To improve specification precision for a license plate position by deciding the license plate position according to information in a feature dictionary containing information regarding numerals thermselves.
A 1st feature dictionary 15a contains values D, obtained by adding respective pixel values of binary images of respective numbers, as data. The position D of a pixel position which appears frequently in a number image becomes large and the value D of a pixel position which do not appear frequently becomes small. A 2nd feature dictionary 15b contains pixel data obtained by inverting white pixels and black pixels. A secondary decision part 15 calculates the product sum arithmetic value A1 of an image of a character candidate image area and the addition value D of the 1st feature dictionary 15a. Further, the decision part 15 calculates the product sum arithmetic value A2 of the image of the character candidate image area and the addition value of the 2nd feature dictionary 15b. The secondary decision part 15 decides that the object character candidate image area is a number when the ratio A1/A2 exceeds a specific threshold value.
AMAMOTO NAOHIRO
KUNO YUJI
ICHII HIDESATO
