1. A method of automatically extracting a validity period of a driving license, the method comprising: receiving an image file of a vehicle driving license; extracting candidate contour regions from within the image file according to a contour extraction rule, and selecting from among the extracted candidate contour regions at least one candidate contour region containing an annual inspection validity period; extracting all character contours from within each selected candidate contour region; acquiring a smallest circumscribed rectangle of each character contour in the selected candidate contour region, and dividing image blocks bound by the acquired smallest circumscribed rectangles one by one into individual single-character blocks; sorting these single-character blocks according to their respective positions in the selected candidate contour region; recognizing a corresponding character of each single-character block; generating a character string representing the annual inspection validity period using the recognized characters based on the sorting; and extracting time data in the character string and taking the time data as the annual inspection validity period of the selected candidate contour region.