6. The computer-implemented method of claim 4 , wherein each first candidate region is contained within a whole region of the content piece.
6. The computer-implemented method of claim 4 , wherein each first candidate region is contained within a whole region of the content piece. 7. The computer-implemented method of claim 6 , wherein the first proportionate size of each first candidate region corresponds to a ratio of a size of the first candidate region to a size of the whole region containing the first candidate region.