y = gauss2 (xsigma, ysigma, kx, ky)
Gauss2(xsigma,ysigma,kx,ky) -- Generate a 2D gaussian envelope with peak=1 xsigma -- standard deviation in X ysigma -- standard deviation in Y kx -- number of sigmas to generate in X direction [6] ky -- number of sigmas to generate in Y direction [kx]