Image Processing Toolbox User's Guide |

**Computing the Frequency Response of a Filter**

The `freqz2`

function computes the frequency response for a two-dimensional filter. With no output arguments, `freqz2`

creates a mesh plot of the frequency response. For example, consider this FIR filter,

This command computes and displays the 64-by-64 point frequency response of `h`

.

**Frequency Response of a Two-Dimensional Filter
**

To obtain the frequency response matrix `H`

and the frequency point vectors `f1`

and `f2`

, use output arguments

`freqz2`

normalizes the frequencies `f1`

and `f2`

so that the value 1.0 corresponds to half the sampling frequency, or radians.

For a simple `m`

-by-`n`

response, as shown above, `freqz2`

uses the two-dimensional fast Fourier transform function `fft2`

. You can also specify vectors of arbitrary frequency points, but in this case `freqz2`

uses a slower algorithm.

See Fourier Transform for more information about the fast Fourier transform and its application to linear filtering and filter design.

Creating the Desired Frequency Response Matrix | Transforms |

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