A technique includes printing a first image including a plurality of edge pixels and a second image with a lower ratio of edges pixels than the first image and an average density equal to that of the first image and determining a value of a processing parameter so that the average densities of the first image and the second image match. The technique is configured to realize appropriate pre-print processing while preventing the average densities from being low due to the excessive pre-print processing or being high due to the insufficient pre-print processing.