Illustration of the process of extracting a BP region in four steps. Panel a: AIA 193 Å example BP #149 on 01 January 2020 at 01:59:59 UT. Panel b: binary mask showing the region that exceeds the median of the whole weighted Gaussian data cube by 6 sigmas. Panel c: binary mask showing the previous region but expanded to include pixels down to 3 sigmas. Panel d: binary mask with holes filled using morphological filtering. This is the final BP area. The temporal evolution of the BP in panel a is available as an online movie.