shadowfacts/fonttools
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

[tfmLib] New library for reading TFM files

Browse Source 
New library for reading TeX Font Metrics files. Does not support writing
them back.

Fixes https://github.com/fonttools/fonttools/issues/2352
This commit is contained in:
Khaled Hosny 2021-07-05 02:13:09 +02:00
parent 383e70fc39
commit a7ac2de5cd
6 changed files with 550 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

460
Lib/fontTools/tfmLib.py Normal file
View File

@ -0,0 +1,460 @@
"""Module for reading TFM (TeX Font Metrics) files.
The TFM format is described in the TFtoPL WEB source code, whose typeset form
can be found on `CTAN <http://mirrors.ctan.org/info/knuth-pdf/texware/tftopl.pdf>`_.
>>> from fontTools.tfmLib import TFM
>>> tfm = TFM("Tests/tfmLib/data/cmr10.tfm")
>>>
>>> # Accessing an attribute gets you metadata.
>>> tfm.checksum
1274110073
>>> tfm.designsize
10.0
>>> tfm.codingscheme
'TeX text'
>>> tfm.family
'CMR'
>>> tfm.seven_bit_safe_flag
False
>>> tfm.face
234
>>> tfm.extraheader
{}
>>> tfm.fontdimens
{'SLANT': 0.0, 'SPACE': 0.33333396911621094, 'STRETCH': 0.16666698455810547, 'SHRINK': 0.11111164093017578, 'XHEIGHT': 0.4305553436279297, 'QUAD': 1.0000028610229492, 'EXTRASPACE': 0.11111164093017578}
>>> # Accessing a character gets you its metrics.
>>> # “width” is always available, other metrics are available only when
>>> # applicable. All values are relative to “designsize”.
>>> tfm.chars[ord("g")]
{'width': 0.5000019073486328, 'height': 0.4305553436279297, 'depth': 0.1944446563720703, 'italic': 0.013888359069824219}
>>> # Kerning and ligature can be accessed as well.
>>> tfm.kerning[ord("c")]
{104: -0.02777862548828125, 107: -0.02777862548828125}
>>> tfm.ligatures[ord("f")]
{105: ('LIG', 12), 102: ('LIG', 11), 108: ('LIG', 13)}
"""
from types import SimpleNamespace
from fontTools.misc.sstruct import calcsize, unpack, unpack2
SIZES_FORMAT = """
>
lf: h # length of the entire file, in words
lh: h # length of the header data, in words
bc: h # smallest character code in the font
ec: h # largest character code in the font
nw: h # number of words in the width table
nh: h # number of words in the height table
nd: h # number of words in the depth table
ni: h # number of words in the italic correction table
nl: h # number of words in the ligature/kern table
nk: h # number of words in the kern table
ne: h # number of words in the extensible character table
np: h # number of font parameter words
"""
SIZES_SIZE = calcsize(SIZES_FORMAT)
FIXED_FORMAT = "12.20F"
HEADER_FORMAT1 = f"""
>
checksum: L
designsize: {FIXED_FORMAT}
"""
HEADER_FORMAT2 = f"""
{HEADER_FORMAT1}
codingscheme: 40p
"""
HEADER_FORMAT3 = f"""
{HEADER_FORMAT2}
family: 20p
"""
HEADER_FORMAT4 = f"""
{HEADER_FORMAT3}
seven_bit_safe_flag: ?
ignored: x
ignored: x
face: B
"""
HEADER_SIZE1 = calcsize(HEADER_FORMAT1)
HEADER_SIZE2 = calcsize(HEADER_FORMAT2)
HEADER_SIZE3 = calcsize(HEADER_FORMAT3)
HEADER_SIZE4 = calcsize(HEADER_FORMAT4)
LIG_KERN_COMMAND = """
>
skip_byte: B
next_char: B
op_byte: B
remainder: B
"""
BASE_PARAMS = [
"SLANT",
"SPACE",
"STRETCH",
"SHRINK",
"XHEIGHT",
"QUAD",
"EXTRASPACE",
]
MATHSY_PARAMS = [
"NUM1",
"NUM2",
"NUM3",
"DENOM1",
"DENOM2",
"SUP1",
"SUP2",
"SUP3",
"SUB1",
"SUB2",
"SUPDROP",
"SUBDROP",
"DELIM1",
"DELIM2",
"AXISHEIGHT",
]
MATHEX_PARAMS = [
"DEFAULTRULETHICKNESS",
"BIGOPSPACING1",
"BIGOPSPACING2",
"BIGOPSPACING3",
"BIGOPSPACING4",
"BIGOPSPACING5",
]
VANILLA = 0
MATHSY = 1
MATHEX = 2
UNREACHABLE = 0
PASSTHROUGH = 1
ACCESSABLE = 2
NO_TAG = 0
LIG_TAG = 1
LIST_TAG = 2
EXT_TAG = 3
STOP_FLAG = 128
KERN_FLAG = 128
