py2store.utils.affine_conversion

utils to carry out affine transformations (of indices)

class py2store.utils.affine_conversion.AffineConverter(scale=1.0, offset=0.0)

Getting a callable that will perform an affine conversion. Note, it does it as

(val - offset) * scale

(Note slope-intercept style (though there is the .from_slope_and_intercept constructor method for that)

Inverse is available through the inv method, performing:

val / scale + offset

>>> convert = AffineConverter(scale=0.5, offset=1)
>>> convert(0)
-0.5
>>> convert(10)
4.5
>>> convert.inv(4)
9.0
>>> convert.inv(4.5)
10.0

py2store.utils.affine_conversion.get_affine_converter_and_inverse(scale=1, offset=0, source_type_cast=None, target_type_cast=None)

Getting two affine functions with given scale and offset, that are inverse of each other. Namely (for input val):

(val - offset) * scale and val / scale + offset

Note this is not “slope intercept” style!!

The source_type_cast and target_type_case (optional), allow the user to specify if these transformations need to be further cast to a given type. :param scale: :param offset: :param source_type_cast: function to apply to input :param target_type_cast: function to apply to output :return: Two single val functions: affine_converter, inverse_affine_converter

Note: Code is a lot more complex than the basic operations it performs. The reason was a worry of efficiency since the functions that are returned are intended to be used in long loops.

See also: ocore.utils.conversion.AffineConverter

>>> affine_converter, inverse_affine_converter = get_affine_converter_and_inverse(scale=0.5,offset=1)
>>> affine_converter(0)
-0.5
>>> affine_converter(10)
4.5
>>> inverse_affine_converter(4)
9.0
>>> inverse_affine_converter(4.5)
10.0
>>> affine_converter, inverse_affine_converter = get_affine_converter_and_inverse(scale=0.5,offset=1,target_type_cast=int)
>>> affine_converter(10)
4