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#
# PyDvi - A Python Library to Process DVI Stream
# Copyright (C) 2014 Fabrice Salvaire
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
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#
# Audit
#
# - 09/10/2010 Fabrice
#
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"""This module provides functions to convert units used in the TeX world:
* **mm** stands for milimetre,
* **in** stands for inch which corresponds to 25.4 mm,
* **pt** stands for TeX point, there is 72.27 pt in one inch,
* **sp** stands for scale point, there is 2**16 sp in one pt,
* **dpi** stands for dot per inch.
The DVI format uses the measure 100 nm as base unit. A scaled point is defined as a fraction:
* num = 2.54 * 1e7 = 25400000
* den = 7227 * 2**16 = 473628672
* 1 sp = num/den = 5.4 nm
For a resolution of 1200 dpi, a pixel measures 21 um.
"""
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__all__ = ['dpi2mm',
'in2mm', 'in2pt', 'in2sp',
'mm2in',
'pt2in', 'pt2mm', 'pt2sp',
'sp2in', 'sp2mm', 'sp2pt', 'sp2dpi',
]
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import fractions
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# x_in_y means number of x corresponding to 1 y
# 1 in = 72 bp
big_point_in_inch = 72
# 1 cc = 12 dd
didot_in_cicero = 12
# 1157 dd = 1238 pt
didot_in_point = fractions.Fraction(1157, 1238)
# 1 in = 25.4 mm
mm_in_inch = fractions.Fraction(254, 10)
# 1 in = 72.27 pt
point_in_inch = fractions.Fraction(7227, 100)
# 1 pt = 2**16 sp
scaled_point_in_point = 2**16
inch_in_mm = 1 / mm_in_inch
point_in_mm = point_in_inch * inch_in_mm
inch_in_point = 1 / point_in_inch
mm_in_point = 1 / point_in_mm
pt_in_sp = fractions.Fraction(1, scaled_point_in_point)
inch_in_mm_f = float(inch_in_mm)
inch_in_point_f = float(inch_in_point)
mm_in_inch_f = float(mm_in_inch)
mm_in_point_f = float(mm_in_point)
point_in_inch_f = float(point_in_inch)
pt_in_sp_f = float(pt_in_sp)
sp_in_pt_f = float(scaled_point_in_point)
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[docs]def mm2in(x):
"""Convert mm to in"""
return x * inch_in_mm_f
[docs]def in2mm(x):
"""Convert in to mm"""
return x * mm_in_inch_f
[docs]def dpi2mm(x):
"""Convert dpi to mm"""
return mm_in_inch_f / x
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[docs]def in2pt(x):
"""Convert in to pt"""
return x * point_in_inch_f
[docs]def pt2in(x):
"""Convert in to pt"""
return x * inch_in_point_f
[docs]def pt2mm(x):
"""Convert pt to mm"""
return x * mm_in_point_f
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[docs]def sp2pt(x):
"""Convert sp to pt"""
return x * pt_in_sp_f
[docs]def sp2in(x):
"""Convert sp to in"""
return pt2in(sp2pt(x))
[docs]def sp2mm(x):
"""Convert sp to mm"""
return pt2mm(sp2pt(x))
[docs]def sp2dpi(x):
"""Convert sp to dpi"""
return in2pt(sp2pt(x))
[docs]def pt2sp(x):
"""Convert pt to sp"""
return x * sp_in_pt_f
[docs]def in2sp(x):
"""Convert in to sp"""
return pt2sp(in2pt(x))
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#
# End
#
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