class TFMException(Exception):
def __init__(self, message):
super().__init__(message)
class TFM:
def __init__(self, file):
self._read(file)
def __repr__(self):
return (
f"<TFM"
f" for {self.family}"
f" in {self.codingscheme}"
f" at {self.designsize:g}pt>"
)
def _read(self, file):
if hasattr(file, "read"):
data = file.read()
else:
with open(file, "rb") as fp:
data = fp.read()
self._data = data
if len(data) < SIZES_SIZE:
raise TFMException("Too short input file")
sizes = SimpleNamespace()
unpack2(SIZES_FORMAT, data, sizes)
# Do some file structure sanity checks.
# TeX and TFtoPL do additional functional checks and might even correct
# “errors” in the input file, but we instead try to output the file as
# it is as long as it is parsable, even if the data make no sense.
if sizes.lf < 0:
raise TFMException("The file claims to have negative or zero length!")
if len(data) < sizes.lf * 4:
raise TFMException("The file has fewer bytes than it claims!")
for name, length in vars(sizes).items():
if length < 0:
raise TFMException("The subfile size: '{name}' is negative!")
if sizes.lh < 2:
raise TFMException(f"The header length is only {sizes.lh}!")
if sizes.bc > sizes.ec + 1 or sizes.ec > 255:
raise TFMException(
f"The character code range {sizes.bc}..{sizes.ec} is illegal!"
)
if sizes.nw == 0 or sizes.nh == 0 or sizes.nd == 0 or sizes.ni == 0:
raise TFMException("Incomplete subfiles for character dimensions!")
if sizes.ne > 256:
raise TFMException(f"There are {ne} extensible recipes!")
if sizes.lf != (
6
+ sizes.lh
+ (sizes.ec - sizes.bc + 1)
+ sizes.nw
+ sizes.nh
+ sizes.nd
+ sizes.ni
+ sizes.nl
+ sizes.nk
+ sizes.ne
+ sizes.np
):
raise TFMException("Subfile sizes don’t add up to the stated total")
# Subfile offsets, used in the helper function below. These all are
# 32-bit word offsets not 8-bit byte offsets.
char_base = 6 + sizes.lh - sizes.bc
width_base = char_base + sizes.ec + 1
height_base = width_base + sizes.nw
depth_base = height_base + sizes.nh
italic_base = depth_base + sizes.nd
lig_kern_base = italic_base + sizes.ni
kern_base = lig_kern_base + sizes.nl
exten_base = kern_base + sizes.nk
param_base = exten_base + sizes.ne
# Helper functions for accessing individual data. If this looks
# nonidiomatic Python, I blame the effect of reading the literate WEB
# documentation of TFtoPL.
def char_info(c):
return 4 * (char_base + c)
def width_index(c):
return data[char_info(c)]
def noneexistent(c):
return c < sizes.bc or c > sizes.ec or width_index(c) == 0
def height_index(c):
return data[char_info(c) + 1] // 16
def depth_index(c):
return data[char_info(c) + 1] % 16
def italic_index(c):
return data[char_info(c) + 2] // 4
def tag(c):
return data[char_info(c) + 2] % 4
def remainder(c):
return data[char_info(c) + 3]
def width(c):
r = 4 * (width_base + width_index(c))
return read_fixed(r, "v")["v"]
def height(c):
r = 4 * (height_base + height_index(c))
return read_fixed(r, "v")["v"]
def depth(c):
r = 4 * (depth_base + depth_index(c))
return read_fixed(r, "v")["v"]
def italic(c):
r = 4 * (italic_base + italic_index(c))
return read_fixed(r, "v")["v"]
def exten(c):
return 4 * (exten_base + remainder(c))
def lig_step(i):
return 4 * (lig_kern_base + i)
def lig_kern_command(i):
command = SimpleNamespace()
unpack2(LIG_KERN_COMMAND, data[i:], command)
return command
def kern(i):
r = 4 * (kern_base + i)
return read_fixed(r, "v")["v"]
def param(i):
return 4 * (param_base + i)
def read_fixed(index, key, obj=None):
ret = unpack2(f">;{key}:{FIXED_FORMAT}", data[index:], obj)
return ret[0]
# Set all attributes to empty values regardless of the header size.
unpack(HEADER_FORMAT4, [0] * HEADER_SIZE4, self)
