Detect contour of solid region

In an article about contour extraction and compression of Andrzej Dziech, there are many methods to export contour of image.



In my case, I implement a contour extraction from a solid region.

Here the code :

Reference:
Contour Extraction and Compression-Selected Topics. Andrzej Dziech, AGH Universisty of Science and Technology, Telecommunication Dept., Cracow, Poland