Display image data for displaying images on a screen, and when display image data that has undergone specified gradation conversion is received, the characteristics of the output brightness displayed on the screen is checked. In the area for which the output brightness of the display image data is convex at the bottom in relation to the image data gradation values, the display image data gradation values are corrected so as to have a roughly linear relationship between the gradation values and the output brightness. Printing image data is generated based on the post-correction image data and an image is printed. In the area for which the output brightness bottom is convex, by performing this kind of correction, it is possible to print an image with an impression closer to the display on the screen. As a result, it is possible to print images on the monitor screen easily and without losing the impression received from the image displayed on the monitor screen.