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Module « numpy.matlib »

Fonction packbits - module numpy.matlib

Signature de la fonction packbits

Description

help(numpy.matlib.packbits)

packbits(a, /, axis=None, bitorder='big')

Packs the elements of a binary-valued array into bits in a uint8 array.

The result is padded to full bytes by inserting zero bits at the end.

Parameters
----------
a : array_like
    An array of integers or booleans whose elements should be packed to
    bits.
axis : int, optional
    The dimension over which bit-packing is done.
    ``None`` implies packing the flattened array.
bitorder : {'big', 'little'}, optional
    The order of the input bits. 'big' will mimic bin(val),
    ``[0, 0, 0, 0, 0, 0, 1, 1] => 3 = 0b00000011``, 'little' will
    reverse the order so ``[1, 1, 0, 0, 0, 0, 0, 0] => 3``.
    Defaults to 'big'.

Returns
-------
packed : ndarray
    Array of type uint8 whose elements represent bits corresponding to the
    logical (0 or nonzero) value of the input elements. The shape of
    `packed` has the same number of dimensions as the input (unless `axis`
    is None, in which case the output is 1-D).

See Also
--------
unpackbits: Unpacks elements of a uint8 array into a binary-valued output
            array.

Examples
--------
>>> import numpy as np
>>> a = np.array([[[1,0,1],
...                [0,1,0]],
...               [[1,1,0],
...                [0,0,1]]])
>>> b = np.packbits(a, axis=-1)
>>> b
array([[[160],
        [ 64]],
       [[192],
        [ 32]]], dtype=uint8)

Note that in binary 160 = 1010 0000, 64 = 0100 0000, 192 = 1100 0000,
and 32 = 0010 0000.

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