Edge detection : How can i get the outlines of an unfinished shapes ?

Hello ! For the needed of a project I would like to know if it's possible to get the outlines of this shape :

Expected :

The quality is pretty bad but I can not have better. I have already used a Canny filter but I only get the detection of a few pixels. If anyone has an idea, I'm interested !

Thank you

[jonas]

Even if you got the canny filter to work, you would probably end up with two disconnected lines on the top segment. The middle part is more or less indistinguishable from the background.

If you only had a single segment you could binarize and fit a line through the blobs.