What kind of edge detection use paint.net? What kind of edge detection is used Paint.NET program? It allows me to choose the angle of the edge not like the one used by opencv (Canny).

Here an example:
The edges doesn't have single pixel width, so it's probably not canny (no non-maxima supression). Could be a simple high-pass filter, whose pass-band is masked out in the Fourier domain in specific angles.