scipy.fft.ifft2#
- scipy.fft.ifft2(x, s=None, axes=(-2, -1), norm=None, overwrite_x=False, workers=None, *, plan=None)[source]#
Compute the 2-D inverse discrete Fourier Transform.
This function computes the inverse of the 2-D discrete Fourier Transform over any number of axes in an M-D array by means of the Fast Fourier Transform (FFT). In other words,
ifft2(fft2(x)) == x
to within numerical accuracy. By default, the inverse transform is computed over the last two axes of the input array.The input, analogously to
ifft
, should be ordered in the same way as is returned byfft2
, i.e., it should have the term for zero frequency in the low-order corner of the two axes, the positive frequency terms in the first half of these axes, the term for the Nyquist frequency in the middle of the axes and the negative frequency terms in the second half of both axes, in order of decreasingly negative frequency.- Parameters:
- xarray_like
Input array, can be complex.
- ssequence of ints, optional
Shape (length of each axis) of the output (
s[0]
refers to axis 0,s[1]
to axis 1, etc.). This corresponds to n forifft(x, n)
. Along each axis, if the given shape is smaller than that of the input, the input is cropped. If it is larger, the input is padded with zeros. if s is not given, the shape of the input along the axes specified by axes is used. See notes for issue onifft
zero padding.- axessequence of ints, optional
Axes over which to compute the FFT. If not given, the last two axes are used.
- norm{“backward”, “ortho”, “forward”}, optional
Normalization mode (see
fft
). Default is “backward”.- overwrite_xbool, optional
If True, the contents of x can be destroyed; the default is False. See
fft
for more details.- workersint, optional
Maximum number of workers to use for parallel computation. If negative, the value wraps around from
os.cpu_count()
. Seefft
for more details.- planobject, optional
This argument is reserved for passing in a precomputed plan provided by downstream FFT vendors. It is currently not used in SciPy.
Added in version 1.5.0.
- Returns:
- outcomplex ndarray
The truncated or zero-padded input, transformed along the axes indicated by axes, or the last two axes if axes is not given.
- Raises:
- ValueError
If s and axes have different length, or axes not given and
len(s) != 2
.- IndexError
If an element of axes is larger than the number of axes of x.
See also
Notes
ifft2
is justifftn
with a different default for axes.See
ifftn
for details and a plotting example, andfft
for definition and conventions used.Zero-padding, analogously with
ifft
, is performed by appending zeros to the input along the specified dimension. Although this is the common approach, it might lead to surprising results. If another form of zero padding is desired, it must be performed beforeifft2
is called.Examples
>>> import scipy.fft >>> import numpy as np >>> x = 4 * np.eye(4) >>> scipy.fft.ifft2(x) array([[1.+0.j, 0.+0.j, 0.+0.j, 0.+0.j], # may vary [0.+0.j, 0.+0.j, 0.+0.j, 1.+0.j], [0.+0.j, 0.+0.j, 1.+0.j, 0.+0.j], [0.+0.j, 1.+0.j, 0.+0.j, 0.+0.j]])