[Aim] To appropriately determine passband characteristics for suppressing a periodic pattern, such as a grid image, in a radiographic image including the periodic pattern.[Solution Means] A peak position (pf) and a peak width (pw) of a frequency spectrum corresponding to a periodic pattern are detected by performing, with respect to at least one direction, frequency analysis on an image signal representing an image including the periodic pattern. The passband characteristics (F) of a one-dimensional filter suppressing a spatial frequency component corresponding to the periodic pattern in the image signal are determined based on the detected peak position (pf) and the detected peak width (pw).
