Source code for fontTools.misc.fixedTools

"""fontTools.misc.fixedTools.py -- tools for working with fixed numbers.
"""

from __future__ import print_function, division, absolute_import
from fontTools.misc.py23 import *
import logging

log = logging.getLogger(__name__)

__all__ = [
	"fixedToFloat",
	"floatToFixed",
	"ensureVersionIsLong",
	"versionToFixed",
]

[docs]def fixedToFloat(value, precisionBits): """Converts a fixed-point number to a float, choosing the float that has the shortest decimal reprentation. Eg. to convert a fixed number in a 2.14 format, use precisionBits=14. This is pretty slow compared to a simple division. Use sporadically. precisionBits is only supported up to 16. """ if not value: return 0.0 scale = 1 << precisionBits value /= scale eps = .5 / scale lo = value - eps hi = value + eps # If the range of valid choices spans an integer, return the integer. if int(lo) != int(hi): return float(round(value)) fmt = "%.8f" lo = fmt % lo hi = fmt % hi assert len(lo) == len(hi) and lo != hi for i in range(len(lo)): if lo[i] != hi[i]: break period = lo.find('.') assert period < i fmt = "%%.%df" % (i - period) value = fmt % value return float(value)
[docs]def floatToFixed(value, precisionBits): """Converts a float to a fixed-point number given the number of precisionBits. Ie. int(round(value * (1<<precisionBits))). """ return int(round(value * (1<<precisionBits)))
[docs]def ensureVersionIsLong(value): """Ensure a table version is an unsigned long (unsigned short major, unsigned short minor) instead of a float.""" if value < 0x10000: newValue = floatToFixed(value, 16) log.warning( "Table version value is a float: %.4f; " "fix to use hex instead: 0x%08x", value, newValue) value = newValue return value
[docs]def versionToFixed(value): """Converts a table version to a fixed""" value = int(value, 0) if value.startswith("0") else float(value) value = ensureVersionIsLong(value) return value