
let read_short b = sign_extend 16 (getval_31 b 16)
(* f2dot14 - 2 bit signed integer part, 14 bit unsigned fraction *)
let read_f2dot14 b =
let v = read_ushort b in
float_of_int (sign_extend 2 (v lsr 14)) +. (float_of_int (v land 0x3FFF) /. 16384.)
(* discard n bytes *)
let discard_bytes b n =
for x = 1 to n do ignore (getval_31 b 8) done
let pdf_unit unitsPerEm x =
int_of_float (float_of_int x *. 1000. /. float_of_int unitsPerEm +. 0.5)
let string_of_tag t =
Printf.sprintf "%c%c%c%c"
(char_of_int (i32toi (Int32.shift_right t 24)))
(char_of_int (i32toi (Int32.logand 0x000000FFl (Int32.shift_right t 16))))
(char_of_int (i32toi (Int32.logand 0x000000FFl (Int32.shift_right t 8))))
(char_of_int (i32toi (Int32.logand 0x000000FFl t)))
let read_format_6_encoding_table b =
let firstCode = read_ushort b in
let entryCount = read_ushort b in
let t = null_hash () in
try
for x = firstCode to firstCode + entryCount - 1 do
Hashtbl.add t x (read_ushort b)
done;
t
with
e -> failwith ("bad format 6 table: " ^ Printexc.to_string e ^ "\n")
(* fixme might need indexToLocFormat here, to undo the "clever" formula. *)
let read_format_4_encoding_table b =
let t = null_hash () in
let segCountX2 = read_ushort b in
let segCount = segCountX2 / 2 in
let searchRange = read_ushort b in
let entrySelector = read_ushort b in
let rangeShift = read_ushort b in
let endCodes = Array.init segCount (fun _ -> read_ushort b) in
let _ (* reservedPad *) = read_ushort b in
let startCodes = Array.init segCount (fun _ -> read_ushort b) in
let idDelta = Array.init segCount (fun _ -> read_ushort b) in
let idRangeOffset = Array.init segCount (fun _ -> read_ushort b) in
if !dbg then
begin
Printf.printf "segCount = %i, searchRange = %i, entrySelector = %i, rangeShift = %i\n" segCount searchRange entrySelector rangeShift;
Printf.printf "endCodes\n";
print_ints (Array.to_list endCodes);
Printf.printf "startCodes\n";
print_ints (Array.to_list startCodes);
Printf.printf "idDelta\n";
print_ints (Array.to_list idDelta);
Printf.printf "idRangeOffset\n";
print_ints (Array.to_list idRangeOffset);
end;
for seg = 0 to segCount - 1 do
let ec = endCodes.(seg) in
let sc = startCodes.(seg) in
let del = idDelta.(seg) in
let ro = idRangeOffset.(seg) in
for c = sc to ec do
if ro = 0 then
Hashtbl.add t c ((c + del) mod 65536)
else
let sum = (c - sc) + del in
()
done
done;
t
let print_encoding_table (table : (int, int) Hashtbl.t) =
let l = list_of_hashtbl table in
Printf.printf "There are %i characters in this font\n" (length l);
iter
(fun (c, gi) -> Printf.printf "Char %04X is at glyph index %i\n" c gi)
l
let read_encoding_table fmt length version b =
match fmt with
| 0 ->
(*Printf.printf "read_encoding_table: format 0\n";*)
let t = null_hash () in
for x = 0 to 255 do Hashtbl.add t x (read_byte b) done;
t
| 4 ->
(*Printf.printf "read_encoding_table: format 4\n";*)
read_format_4_encoding_table b
| 6 ->
(*Printf.printf "read_encoding_table: format 6\n";*)
read_format_6_encoding_table b
| n -> raise (Pdf.PDFError "read_encoding_table: format %i not known\n%!")
