Upon applying a demosaicing process to a photographic image, a display image is generated from the photographic image to which the demosaicing process is applied, and an instruction indicating a reference region on the display image, and an adjustment instruction of parameters for a development process are input. Then, an image region having a high correlation with the reference region is extracted as a similar region, and display images of the reference region and similar region are generated by applying the parameters for the development process to the photographic image before the demosaicing process, which corresponds to the reference region, and that before the demosaicing process, which corresponds to the similar region.