diff options
Diffstat (limited to 'Lib/fontTools/misc/fixedTools.py')
| -rw-r--r-- | Lib/fontTools/misc/fixedTools.py | 320 |
1 files changed, 161 insertions, 159 deletions
diff --git a/Lib/fontTools/misc/fixedTools.py b/Lib/fontTools/misc/fixedTools.py index 6ec7d06e..33004287 100644 --- a/Lib/fontTools/misc/fixedTools.py +++ b/Lib/fontTools/misc/fixedTools.py @@ -23,16 +23,16 @@ import logging log = logging.getLogger(__name__) __all__ = [ - "MAX_F2DOT14", - "fixedToFloat", - "floatToFixed", - "floatToFixedToFloat", - "floatToFixedToStr", - "fixedToStr", - "strToFixed", - "strToFixedToFloat", - "ensureVersionIsLong", - "versionToFixed", + "MAX_F2DOT14", + "fixedToFloat", + "floatToFixed", + "floatToFixedToFloat", + "floatToFixedToStr", + "fixedToStr", + "strToFixed", + "strToFixedToFloat", + "ensureVersionIsLong", + "versionToFixed", ] @@ -40,212 +40,214 @@ MAX_F2DOT14 = 0x7FFF / (1 << 14) def fixedToFloat(value, precisionBits): - """Converts a fixed-point number to a float given the number of - precision bits. + """Converts a fixed-point number to a float given the number of + precision bits. - Args: - value (int): Number in fixed-point format. - precisionBits (int): Number of precision bits. + Args: + value (int): Number in fixed-point format. + precisionBits (int): Number of precision bits. - Returns: - Floating point value. + Returns: + Floating point value. - Examples:: + Examples:: - >>> import math - >>> f = fixedToFloat(-10139, precisionBits=14) - >>> math.isclose(f, -0.61883544921875) - True - """ - return value / (1 << precisionBits) + >>> import math + >>> f = fixedToFloat(-10139, precisionBits=14) + >>> math.isclose(f, -0.61883544921875) + True + """ + return value / (1 << precisionBits) def floatToFixed(value, precisionBits): - """Converts a float to a fixed-point number given the number of - precision bits. + """Converts a float to a fixed-point number given the number of + precision bits. - Args: - value (float): Floating point value. - precisionBits (int): Number of precision bits. + Args: + value (float): Floating point value. + precisionBits (int): Number of precision bits. - Returns: - int: Fixed-point representation. + Returns: + int: Fixed-point representation. - Examples:: + Examples:: - >>> floatToFixed(-0.61883544921875, precisionBits=14) - -10139 - >>> floatToFixed(-0.61884, precisionBits=14) - -10139 - """ - return otRound(value * (1 << precisionBits)) + >>> floatToFixed(-0.61883544921875, precisionBits=14) + -10139 + >>> floatToFixed(-0.61884, precisionBits=14) + -10139 + """ + return otRound(value * (1 << precisionBits)) def floatToFixedToFloat(value, precisionBits): - """Converts a float to a fixed-point number and back again. + """Converts a float to a fixed-point number and back again. - By converting the float to fixed, rounding it, and converting it back - to float again, this returns a floating point values which is exactly - representable in fixed-point format. + By converting the float to fixed, rounding it, and converting it back + to float again, this returns a floating point values which is exactly + representable in fixed-point format. - Note: this **is** equivalent to ``fixedToFloat(floatToFixed(value))``. + Note: this **is** equivalent to ``fixedToFloat(floatToFixed(value))``. - Args: - value (float): The input floating point value. - precisionBits (int): Number of precision bits. + Args: + value (float): The input floating point value. + precisionBits (int): Number of precision bits. - Returns: - float: The transformed and rounded value. + Returns: + float: The transformed and rounded value. - Examples:: - >>> import math - >>> f1 = -0.61884 - >>> f2 = floatToFixedToFloat(-0.61884, precisionBits=14) - >>> f1 != f2 - True - >>> math.isclose(f2, -0.61883544921875) - True - """ - scale = 1 << precisionBits - return otRound(value * scale) / scale + Examples:: + >>> import math + >>> f1 = -0.61884 + >>> f2 = floatToFixedToFloat(-0.61884, precisionBits=14) + >>> f1 != f2 + True + >>> math.isclose(f2, -0.61883544921875) + True + """ + scale = 1 << precisionBits + return otRound(value * scale) / scale def fixedToStr(value, precisionBits): - """Converts a fixed-point number to a string representing a decimal float. + """Converts a fixed-point number to a string representing a decimal float. - This chooses the float that has the shortest decimal representation (the least - number of fractional decimal digits). + This chooses the float that has the shortest decimal representation (the least + number of fractional decimal digits). - For example, to convert a fixed-point number in a 2.14 format, use - ``precisionBits=14``:: + For example, to convert a fixed-point number in a 2.14 format, use + ``precisionBits=14``:: - >>> fixedToStr(-10139, precisionBits=14) - '-0.61884' + >>> fixedToStr(-10139, precisionBits=14) + '-0.61884' - This is pretty slow compared to the simple division used in ``fixedToFloat``. - Use sporadically when you need to serialize or print the fixed-point number in - a human-readable form. - It uses nearestMultipleShortestRepr under the hood. + This is pretty slow compared to the simple division used in ``fixedToFloat``. + Use sporadically when you need to serialize or print the fixed-point number in + a human-readable form. + It uses nearestMultipleShortestRepr under the hood. - Args: - value (int): The fixed-point value to convert. - precisionBits (int): Number of precision bits, *up to a maximum of 16*. + Args: + value (int): The fixed-point value to convert. + precisionBits (int): Number of precision bits, *up to a maximum of 16*. - Returns: - str: A string representation of the value. - """ - scale = 1 << precisionBits - return nearestMultipleShortestRepr(value/scale, factor=1.0/scale) + Returns: + str: A string representation of the value. + """ + scale = 1 << precisionBits + return nearestMultipleShortestRepr(value / scale, factor=1.0 / scale) def