fwind2() - Image Processing

Use fwind2 to design two-dimensional FIR
filters using the window method. fwind2 uses a
two-dimensional window specification to design a two-dimensional FIR
filter based on the desired frequency response Hd. fwind2 works
with two-dimensional windows; use fwind1 to work
with one-dimensional windows.h = fwind2(Hd, win) produces
the two-dimensional FIR filter h using an inverse
Fourier transform of the desired frequency response Hd and
multiplication by the window win. Hd is
a matrix containing the desired frequency response at equally spaced
points in the Cartesian plane. fwind2 returns h as
a computational molecule, which is the appropriate form to use with filter2. h is
the same size as win.For accurate results, use frequency points returned by freqspace to
create Hd. (See the entry for freqspace for
more information.)h = fwind2(f1, f2, Hd, win) lets
you specify the desired frequency response Hd at
arbitrary frequencies (f1 and f2)
along the x- and y-axes.
The frequency vectors f1 and f2 should
be in the range -1.0 to 1.0, where 1.0 corresponds to half the sampling
frequency, or π radians. h is the same size
as win.

Syntax

h = fwind2(Hd, win)h = fwind2(f1, f2, Hd, win)

Example

[f1,f2] = freqspace(21,'meshgrid');
Hd = ones(21); 
r = sqrt(f1.^2 + f2.^2);
Hd((r<0.1)|(r>0.5)) = 0;
colormap(jet(64))
mesh(f1,f2,Hd)

Output / Return Value

Limitations

Alternatives / See Also

Reference