1. An image processing mask creating method comprising: calculating cluster energy of each point in an image processing mask; ranking points in ascending order or descending order on the basis of calculated cluster energy values; and allocating threshold values to the points in the image processing mask on the basis of the ranks as the process result of the ranking, wherein the cluster energy is defined as the sum of interaction values f r (∥x−y∥) having the distance ∥x−y∥ between a target point x and a point y belonging to a cluster not including the target point x as a parameter.