Hello,
You can use imquantize function, where you must specify the levels as [10,36] so that it quantizes in to three levels ([0-10], [10-36], [36-255]). You can refer to the code below.
% Load the image
img = imread('img.jpg');
% Define the Region of interest(ROI) of image
roi = img(100:200, 150:450);
% Define the quantization ranges
ranges = [10 36];
% Quantize the ROI
quantized_roi = imquantize(roi, ranges);
% Display the original and quantized ROIs
figure;
subplot(1,2,1);
imshow(roi);
title('Original ROI');
subplot(1,2,2);
imshow(quantized_roi, []);
title('Quantized ROI');
