12. The non-transitory computer readable storage medium of claim 11 , 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.
13. The non-transitory computer readable storage medium of claim 12 , wherein the content piece comprises a digitized image and the size of each first candidate region corresponds to a number of pixels in the first candidate region.