MATLAB Function Reference |

Two-dimensional discrete Fourier transform

**Syntax**

**Description**

```
Y = fft2(X)
```

returns the two-dimensional discrete Fourier transform (DFT) of `X`

, computed with a fast Fourier transform (FFT) algorithm. The result `Y`

is the same size as `X.`

```
Y = fft2(X,m,n)
```

truncates `X`

, or pads `X`

with zeros to create an `m`

-by-`n`

array before doing the transform. The result is `m`

-by-`n`

.

**Algorithm**

`fft2(X)`

can be simply computed as

This computes the one-dimensional DFT of each column `X`

, then of each row of the result. The execution time for `fft`

depends on the length of the transform. It is fastest for powers of two. It is almost as fast for lengths that have only small prime factors. It is typically several times slower for lengths that are prime or which have large prime factors.

**See Also**

fft | fftn |