Stamp detecting device, stamp detecting method, letter processing apparatus and letter processing method

摘要

An image input section inputs an image of a letter P and stores the same into an image memory. A stamp detecting section detects a stamp by a luminance projection value based on the image of the letter stored in the image memory, determining that an area is not an external area of the stamp and determining the area as an internal area of the stamp if the length of the area is smaller than a stamp internal gap permissible threshold value used for determining a stamp internal gap even in a case where the area which is partly determined as an external area of the stamp is present in an area which is determined as the internal area of the stamp affixed to the letter P based on the thus derived projection value.