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Module « scipy.ndimage »

Fonction generic_filter1d - module scipy.ndimage

Signature de la fonction generic_filter1d

def generic_filter1d(input, function, filter_size, axis=-1, output=None, mode='reflect', cval=0.0, origin=0, extra_arguments=(), extra_keywords=None) 

Description

help(scipy.ndimage.generic_filter1d)

Calculate a 1-D filter along the given axis.

`generic_filter1d` iterates over the lines of the array, calling the
given function at each line. The arguments of the line are the
input line, and the output line. The input and output lines are 1-D
double arrays. The input line is extended appropriately according
to the filter size and origin. The output line must be modified
in-place with the result.

Parameters
----------
input : array_like
    The input array.
function : {callable, scipy.LowLevelCallable}
    Function to apply along given axis.
filter_size : scalar
    Length of the filter.
axis : int, optional
    The axis of `input` along which to calculate. Default is -1.
output : array or dtype, optional
    The array in which to place the output, or the dtype of the
    returned array. By default an array of the same dtype as input
    will be created.
mode : {'reflect', 'constant', 'nearest', 'mirror', 'wrap'}, optional
    The `mode` parameter determines how the input array is extended
    beyond its boundaries. Default is 'reflect'. Behavior for each valid
    value is as follows:

    'reflect' (`d c b a | a b c d | d c b a`)
        The input is extended by reflecting about the edge of the last
        pixel. This mode is also sometimes referred to as half-sample
        symmetric.

    'constant' (`k k k k | a b c d | k k k k`)
        The input is extended by filling all values beyond the edge with
        the same constant value, defined by the `cval` parameter.

    'nearest' (`a a a a | a b c d | d d d d`)
        The input is extended by replicating the last pixel.

    'mirror' (`d c b | a b c d | c b a`)
        The input is extended by reflecting about the center of the last
        pixel. This mode is also sometimes referred to as whole-sample
        symmetric.

    'wrap' (`a b c d | a b c d | a b c d`)
        The input is extended by wrapping around to the opposite edge.

    For consistency with the interpolation functions, the following mode
    names can also be used:

    'grid-mirror'
        This is a synonym for 'reflect'.

    'grid-constant'
        This is a synonym for 'constant'.

    'grid-wrap'
        This is a synonym for 'wrap'.
cval : scalar, optional
    Value to fill past edges of input if `mode` is 'constant'. Default
    is 0.0.
origin : int, optional
    Controls the placement of the filter on the input array's pixels.
    A value of 0 (the default) centers the filter over the pixel, with
    positive values shifting the filter to the left, and negative ones
    to the right.
extra_arguments : sequence, optional
    Sequence of extra positional arguments to pass to passed function.
extra_keywords : dict, optional
    dict of extra keyword arguments to pass to passed function.

Returns
-------
generic_filter1d : ndarray
    Filtered array. Has the same shape as `input`.

Notes
-----
This function also accepts low-level callback functions with one of
the following signatures and wrapped in `scipy.LowLevelCallable`:

.. code:: c

   int function(double *input_line, npy_intp input_length,
                double *output_line, npy_intp output_length,
                void *user_data)
   int function(double *input_line, intptr_t input_length,
                double *output_line, intptr_t output_length,
                void *user_data)

The calling function iterates over the lines of the input and output
arrays, calling the callback function at each line. The current line
is extended according to the border conditions set by the calling
function, and the result is copied into the array that is passed
through ``input_line``. The length of the input line (after extension)
is passed through ``input_length``. The callback function should apply
the filter and store the result in the array passed through
``output_line``. The length of the output line is passed through
``output_length``. ``user_data`` is the data pointer provided
to `scipy.LowLevelCallable` as-is.

The callback function must return an integer error status that is zero
if something went wrong and one otherwise. If an error occurs, you should
normally set the python error status with an informative message
before returning, otherwise a default error message is set by the
calling function.

In addition, some other low-level function pointer specifications
are accepted, but these are for backward compatibility only and should
not be used in new code.

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