1. An image processing method comprising: executing first-type processing on a first partial image data representing a partial image to generate a second partial image data; executing second-type processing on the second partial image data; and repeating the execution of the first and second-type processing on a plurality of partial images aligned to be adjacent to each other using a plurality of processing units, wherein a first-type process segment and a second-type process segment are executed parallel using the plurality of processing units, the first-type process segment relating to i-th partial image, and the second-type process segment relating to any of (i+1)-th to (i+p)-th partial images, where i is a positive integer, and p is a positive integer.