Density of each pixel is specified from a test pattern for measurement of density distribution, a density profile indicating distribution of the specified density for each pixel is acquired, and a pixel region including a “nozzle of interest” having a certain density difference or more from surrounding pixels and pixels on both sides thereof is extracted as a nozzle region of interest from the acquired density profile. Filters B to E, other than a filter A to be applied for density smoothing processing of pixels that do not belong to the nozzle region of interest, are applied for the density smoothing processing of the pixels in the nozzle region of interest, to generate a profile of a density correction value for eliminating a density difference between respective pixels based on the density profile after the smoothing processing.