333 lines
13 KiB
OCaml
333 lines
13 KiB
OCaml
(* Truetype font parsing and subsetting *)
|
|
open Pdfutil
|
|
open Pdfio
|
|
|
|
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 : Pdfio.bytes}
|
|
|
|
let dbg = ref true (* text-based debug *)
|
|
|
|
(* 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)
|
|
|
|
(* fword *)
|
|
let read_fword = read_short
|
|
let read_ufword = read_ushort
|
|
|
|
(* 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 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
|
|
(* FIXME: This format can address glyphs > 255, but we don't support that
|
|
elsewhere yet --- but we read the whole format table nonethless *)
|
|
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 read_encoding_table fmt length version b =
|
|
match fmt with
|
|
| 0 ->
|
|
let t = null_hash () in
|
|
for x = 0 to 255 do Hashtbl.add t x (read_byte b) done;
|
|
t
|
|
| 4 -> read_format_4_encoding_table b
|
|
| 6 -> 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 =
|
|
let fix_empties arr =
|
|
for x = 1 to Array.length arr - 1 do
|
|
if arr.(x) = arr.(x - 1) then arr.(x - 1) <- -1l
|
|
done;
|
|
if arr <> [||] then arr.(Array.length arr - 1) <- -1l
|
|
in
|
|
match indexToLocFormat with
|
|
| 0 ->
|
|
let arr = Array.init (numGlyphs + 1) (function _ -> i32ofi (read_ushort b * 2)) in
|
|
fix_empties arr; arr
|
|
| 1 ->
|
|
let arr = Array.init (numGlyphs + 1) (function _ -> read_ulong b) in
|
|
fix_empties arr; arr
|
|
| _ -> raise (Pdf.PDFError "Unknown indexToLocFormat in read_loca_table")
|
|
|
|
(* FIXME length checking *)
|
|
let read_os2_table 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 = 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 = read_short b in
|
|
let sTypoDescender = read_short b 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 read_short b in
|
|
let sCapHeight = if version < 2 then 0 else 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 () = 80
|
|
|
|
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)
|
|
|
|
let calculate_widths firstchar lastchar subset (cmapdata : (int, int) Hashtbl.t) (hmtxdata : int array) =
|
|
if lastchar < firstchar then failwith "lastchar < firschar" else
|
|
if !dbg then List.iter (fun (a, b) -> Printf.printf "%i -> %i\n" a b) (sort compare (list_of_hashtbl cmapdata));
|
|
Array.init
|
|
(lastchar - firstchar + 1)
|
|
(fun pos ->
|
|
let code = pos + firstchar in
|
|
if !dbg then Printf.printf "code %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;
|
|
width
|
|
with e -> if !dbg then Printf.printf "no width for %i\n" code; 0)
|
|
|
|
let calculate_maxwidth hmtxdata =
|
|
hd (sort (fun a b -> compare b a) (Array.to_list hmtxdata))
|
|
|
|
let parse ?(subset=[]) data =
|
|
let subset = map fst subset in
|
|
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 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 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 major, minor = 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" major minor numGlyphs;
|
|
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 36;
|
|
let minx = read_fword b in
|
|
let miny = read_fword b in
|
|
let maxx = read_fword b in
|
|
let maxy = read_fword 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 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 firstchar lastchar subset !glyphcodes hmtxdata in
|
|
let maxwidth = calculate_maxwidth hmtxdata in
|
|
let stemv = calculate_stemv () in
|
|
let b = mk_b (i32toi locaoffset) in
|
|
let offsets = read_loca_table indexToLocFormat numGlyphs b in
|
|
let subset = data in
|
|
{flags; minx; miny; maxx; maxy; italicangle; ascent; descent;
|
|
capheight; stemv; xheight; avgwidth; maxwidth; firstchar; lastchar;
|
|
widths; subset}
|