Rmagick find_similar_region

Hi folks,

Just wondering if anyone could shed some light on the
find_similar_region method of rmagick as I'm hoping to find something
similar to use in VB.Net (I know, boo hiss, lol). Is this method a
native rmagick method or is it derived from ImageMagick/something else?

Any insights would be greatly appreciated :o)
Thanks very much,
Becky