H infty norm with Finite frequency control 2D

I'm trying to solve this 2D problem in matlab,

for a given matrices (2*2 dimension for example) using the following notations :

A frequency-domain representation of the matrix K

sigma=the maximum singular value of matrix K;

the fist axis is p and the secon axis is s where 1<p<4 and 1<s<4 and

K=[p-1 -2; -3 s-4]

how to ( compute and plot ) the surf that represnt for each pair (p,s) the ( sigma=the maximum singular value of matrix K) like this graph ( note that this graph is for a nother example ),

[Lewis Fer]

?????????