let read_loca_table indexToLocFormat numGlyphs b =
match indexToLocFormat with
| 0 -> Array.init (numGlyphs + 1) (function _ -> i32ofi (read_ushort b * 2))
| 1 -> Array.init (numGlyphs + 1) (function _ -> read_ulong b)
| _ -> raise (Pdf.PDFError "Unknown indexToLocFormat in read_loca_table")
let write_loca_table subset cmap indexToLocFormat bs loca =
let locnums = null_hash () in
Hashtbl.add locnums 0 (); (* .notdef *)
iter
(fun u ->
let locnum = Hashtbl.find cmap u in
if !dbg then Printf.printf "write_loca_table: Unicode %i is at location number %i\n" u locnum;
Hashtbl.add locnums locnum ())
subset;
let write_entry loc position =
match indexToLocFormat with
| 0 -> putval bs 16 (i32div position 2l)
| 1 -> putval bs 32 position
| _ -> raise (Pdf.PDFError "Unknown indexToLocFormat in write_loca_table")
in
let pos = ref 0l in
let pairs =
map
(fun loc ->
let len = i32sub loca.(loc + 1) loca.(loc) in
let r = (loc, !pos) in
pos := i32add !pos len;
r)
(sort compare (map fst (list_of_hashtbl locnums)))
in
let pairs = Array.of_list (pairs @ [(Array.length loca - 1, !pos)]) in
Array.iteri
(fun i (loc, off) ->
if i <> Array.length pairs - 1 then
begin
write_entry loc off;
let loc', off' = pairs.(i + 1) in
for x = 0 to loc' - loc - 2 do write_entry (loc + x) off' done
end
else
write_entry loc off)
pairs
(* Write the notdef glyf, and any others in the subset *)
let write_glyf_table subset cmap bs mk_b glyfoffset loca =
if !dbg then Printf.printf "***write_glyf_table\n";
let locnums = null_hash () in
Hashtbl.add locnums 0 (); (* .notdef *)
iter
(fun u ->
let locnum = Hashtbl.find cmap u in
if !dbg then Printf.printf "write_glyf_table: Unicode %i is at location number %i\n" u locnum;
Hashtbl.add locnums locnum ())
subset;
let locnums = sort compare (map fst (list_of_hashtbl locnums)) in
if !dbg then (Printf.printf "We want glyfs for locations: "; iter (Printf.printf "%i ") locnums; Printf.printf "\n");
let byteranges = map (fun x -> (loca.(x), loca.(x + 1))) locnums in
if !dbg then (Printf.printf "Byte ranges: "; iter (fun (a, b) -> Printf.printf "(%li, %li) " a b) byteranges; Printf.printf "\n");
let len = List.fold_left i32add 0l (map (fun (a, b) -> i32sub b a) byteranges) in
let write_bytes bs a l =
if !dbg then Printf.printf "glyf: write_bytes %li %li\n" a l;
let b = mk_b (i32toi (i32add glyfoffset a)) in
for x = 1 to i32toi l do putval bs 8 (getval_32 b 8) done
in
iter (fun (a, b) -> write_bytes bs a (i32sub b a)) byteranges;
let padding = 4 - i32toi len mod 4 in
for x = 1 to padding do putval bs 8 0l done;
len
let read_os2_table unitsPerEm b blength =
let version = read_ushort b in
if !dbg then Printf.printf "OS/2 table blength = %i bytes, version number = %i\n" blength version;
let xAvgCharWidth = pdf_unit unitsPerEm (read_short b) in
discard_bytes b 64; (* discard 14 entries usWeightClass...fsLastCharIndex *)
(* -- end of original OS/2 Version 0 Truetype table. Must check length before reading now. *)
let sTypoAscender = if blength > 68 then pdf_unit unitsPerEm (read_short b) else 0 in
let sTypoDescender = if blength > 68 then pdf_unit unitsPerEm (read_short b) else 0 in
discard_bytes b 6; (* discard sTypoLineGap...usWinDescent *)
(* -- end of OpenType version 0 table *)
discard_bytes b 8; (* discard ulCodePageRange1, ulCodePageRange2 *)
(* -- end of OpenType version 1 table *)
let sxHeight = if version < 2 then 0 else pdf_unit unitsPerEm (read_short b) in
let sCapHeight = if version < 2 then 0 else pdf_unit unitsPerEm (read_short b) in
(sTypoAscender, sTypoDescender, sCapHeight, sxHeight, xAvgCharWidth)
let read_post_table b =
discard_bytes b 4; (* discard version *)
let italicangle, n = read_fixed b in
italicangle
(* Eventually:
Set bit 6 for non symbolic. (nb bit 1 is actualy bit 0 etc.)
Set bit 7 if italicangle <> 0
Set bit 2 if serif ?
