This function bwmorph(Img,'skel',Inf) return the skeleton of a binary image.
What I'm looking for is the algorithm used by this function to do it manualy ?
If you want to see the actual code within a function in MATLAB, you can try using the TYPE command:
type bwmorph %# Command form
type('bwmorph.m') %# Function form
Keep in mind, this will not work on all MATLAB functions. You may get a message that says the function is a built-in function, in which case the code will not be displayed. You can also try opening the file in the MATLAB Editor using the EDIT command:
edit bwmorph.m %# Command form
edit('bwmorph.m') %# Function form