Current File : //usr/lib/calibre/calibre/utils/fonts/sfnt/metrics.py
#!/usr/bin/env python3
__license__ = 'GPL v3'
__copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
__docformat__ = 'restructuredtext en'
from calibre.utils.fonts.utils import get_all_font_names
from calibre.utils.fonts.sfnt.container import UnsupportedFont
class FontMetrics:
'''
Get various metrics for the specified sfnt. All the metrics are returned in
units of pixels. To calculate a metric you have to specify the font size
(in pixels) and the horizontal stretch factor (between 0.0 and 1.0).
'''
def __init__(self, sfnt):
for table in (b'head', b'hhea', b'hmtx', b'cmap', b'OS/2', b'post',
b'name', b'maxp'):
if table not in sfnt:
raise UnsupportedFont('This font has no %s table'%table)
self.sfnt = sfnt
self.head = self.sfnt[b'head']
hhea = self.sfnt[b'hhea']
hhea.read_data(self.sfnt[b'hmtx'], self.sfnt[b'maxp'].num_glyphs)
self.ascent = hhea.ascender
self.descent = hhea.descender
self.bbox = (self.head.x_min, self.head.y_min, self.head.x_max,
self.head.y_max)
self._advance_widths = hhea.advance_widths
self.cmap = self.sfnt[b'cmap']
self.units_per_em = self.head.units_per_em
self.os2 = self.sfnt[b'OS/2']
self.os2.read_data()
self.post = self.sfnt[b'post']
self.post.read_data()
self.names = get_all_font_names(self.sfnt[b'name'].raw, raw_is_table=True)
self.is_otf = 'CFF ' in self.sfnt.tables
self._sig = hash(self.sfnt[b'name'].raw)
# Metrics for embedding in PDF
pdf_scale = self.pdf_scale = lambda x:int(round(x*1000./self.units_per_em))
self.pdf_ascent, self.pdf_descent = map(pdf_scale,
(self.os2.typo_ascender, self.os2.typo_descender))
self.pdf_bbox = tuple(map(pdf_scale, self.bbox))
self.pdf_capheight = pdf_scale(getattr(self.os2, 'cap_height',
self.os2.typo_ascender))
self.pdf_avg_width = pdf_scale(self.os2.average_char_width)
self.pdf_stemv = 50 + int((self.os2.weight_class / 65.0) ** 2)
def __hash__(self):
return self._sig
@property
def postscript_name(self):
if 'postscript_name' in self.names:
return self.names['postscript_name'].replace(' ', '-')
try:
return self.names['full_name'].replace(' ', '-')
except KeyError:
return self.names['family_name'].replace(' ', '-')
def underline_thickness(self, pixel_size=12.0):
'Thickness for lines (in pixels) at the specified size'
yscale = pixel_size / self.units_per_em
return self.post.underline_thickness * yscale
def underline_position(self, pixel_size=12.0):
yscale = pixel_size / self.units_per_em
return self.post.underline_position * yscale
def overline_position(self, pixel_size=12.0):
yscale = pixel_size / self.units_per_em
return (self.ascent + 2) * yscale
def strikeout_size(self, pixel_size=12.0):
'The width of the strikeout line, in pixels'
yscale = pixel_size / self.units_per_em
return yscale * self.os2.strikeout_size
def strikeout_position(self, pixel_size=12.0):
'The displacement from the baseline to top of the strikeout line, in pixels'
yscale = pixel_size / self.units_per_em
return yscale * self.os2.strikeout_position
def advance_widths(self, string, pixel_size=12.0, stretch=1.0):
'''
Return the advance widths (in pixels) for all glyphs corresponding to
the characters in string at the specified pixel_size and stretch factor.
'''
if not isinstance(string, str):
raise ValueError('Must supply a unicode object')
chars = tuple(map(ord, string))
cmap = self.cmap.get_character_map(chars)
glyph_ids = (cmap[c] for c in chars)
pixel_size_x = stretch * pixel_size
xscale = pixel_size_x / self.units_per_em
return tuple(i*xscale for i in self.glyph_widths(glyph_ids))
def glyph_widths(self, glyph_ids):
last = len(self._advance_widths)
return tuple(self._advance_widths[i if i < last else -1] for i in
glyph_ids)
def width(self, string, pixel_size=12.0, stretch=1.0):
'The width of the string at the specified pixel size and stretch, in pixels'
return sum(self.advance_widths(string, pixel_size, stretch))
if __name__ == '__main__':
import sys
from calibre.utils.fonts.sfnt.container import Sfnt
with open(sys.argv[-1], 'rb') as f:
raw = f.read()
sfnt = Sfnt(raw)
m = FontMetrics(sfnt)
print('Ascent:', m.pdf_ascent)
print('Descent:', m.pdf_descent)
print('PDF BBox:', m.pdf_bbox)
print('CapHeight:', m.pdf_capheight)
print('AvgWidth:', m.pdf_avg_width)
print('ItalicAngle', m.post.italic_angle)
print('StemV', m.pdf_stemv)
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