I've added the output at the end of the blog post for that image... check it out!
This algorithm works pretty well for billboards in urban settings as well -- since the photos come with the units outlined.
This algorithm works pretty well for billboards in urban settings as well -- since the photos come with the units outlined.
It is fairly straightforward to detect a billboard in a random nature scene; look for straight lines and intersections of them. Most (all?) billboards are also horizontal.
It is quite another thing to detect billboards in an urban setting.