scipy.ndimage.fourier_shift

scipy.ndimage.fourier_shift(input, shift, n=-1, axis=-1, output=None)

Multi-dimensional fourier shift filter.

The array is multiplied with the fourier transform of a shift operation.

Parameters:

input : array_like

The input array.

shift : float or sequence

The size of the box used for filtering. If a float, shift is the same for all axes. If a sequence, shift has to contain one value for each axis.

n : int, optional

If n is negative (default), then the input is assumed to be the result of a complex fft. If n is larger than or equal to zero, the input is assumed to be the result of a real fft, and n gives the length of the array before transformation along the real transform direction.

axis : int, optional

The axis of the real transform.

output : ndarray, optional

If given, the result of shifting the input is placed in this array. None is returned in this case.

Returns:

fourier_shift : ndarray or None

The shifted input. If output is given as a parameter, None is returned.

Examples

>>> from scipy import ndimage, misc
>>> import matplotlib.pyplot as plt
>>> import numpy.fft
>>> fig, (ax1, ax2) = plt.subplots(1, 2)
>>> plt.gray()  # show the filtered result in grayscale
>>> ascent = misc.ascent()
>>> input_ = numpy.fft.fft2(ascent)
>>> result = ndimage.fourier_shift(input_, shift=200)
>>> result = numpy.fft.ifft2(result)
>>> ax1.imshow(ascent)
>>> ax2.imshow(result.real)  # the imaginary part is an artifact
>>> plt.show()