MATLAB: How does Matlab produce thin edges

Question

Im using sobel edge detection.

Here is the original image file if you have Matlab so you can take a look

How does Matlab, by itself manage to achieve very thin edges like this one (using just the Matlab's edge function with 'sobel' as parameter)

matlabsobel = edge(originalImage,'sobel')
imshow(matlabsobel)

but when I try to do sobel algorithm my own way, assuming the process is just the same..

originalImage = gaussianizedimage;
threshold = 60.5;
k = [1 2 1; 0 0 0; -1 -2 -1];
H = conv2(double(originalImage),k, 'same');
V = conv2(double(originalImage),k','same');
E = sqrt(H.*H + V.*V);
edgeImage = uint8((E > threshold) * 255);
imshow(edgeImage);
title('sobel algorithm')

Why is that its different? What is still lacking in my implementation to achieve Matlab's thin edges? Can anyone provide code to make it look/similar to Matlab native sobel edge detection?

Thanks

Answer 1

edge() takes a grayscale edge image like you'd get with imgradient(), and then thresholds it and skeletonizes the thresholded image, like you'd get with bwmorph(BW, 'Skel', inf).