A method of processing image data is disclosed. According to an embodiment of the present invention, the method, which obtains image data for printing the edge of a circular pad having a radius of R by forming ink blots having a radius of r in an overlapping manner, includes: setting a permissible pitch range as a distance between adjacent ink blots; arranging first image data to the edge of the pad, in an x-y coordinate system; generating second image data with a smaller radius than the first image data, the second image data sharing the center with the first image data; arranging a first base point on the second image data; selecting the first determination point on the second image data separated from the first base point; determining if a distance between the first base point and the first determination point is within the permissible pitch range; and storing a coordinate, located at a shortest distance from the first determination point, as print data.