| """ |
| Various round-to-integer helpers. |
| """ |
| |
| import math |
| import functools |
| import logging |
| |
| log = logging.getLogger(__name__) |
| |
| __all__ = [ |
| "noRound", |
| "otRound", |
| "maybeRound", |
| "roundFunc", |
| ] |
| |
| def noRound(value): |
| return value |
| |
| def otRound(value): |
| """Round float value to nearest integer towards ``+Infinity``. |
| |
| The OpenType spec (in the section on `"normalization" of OpenType Font Variations <https://docs.microsoft.com/en-us/typography/opentype/spec/otvaroverview#coordinate-scales-and-normalization>`_) |
| defines the required method for converting floating point values to |
| fixed-point. In particular it specifies the following rounding strategy: |
| |
| for fractional values of 0.5 and higher, take the next higher integer; |
| for other fractional values, truncate. |
| |
| This function rounds the floating-point value according to this strategy |
| in preparation for conversion to fixed-point. |
| |
| Args: |
| value (float): The input floating-point value. |
| |
| Returns |
| float: The rounded value. |
| """ |
| # See this thread for how we ended up with this implementation: |
| # https://github.com/fonttools/fonttools/issues/1248#issuecomment-383198166 |
| return int(math.floor(value + 0.5)) |
| |
| def maybeRound(v, tolerance, round=otRound): |
| rounded = round(v) |
| return rounded if abs(rounded - v) <= tolerance else v |
| |
| def roundFunc(tolerance, round=otRound): |
| if tolerance < 0: |
| raise ValueError("Rounding tolerance must be positive") |
| |
| if tolerance == 0: |
| return noRound |
| |
| if tolerance >= .5: |
| return round |
| |
| return functools.partial(maybeRound, tolerance=tolerance, round=round) |