First, you can binarize the image and then use ‘bwmorph’ function to thicken the white lines present in the image.
Format of usage is as follows: bwmorph(img, ‘thicken’, n)
Here, ‘n’ is the number of times to perform the operations. You can control the thickening by controlling this parameter.
After thickening if you like to connect the unconnected pixels, then you can use ‘bwmorph(img, ‘bridge’)’ and then can use ‘imdilate’ function to enhance the connected line.
se = strel('line',10,180);
b = imdilate(b,se);
Hope this will help you.