unsharp masking

%file = 'corners1.jpg';
%file = 'binary_blobs.jpg';
file='hallway.jpg'
rgb = imread(file);
rgb2 = imresize(rgb,0.5);
g = rgb2gray(rgb2);
im = im2double(g);
imshow(im);
clear rgb rgb2 g
file =

hallway.jpg

h = fspecial('disk',15);
zm = imfilter(im,h);

imshow(zm);
diff = im - zm;
bipolar_image(diff);
imshow((diff+1)/2);