How does the algorithm behind contourc work?

Hello,

I am currently working on a project in wich I used the contourc combined with the C2xyz function from file exchange to generate a binary image, just showing the contours of the input image. Now I wanted to know how this contourc function works, how is the data produced. What method is used in this function? Is it kind of an edge detection, with threshold a threshold or something like this? I searched older questions related to this, but I could not find an answer.

Thanks for your help,

Nico.