Find a range in a matrix and rescale it

In a image, those in the range [120 230] are scaled into range [0 120].

How to do it? Thanks.

if (a>120/255) & (a<230/255)

a==0;

end

I tried something like this but it doesnt work. Thanks.

Answer 1

[KSSV]

Let A be your image:

A0 = A ;   % save for test 
idx = A >= 120 & A<= 230 ;  % get indices of required values 
val = A(idx) ;  % values 
val_rescale = rescale(val,0,120) ; % scale the values 
A(idx) = val_rescale ;   % replace 

[Ben Ma]

What does val use for ?

It seems it is not used again

[KSSV]

Typo error...val should be used in the function rescale. Edited the answer.

[Ben Ma]

Thanks a lot.