Tapering of 2D matrices

MATTAPER Tapering of 2D matrices.
[A,WINDOW] = MATTAPER(X,TF,W,S) performs gradual tapering by applying
either a student's t cumulative distribution function or a cosine
function to the four borders of the 2D matrix X.
For cosine: W is width of cosine in percent of width of X. S is unused.
For t-distribution: S defines the (integer) rate of decreasing border
values, and W the (integer) position of the half height of the applied
border window.

tf =
1: t-distribution
2: cosine

Example:
X = ones(60); % Uniform distribution
figure,surf(mattaper(X))

Written by Christian Lundmand Jensen
Date: 15th of February, 2013.

Update: 4th of April 2013
- Added cosine taper