To further improve the embedding performance, the adaptive PEE embedding introduced in (4) is also taken into account. For given (a, b), based on pairwise PEE, we first derive the 2D modification mapping of the adaptive PEE embedding (4) (see the right figure of Fig. 3 for example). Then, also by 2D-PEH division, convert the divided triangle region into a rectangular by coordinate transformation. For illustration, the 2D-PEH division in the first quadrant is presented in the left figure of Fig. 7, and, for the lower-right triangle region (black points), each (x, y) in this region is transormed to (xr, yr) as