offset = 24
length = sizes.lh * 4
self.extraheader = {}
if length >= HEADER_SIZE4:
rest = unpack2(HEADER_FORMAT4, data[offset:], self)[1]
if self.face < 18:
s = self.face % 2
b = self.face // 2
self.face = "MBL"[b % 3] + "RI"[s] + "RCE"[b // 3]
for i in range(sizes.lh - HEADER_SIZE4 // 4):
rest = unpack2(f">;HEADER{i + 18}:l", rest, self.extraheader)[1]
elif length >= HEADER_SIZE3:
unpack2(HEADER_FORMAT3, data[offset:], self)
elif length >= HEADER_SIZE2:
unpack2(HEADER_FORMAT2, data[offset:], self)
elif length >= HEADER_SIZE1:
unpack2(HEADER_FORMAT1, data[offset:], self)
self.fonttype = VANILLA
scheme = self.codingscheme.upper()
if scheme.startswith("TEX MATH SY"):
self.fonttype = MATHSY
elif scheme.startswith("TEX MATH EX"):
self.fonttype = MATHEX
self.fontdimens = {}
for i in range(sizes.np):
name = f"PARAMETER{i+1}"
if i <= 6:
name = BASE_PARAMS[i]
elif self.fonttype == MATHSY and i <= 21:
name = MATHSY_PARAMS[i - 7]
elif self.fonttype == MATHEX and i <= 12:
name = MATHEX_PARAMS[i - 7]
read_fixed(param(i), name, self.fontdimens)
lig_kern_map = {}
self.right_boundary_char = None
self.left_boundary_char = None
if sizes.nl > 0:
cmd = lig_kern_command(lig_step(0))
if cmd.skip_byte == 255:
self.right_boundary_char = cmd.next_char
cmd = lig_kern_command(lig_step((sizes.nl - 1)))
if cmd.skip_byte == 255:
self.left_boundary_char = 256
r = 256 * cmd.op_byte + cmd.remainder
lig_kern_map[self.left_boundary_char] = r
self.chars = {}
for c in range(sizes.bc, sizes.ec + 1):
if width_index(c) > 0:
self.chars[c] = info = {}
info["width"] = width(c)
if height_index(c) > 0:
info["height"] = height(c)
if depth_index(c) > 0:
info["depth"] = depth(c)
if italic_index(c) > 0:
info["italic"] = italic(c)
char_tag = tag(c)
if char_tag == NO_TAG:
pass
elif char_tag == LIG_TAG:
lig_kern_map[c] = remainder(c)
elif char_tag == LIST_TAG:
info["nextlarger"] = remainder(c)
elif char_tag == EXT_TAG:
info["varchar"] = varchar = {}
for i in range(4):
part = data[exten(c) + i]
if i == 3 or part > 0:
name = "rep"
if i == 0:
name = "top"
elif i == 1:
name = "mid"
elif i == 2:
name = "bot"
if noneexistent(part):
varchar[name] = c
else:
varchar[name] = part
self.ligatures = {}
self.kerning = {}
for c, i in sorted(lig_kern_map.items()):
cmd = lig_kern_command(lig_step(i))
if cmd.skip_byte > STOP_FLAG:
i = 256 * cmd.op_byte + cmd.remainder
while i < sizes.nl:
cmd = lig_kern_command(lig_step(i))
if cmd.skip_byte > STOP_FLAG:
pass
else:
if cmd.op_byte >= KERN_FLAG:
r = 256 * (cmd.op_byte - KERN_FLAG) + cmd.remainder
self.kerning.setdefault(c, {})[cmd.next_char] = kern(r)
else:
r = cmd.op_byte
if r == 4 or (r > 7 and r != 11):
# Ligature step with nonstandard code, we output
# the code verbatim.
lig = r
else:
lig = ""
if r % 4 > 1:
lig += "/"
lig += "LIG"
if r % 2 != 0:
lig += "/"
while r > 3:
lig += ">"
r -= 4
self.ligatures.setdefault(c, {})[cmd.next_char] = (
lig,
cmd.remainder,
)
if cmd.skip_byte >= STOP_FLAG:
break
i += cmd.skip_byte + 1
if __name__ == "__main__":
import sys
tfm = TFM(sys.argv[1])
print(
"\n".join(
x
for x in [
f"tfm.checksum={tfm.checksum}",
f"tfm.designsize={tfm.designsize}",
f"tfm.codingscheme={tfm.codingscheme}",
f"tfm.fonttype={tfm.fonttype}",
f"tfm.family={tfm.family}",
f"tfm.seven_bit_safe_flag={tfm.seven_bit_safe_flag}",
f"tfm.face={tfm.face}",
f"tfm.extraheader={tfm.extraheader}",
f"tfm.fontdimens={tfm.fontdimens}",
f"tfm.right_boundary_char={tfm.right_boundary_char}",
f"tfm.left_boundary_char={tfm.left_boundary_char}",
f"tfm.kerning={tfm.kerning}",
f"tfm.ligatures={tfm.ligatures}",
f"tfm.chars={tfm.chars}",
]
)
)
print(tfm)

