how to change 8 - gray level to 32 gray level (GLCM)

i want to change 8 gray level to 32 gray level, because if i use 8-level the result is like this image

so i want to try use 32 level in my glcm

I = imread('001 A.png');
gray = rgb2gray(I);
offsets = [0 1;-1 1;-1 0;-1 -1];
[GLCMS,SI] = graycomatrix(gray,'Of', offsets);  
stats = graycoprops(GLCMS,{'contrast','homogeneity','correlation','energy'});
imshow(gray);

this is image i used

thank you before