numpy.fft.ifft

numpy.fft.ifft2

# numpy.fft.fft2¶

`numpy.fft.``fft2`(a, s=None, axes=(-2, -1), norm=None)[source]

Compute the 2-dimensional discrete Fourier Transform

This function computes the n-dimensional discrete Fourier Transform over any axes in an M-dimensional array by means of the Fast Fourier Transform (FFT). By default, the transform is computed over the last two axes of the input array, i.e., a 2-dimensional FFT.

Parameters
aarray_like

Input array, can be complex

ssequence of ints, optional

Shape (length of each transformed axis) of the output (`s` refers to axis 0, `s` to axis 1, etc.). This corresponds to `n` for `fft(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.

axessequence of ints, optional

Axes over which to compute the FFT. If not given, the last two axes are used. A repeated index in axes means the transform over that axis is performed multiple times. A one-element sequence means that a one-dimensional FFT is performed.

norm{None, “ortho”}, optional

New in version 1.10.0.

Normalization mode (see `numpy.fft`). Default is None.

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 than the number of axes of a.

`numpy.fft`

Overall view of discrete Fourier transforms, with definitions and conventions used.

`ifft2`

The inverse two-dimensional FFT.

`fft`

The one-dimensional FFT.

`fftn`

The n-dimensional FFT.

`fftshift`

Shifts zero-frequency terms to the center of the array. For two-dimensional input, swaps first and third quadrants, and second and fourth quadrants.

Notes

`fft2` is just `fftn` with a different default for axes.

The output, analogously to `fft`, contains the term for zero frequency in the low-order corner of the transformed 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 the axes, in order of decreasingly negative frequency.

See `fftn` for details and a plotting example, and `numpy.fft` for definitions and conventions used.

Examples

```>>> a = np.mgrid[:5, :5]
>>> np.fft.fft2(a)
array([[ 50.  +0.j        ,   0.  +0.j        ,   0.  +0.j        , # may vary
0.  +0.j        ,   0.  +0.j        ],
[-12.5+17.20477401j,   0.  +0.j        ,   0.  +0.j        ,
0.  +0.j        ,   0.  +0.j        ],
[-12.5 +4.0614962j ,   0.  +0.j        ,   0.  +0.j        ,
0.  +0.j        ,   0.  +0.j        ],
[-12.5 -4.0614962j ,   0.  +0.j        ,   0.  +0.j        ,
0.  +0.j        ,   0.  +0.j        ],
[-12.5-17.20477401j,   0.  +0.j        ,   0.  +0.j        ,
0.  +0.j        ,   0.  +0.j        ]])
```