How change somme values on a matrix?

for example I have a "A" matrix , i want change somme pixel values inside him, like this example:

if true
  % code
if A<=20
A(value)=0;
else
A(value)=255; 
end

How can I do this?!

Answer 1

[Salaheddin Hosseinzadeh]

Hi Biza,

It sounds like you want to do thresholding.

A = A>20; % this makes A a logical matrix of 0 and 1, 1 is when A < 20
A = A.*255;

Anyway, this will do the job for you ;)