Set bit 1 if fixed pitch (calculate from widths) *)
let calculate_flags italicangle =
let italic = if italicangle <> 0 then 1 else 0 in
32 lor italic lsl 6
let calculate_limits subset =
if subset = [] then (0, 255) else
extremes (sort compare subset)
let calculate_stemv () = 0
let read_hhea_table b =
discard_bytes b 34;
read_ushort b (* numOfLongHorMetrics *)
let read_hmtx_table numOfLongHorMetrics b =
Array.init
numOfLongHorMetrics
(fun _ -> let r = read_ushort b in ignore (read_short b); r)
(* For widths, we need the unicode code, not the unencoded byte *)
let unicode_codepoint_of_pdfcode encoding_table glyphlist_table p =
try
hd (Hashtbl.find glyphlist_table (Hashtbl.find encoding_table p))
with
Not_found -> 0
let calculate_widths unitsPerEm encoding firstchar lastchar subset cmapdata hmtxdata =
if lastchar < firstchar then failwith "lastchar < firstchar" else
(*if !dbg then List.iter (fun (a, b) -> Printf.printf "%i -> %i\n" a b) (sort compare (list_of_hashtbl cmapdata));*)
let encoding_table = Pdftext.table_of_encoding encoding in
let glyphlist_table = Pdfglyphlist.glyph_hashes () in
Array.init
(lastchar - firstchar + 1)
(fun pos ->
let code = pos + firstchar in
(*if !dbg then Printf.printf "code %i --> " code;*)
let code = unicode_codepoint_of_pdfcode encoding_table glyphlist_table code in
(*if !dbg then Printf.printf "unicode %i --> " code;*)
if subset <> [] && not (mem code subset) then 0 else
try
let glyphnum = Hashtbl.find cmapdata code in
(*if !dbg then Printf.printf "glyph number %i --> " glyphnum;*)
let width = hmtxdata.(glyphnum) in
(*if !dbg then Printf.printf "width %i\n" width;*)
pdf_unit unitsPerEm width
with e -> if !dbg then Printf.printf "no width for %i\n" code; 0)
let calculate_maxwidth unitsPerEm hmtxdata =
pdf_unit unitsPerEm (hd (sort (fun a b -> compare b a) (Array.to_list hmtxdata)))
let padword n =
let n = i32toi n in
let r = n + (if n mod 4 = 0 then 0 else 4 - n mod 4) in
i32ofi r
let subset_font major minor tables indexToLocFormat subset encoding cmap loca mk_b glyfoffset data =
let tables = Array.of_list (sort (fun (_, _, o, _) (_, _, o', _) -> compare o o') tables) in
let tablesout = ref [] in
let cut = ref 0l in
if !dbg then Printf.printf "***Input:\n";
Array.iteri
(fun i (tag, checkSum, offset, ttlength) ->
if !dbg then Printf.printf "tag = %li = %s, offset = %li\n" tag (string_of_tag tag) offset;
if mem (string_of_tag tag) required_tables then
tablesout := (tag, checkSum, i32sub offset !cut, ttlength)::!tablesout
else
cut := i32add !cut (match tables.(i + 1) with (_, _, offset', _) -> i32sub offset' offset))
tables;
(* Reduce offsets by the reduction in header table size *)
let header_size_reduction = i32ofi (16 * (Array.length tables - length !tablesout)) in
let glyf_table_size_reduction = ref 0l in
let newtables =
Array.of_list
(map
(fun (tag, checksum, offset, ttlength) ->
let ttlength =
if string_of_tag tag = "glyf" && subset <> [] then
let bs = make_write_bitstream () in
let newlen = write_glyf_table subset cmap bs mk_b glyfoffset loca in
let paddedlen = i32ofi (bytes_size (bytes_of_write_bitstream bs)) in
if !dbg then Printf.printf "new glyf table length = %li\n" newlen;
glyf_table_size_reduction := i32sub (padword ttlength) paddedlen;
newlen
else ttlength
in
let offset' =
i32sub
(i32sub offset header_size_reduction)
(if string_of_tag tag = "glyf" then 0l else !glyf_table_size_reduction)
in
(tag, checksum, offset', ttlength))
(rev !tablesout))
in
if !dbg then Printf.printf "***Reduced:\n";
Array.iter
(fun (tag, checkSum, offset, ttlength) ->
if !dbg then Printf.printf "tag = %li = %s, offset = %li, length = %li\n" tag (string_of_tag tag) offset ttlength)
newtables;
let bs = make_write_bitstream () in
(* table directory *)
let numtables = Array.length newtables in
putval bs 16 (i32ofi major);
putval bs 16 (i32ofi minor);
putval bs 16 (i32ofi numtables); (* numTables *)
putval bs 16 (i32ofi (16 * pow2lt numtables)); (* searchRange *)
putval bs 16 (i32ofi (int_of_float (log (float_of_int (pow2lt numtables))))); (* entrySelector *)
putval bs 16 (i32ofi (numtables * 16)); (* rangeShift *)
Array.iter
(fun (tag, checkSum, offset, ttlength) ->
putval bs 32 tag;
putval bs 32 checkSum;
putval bs 32 offset;
putval bs 32 ttlength)
newtables;
(* find each table in original data, calculating the length from the next offset.
