maxhessiannorm

Read and display an image that contains tubular threads of varying thicknesses.

I = imread("threads.png");
imshow(I)

Calculate the maximum of the Frobenius norm of the Hessian of the image, with tubular thickness set to seven pixels.

C = maxhessiannorm(I,7);

Create an enhanced version of the image highlighting threads seven pixels thick. Use a structure sensitivity threshold equal to half of the maximum of the Frobenius norm of the Hessian. In the image, threads show up dark against a light background, so specify the object polarity as "dark". Display the enhanced image.

J = fibermetric(I,7,ObjectPolarity="dark",StructureSensitivity=0.5*C); 
imshow(J)
title("Enhanced Tubular Structures 7 Pixels Thick")

Threshold the enhanced image to create a binary mask containing only the threads with the specified thickness.

BW = imbinarize(J);

Display the mask over the original image using the labeloverlay function. The overlay has a blue tint where the mask is true, meaning those threads have the specified thickness.

maskl = labeloverlay(I,BW);
imshow(maskl)
title("Detected Tubular Structures 7 Pixels Thick")