BIN
Tests/tfmLib/data/cmex10.tfm Normal file
View File

Binary file not shown.

BIN
Tests/tfmLib/data/cmr10.tfm Normal file
View File

Binary file not shown.

BIN
Tests/tfmLib/data/cmsy10.tfm Normal file
View File

Binary file not shown.

BIN
Tests/tfmLib/data/dummy-space.tfm Normal file
View File

Binary file not shown.

90
Tests/tfmLib/tfmLib_test.py Normal file
View File

@ -0,0 +1,90 @@
import glob
import os
import pytest
from fontTools import tfmLib
DATA_DIR = os.path.join(os.path.dirname(__file__), "data")
@pytest.mark.parametrize("path", glob.glob(f"{DATA_DIR}/cm*.tfm"))
def test_read(path):
tfm = tfmLib.TFM(path)
assert tfm.designsize == 10.0
assert tfm.fontdimens
assert len(tfm.fontdimens) >= 7
assert tfm.extraheader == {}
assert tfm.right_boundary_char is None
assert tfm.left_boundary_char is None
assert len(tfm.chars) == 128
def test_read_boundary_char():
path = os.path.join(DATA_DIR, "dummy-space.tfm")
tfm = tfmLib.TFM(path)
assert tfm.right_boundary_char == 1
assert tfm.left_boundary_char == 256
def test_read_fontdimens_vanilla():
path = os.path.join(DATA_DIR, "cmr10.tfm")
tfm = tfmLib.TFM(path)
assert tfm.fontdimens == {
"SLANT": 0.0,
"SPACE": 0.33333396911621094,
"STRETCH": 0.16666698455810547,
"SHRINK": 0.11111164093017578,
"XHEIGHT": 0.4305553436279297,
"QUAD": 1.0000028610229492,
"EXTRASPACE": 0.11111164093017578,
}
def test_read_fontdimens_mathex():
path = os.path.join(DATA_DIR, "cmex10.tfm")
tfm = tfmLib.TFM(path)
assert tfm.fontdimens == {
"SLANT": 0.0,
"SPACE": 0.0,
"STRETCH": 0.0,
"SHRINK": 0.0,
"XHEIGHT": 0.4305553436279297,
"QUAD": 1.0000028610229492,
"EXTRASPACE": 0.0,
"DEFAULTRULETHICKNESS": 0.03999900817871094,
"BIGOPSPACING1": 0.11111164093017578,
"BIGOPSPACING2": 0.16666698455810547,
"BIGOPSPACING3": 0.19999980926513672,
"BIGOPSPACING4": 0.6000003814697266,
"BIGOPSPACING5": 0.10000038146972656,
}
def test_read_fontdimens_mathsy():
path = os.path.join(DATA_DIR, "cmsy10.tfm")
tfm = tfmLib.TFM(path)
assert tfm.fontdimens == {
"SLANT": 0.25,
"SPACE": 0.0,
"STRETCH": 0.0,
"SHRINK": 0.0,
"XHEIGHT": 0.4305553436279297,
"QUAD": 1.0000028610229492,
"EXTRASPACE": 0.0,
"NUM1": 0.6765079498291016,
"NUM2": 0.39373207092285156,
"NUM3": 0.44373130798339844,
"DENOM1": 0.6859512329101562,
"DENOM2": 0.34484100341796875,
"SUP1": 0.41289234161376953,
"SUP2": 0.36289215087890625,
"SUP3": 0.28888893127441406,
"SUB1": 0.14999961853027344,
"SUB2": 0.24721717834472656,
"SUBDROP": 0.05000019073486328,
"SUPDROP": 0.3861083984375,
"DELIM1": 2.3899993896484375,
"DELIM2": 1.010000228881836,
"AXISHEIGHT": 0.25,
}