Two dimensional window generator (2D window)

This function creates a two-dimentional window that can be used for a matrix or image using MATLAB built-in 1D window function.

Usage: w = window2(r, c, w_type);
r: number of rows of the window you want to generate
c: number of columns
w_type: window type

Options are listed below (same with 1D built in function)
@bartlett - Bartlett window.
@barthannwin - Modified Bartlett-Hanning window.
@blackman - Blackman window.
@blackmanharris - Minimum 4-term Blackman-Harris window.
@bohmanwin - Bohman window.
@chebwin - Chebyshev window.
@flattopwin - Flat Top window.
@gausswin - Gaussian window.
@hamming - Hamming window.
@hann - Hann window.
@kaiser - Kaiser window.
@nuttallwin - Nuttall defined minimum 4-term Blackman-Harris window.
@parzenwin - Parzen (de la Valle-Poussin) window.
@rectwin - Rectangular window.
@taylorwin - Taylor window.
@tukeywin - Tukey window.
@triang - Triangular window.

-Example:
To compute windowed 2D FFT
[r,c]=size(img);
w=window2(r,c,@hamming);
fft2(img.*w);

Note: NOT using rotational symmetric convention

Disi A --- May,16, 2013
adis@mit.edu