1. An image processing method for extracting outline vectors of an input image from the image, comprising: the step of inputting the image divided into a plurality of stripe-shaped images; the outline extraction step of extracting outline vectors from each of the stripe-shaped images; and the smoothing step of smoothing the extracted outline vectors of each of the stripe-shaped images, wherein the smoothing step is performed excluding, from vectors to be smoothed near a boundary between the two adjacent stripe-shaped images, coordinate positions of significant outline vectors connected between two adjacent stripe-shaped images.