On the last, copy until we run out of data *)
let findtag tag =
let off = ref 0l in
let len = ref None in
begin try
for x = 0 to Array.length tables - 1 do
let t, _, offset, _ = tables.(x) in
if t = tag then
begin
off := offset;
if x < Array.length tables - 1 then
len := Some (let _, _, nextoffset, _ = tables.(x + 1) in i32sub nextoffset offset);
raise Exit
end
done;
failwith "failed to find table"
with
Exit -> (!off, !len)
end
in
Array.iter
(fun (tag, _, _, _) ->
if !dbg then Printf.printf "Writing %s table\n" (string_of_tag tag);
if string_of_tag tag = "loca" && subset <> [] then
write_loca_table subset cmap indexToLocFormat bs loca
else if string_of_tag tag = "glyf" && subset <> [] then
ignore (write_glyf_table subset cmap bs mk_b glyfoffset loca)
else
match findtag tag with
| (og_off, Some len) ->
let b = mk_b (i32toi og_off) in
for x = 0 to i32toi len - 1 do putval bs 8 (getval_32 b 8) done
| (og_off, None) ->
let b = mk_b (i32toi og_off) in
try
while true do putval bs 8 (getval_32 b 8) done
with
_ -> ())
newtables;
let bytes = bytes_of_write_bitstream bs in
if !dbg then Printf.printf "Made subset font of length %i bytes\n" (bytes_size bytes);
let o = open_out_bin "fontout.ttf" in
output_string o (string_of_bytes bytes);
close_out o;
bytes
let parse ?(subset=[]) data encoding =
let mk_b byte_offset = bitbytes_of_input (let i = input_of_bytes data in i.seek_in byte_offset; i) in
let b = mk_b 0 in
let major, minor = read_fixed b in
if !dbg then Printf.printf "Truetype font version %i.%i\n" major minor;
let numTables = read_ushort b in
let searchRange = read_ushort b in
let entrySelector = read_ushort b in
let rangeShift = read_ushort b in
if !dbg then Printf.printf "numTables = %i, searchRange = %i, entrySelector = %i, rangeShift = %i\n"
numTables searchRange entrySelector rangeShift;
let tables = ref [] in
for x = 1 to numTables do
let tag = read_ulong b in
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 ->
for x = 0 to 255 do Hashtbl.add !glyphcodes x x done
| 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
(*print_encoding_table got_glyphcodes; *)
Hashtbl.iter (Hashtbl.add !glyphcodes) got_glyphcodes;
(*Printf.printf "Retrieved %i cmap entries in total\n" (length (list_of_hashtbl !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 subset_1 = if subset = [] then [] else if fontpack_experiment then tl subset else subset in
let subset_2 = if subset = [] then [] else [hd subset] in
let flags = calculate_flags italicangle in
let firstchar_1, lastchar_1 = calculate_limits subset_1 in
let firstchar_2, lastchar_2 = calculate_limits subset_2 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_1 = calculate_widths unitsPerEm encoding firstchar_1 lastchar_1 subset_1 !glyphcodes hmtxdata in
let widths_2 = calculate_widths unitsPerEm encoding firstchar_2 lastchar_2 subset_2 !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 main_subset =
subset_font major minor !tables indexToLocFormat subset_1
encoding !glyphcodes loca mk_b glyfoffset data
in
let second_subset =
subset_font major minor !tables indexToLocFormat subset_2
encoding !glyphcodes loca mk_b glyfoffset data
in
let second_tounicode =
if subset = [] then None else
let h = null_hash () in
let s = (implode (tl (tl (explode (Pdftext.utf16be_of_codepoints [hd subset]))))) in
Printf.printf "String for tounicode = %S\n" s;
Hashtbl.add h 0 s;
Some h
in
[{flags; minx; miny; maxx; maxy; italicangle; ascent; descent;
capheight; stemv; xheight; avgwidth; maxwidth; firstchar = firstchar_1; lastchar = lastchar_1;
widths = widths_1; subset_fontfile = main_subset; subset = subset_1; tounicode = None}]
@ if fontpack_experiment then
[{flags; minx; miny; maxx; maxy; italicangle; ascent; descent;
capheight; stemv; xheight; avgwidth; maxwidth; firstchar = firstchar_2; lastchar = lastchar_2;
widths = widths_2; subset_fontfile = second_subset; subset = subset_2;
tounicode = second_tounicode}] else []