%% Sobel

% Apply Sobel in vertical and horizontal directions
img = double (imread ('berndsface.png'));
folder = 'C:\Users\HP\Documents\Laboratory Matlab\Laboratory 25\';
h = fspecial ('sobel');
filteredImg1 = imfilter (img, h', 'replicate');
filteredImg2 = double (imfilter (img, h, 'replicate'));

%Threshold based on edge magnitude response
edgeSum = filteredImg1 .^2 + filteredImg2 .^2;
logEdgeSum = log (edgeSum + 1);
logEdgeSum = logEdgeSum / max (logEdgeSum (:));
bwEdge1 = edgeSum > 1600; % (4/3) ^2 times the value for Prewitt
bwEdge2 = edgeSum > 8000;
bwEdge3 = edgeSum > 12800;

% Show and save images
figure(4), clf;
subplot (2, 2, 1), imshow (logEdgeSum); title ('Edge Magnitude');
subplot (2, 2, 2), imshow (bwEdge1); title ('Magnitude > 1600');
subplot (2, 2, 3), imshow (bwEdge2); title ('Magnitude > 8000');
subplot (2, 2, 4), imshow (bwEdge3); title ('Magnitude > 128000');
imwrite (logEdgeSum,strcat(folder, 'Sobel_face_logEdgeSum.png'));
imwrite (bwEdge1,strcat(folder, 'Sobel_face_bwEdge1.png'));
imwrite (bwEdge2,strcat(folder, 'Sobel_face_bwEdge2.png'));
imwrite (bwEdge3,strcat(folder, 'Sobel_face_beEdge3.png'));