Image threshold value question

Hello guys, Normally we set one value 'a', then we have [0 a]= black, [a 255]=white My question is, can we do it like this way, [0 a]=black, [a b]=white, [b 255]=black I hold you can understand my terrible description.

Answer 1

[Image Analyst]

Sure, just do two comparisons:

binaryImage = grayImage >= a & grayImage <= b;

Answer 2

[Thorsten]

 I = imread('cameraman.tif');
 a = 100; b = 150;
 ind = setdiff(find(I > a), find(I < b));
 B = logical(size(I));
 B(ind) = 1;