how to calculate the distance between 2 matrix (without counting the number of 255)?

A = 255 0  135   
    91 255 255
    3  21  255

B = 11 0 135
    91 21 97
    3 21 218

E_distance = sqrt(sum((A-B).^2)); E_distance = 375

But I want to get the E_distance = 0. When the number is 255, don't need to calculate the distance between 2 matrix (direct skip). A & B become:

A =     0  135         
    91     
    3  21 

B =     0  135         
    91     
    3  21

When apply E_distance can get 0.

How to do? Please help me. Thanks

Answer 1

[KSSV]

A = [255 0  135   
    91 255 255
    3  21  255] ;
B = [11 0 135
    91 21 97
    3 21 218] ;
A0 = A ;
A(A0==255) = [] ;
B(A0==255) = [] ;
E_distance = sqrt(sum((A-B).^2));