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# freqz2() - Image Processing

```[H, f1, f2] = freqz2(h, n1, n2) returns H,
the n2-by-n1 frequency response
of h, and the frequency vectors f1 (of
length n1) and f2 (of length n2). h is
a two-dimensional FIR filter, in the form of a computational molecule. f1 and f2 are
returned as normalized frequencies in the range -1.0 to 1.0, where
1.0 corresponds to half the sampling frequency, or π radians.[H, f1, f2] = freqz2(h, [n2 n1]) returns
the same result returned by  [H,f1,f2] = freqz2(h,n1,n2).[H, f1, f2] = freqz2(h) uses [n2
n1] = [64 64].[H, f1, f2] = freqz2(h, f1, f2) returns
the frequency response for the FIR filter h at
frequency values in f1 and f2.
These frequency values must be in the range -1.0 to 1.0, where 1.0
corresponds to half the sampling frequency, or π radians.[...] = freqz2(h,...,[dx dy]) uses [dx
dy] to override the intersample spacing in h. dx determines
the spacing for the x dimension and dy determines
the spacing for the y dimension. The default
spacing is 0.5, which corresponds to a sampling frequency of 2.0.[...] = freqz2(h,...,dx) uses dx to
determine the intersample spacing in both dimensions.freqz2(...)produces a mesh plot of the
two-dimensional magnitude frequency response when no output arguments
are specified.```

### Syntax

`[H, f1, f2] = freqz2(h, n1, n2)[H, f1, f2] = freqz2(h, [n2 n1])[H, f1, f2] = freqz2(h)[H, f1, f2] = freqz2(h, f1, f2)[...] = freqz2(h,...,[dx dy])[...] = freqz2(h,...,dx)freqz2(...)`

### Example

```Hd = zeros(16,16);
Hd(5:12,5:12) = 1;
Hd(7:10,7:10) = 0;
h = fwind1(Hd,bartlett(16));
colormap(jet(64))
freqz2(h,[32 32]); axis ([-1 1 -1 1 0 1])```