strToFixed(string, precisionBits): - """Converts a string representing a decimal float to a fixed-point number. + """Converts a string representing a decimal float to a fixed-point number. - Args: - string (str): A string representing a decimal float. - precisionBits (int): Number of precision bits, *up to a maximum of 16*. + Args: + string (str): A string representing a decimal float. + precisionBits (int): Number of precision bits, *up to a maximum of 16*. - Returns: - int: Fixed-point representation. + Returns: + int: Fixed-point representation. - Examples:: + Examples:: - >>> ## to convert a float string to a 2.14 fixed-point number: - >>> strToFixed('-0.61884', precisionBits=14) - -10139 - """ - value = float(string) - return otRound(value * (1 << precisionBits)) + >>> ## to convert a float string to a 2.14 fixed-point number: + >>> strToFixed('-0.61884', precisionBits=14) + -10139 + """ + value = float(string) + return otRound(value * (1 << precisionBits)) def strToFixedToFloat(string, precisionBits): - """Convert a string to a decimal float with fixed-point rounding. + """Convert a string to a decimal float with fixed-point rounding. - This first converts string to a float, then turns it into a fixed-point - number with ``precisionBits`` fractional binary digits, then back to a - float again. + This first converts string to a float, then turns it into a fixed-point + number with ``precisionBits`` fractional binary digits, then back to a + float again. - This is simply a shorthand for fixedToFloat(floatToFixed(float(s))). + This is simply a shorthand for fixedToFloat(floatToFixed(float(s))). - Args: - string (str): A string representing a decimal float. - precisionBits (int): Number of precision bits. + Args: + string (str): A string representing a decimal float. + precisionBits (int): Number of precision bits. - Returns: - float: The transformed and rounded value. + Returns: + float: The transformed and rounded value. - Examples:: + Examples:: - >>> import math - >>> s = '-0.61884' - >>> bits = 14 - >>> f = strToFixedToFloat(s, precisionBits=bits) - >>> math.isclose(f, -0.61883544921875) - True - >>> f == fixedToFloat(floatToFixed(float(s), precisionBits=bits), precisionBits=bits) - True - """ - value = float(string) - scale = 1 << precisionBits - return otRound(value * scale) / scale + >>> import math + >>> s = '-0.61884' + >>> bits = 14 + >>> f = strToFixedToFloat(s, precisionBits=bits) + >>> math.isclose(f, -0.61883544921875) + True + >>> f == fixedToFloat(floatToFixed(float(s), precisionBits=bits), precisionBits=bits) + True + """ + value = float(string) + scale = 1 << precisionBits + return otRound(value * scale) / scale def floatToFixedToStr(value, precisionBits): - """Convert float to string with fixed-point rounding. + """Convert float to string with fixed-point rounding. - This uses the shortest decimal representation (ie. the least - number of fractional decimal digits) to represent the equivalent - fixed-point number with ``precisionBits`` fractional binary digits. - It uses nearestMultipleShortestRepr under the hood. + This uses the shortest decimal representation (ie. the least + number of fractional decimal digits) to represent the equivalent + fixed-point number with ``precisionBits`` fractional binary digits. + It uses nearestMultipleShortestRepr under the hood. - >>> floatToFixedToStr(-0.61883544921875, precisionBits=14) - '-0.61884' + >>> floatToFixedToStr(-0.61883544921875, precisionBits=14) + '-0.61884' - Args: - value (float): The float value to convert. - precisionBits (int): Number of precision bits, *up to a maximum of 16*. + Args: + value (float): The float value to convert. + precisionBits (int): Number of precision bits, *up to a maximum of 16*. - Returns: - str: A string representation of the value. + Returns: + str: A string representation of the value. - """ - scale = 1 << precisionBits - return nearestMultipleShortestRepr(value, factor=1.0/scale) + """ + scale = 1 << precisionBits + return nearestMultipleShortestRepr(value, factor=1.0 / scale) def ensureVersionIsLong(value): - """Ensure a table version is an unsigned long. - - OpenType table version numbers are expressed as a single unsigned long - comprising of an unsigned short major version and unsigned short minor - version. This function detects if the value to be used as a version number - looks too small (i.e. is less than ``0x10000``), and converts it to - fixed-point using :func:`floatToFixed` if so. - - Args: - value (Number): a candidate table version number. - - Returns: - int: A table version number, possibly corrected to fixed-point. - """ - 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 + """Ensure a table version is an unsigned long. + + OpenType table version numbers are expressed as a single unsigned long + comprising of an unsigned short major version and unsigned short minor + version. This function detects if the value to be used as a version number + looks too small (i.e. is less than ``0x10000``), and converts it to + fixed-point using :func:`floatToFixed` if so. + + Args: + value (Number): a candidate table version number. + + Returns: + int: A table version number, possibly corrected to fixed-point. + """ + 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 def versionToFixed(value): - """Ensure a table version number is fixed-point. + """Ensure a table version number is fixed-point. - Args: - value (str): a candidate table version number. + Args: + value (str): a candidate table version number. - Returns: - int: A table version number, possibly corrected to fixed-point. - """ - value = int(value, 0) if value.startswith("0") else float(value) - value = ensureVersionIsLong(value) - return value + Returns: + int: A table version number, possibly corrected to fixed-point. + """ + value = int(value, 0) if value.startswith("0") else float(value) + value = ensureVersionIsLong(value) + return value |