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2-D FIR filter using 2-D window method

The `fwind2`

function designs 2-D FIR filters using the
window method. `fwind2`

uses a 2-D window specification to design a
2-D FIR filter based on the desired frequency response. `fwind2`

works
with 2-D windows only. Use `fwind1`

to create a 2-D FIR filter from a
1-D window.

You can apply the 2-D FIR filter to images by using the `filter2`

function.

`fwind2`

computes `h`

using an inverse Fourier
transform and multiplication by the two-dimensional window
`win`

.

$${h}_{d}({n}_{1},{n}_{2})=\frac{1}{{\left(2\pi \right)}^{2}}{\displaystyle {\int}_{-\pi}^{\pi}{\displaystyle {\int}_{-\pi}^{\pi}{H}_{d}({\omega}_{1},{\omega}_{2}){e}^{j{\omega}_{1}{n}_{1}}{e}^{j{\omega}_{2}{n}_{2}}d{\omega}_{1}d{\omega}_{2}}}$$

$$h({n}_{1},{n}_{2})={h}_{d}({n}_{1},{n}_{2})w({n}_{1},{n}_{2})$$

[1] Lim, Jae S., *Two-Dimensional Signal and Image
Processing*, Englewood Cliffs, NJ, Prentice Hall, 1990, pp.
202-213.