1. An image processing apparatus, comprising: a fetcher which fetches an object scene image; a first adjuster which adjusts a tonality of the object scene image fetched by said fetcher, corresponding to a property of a display device; an object-scene-image outputter which outputs the object scene image having the tonality adjusted by said first adjuster, toward the display device; a second adjuster which adjusts the tonality of the object scene image fetched by said fetcher, in parallel with the adjusting process of said first adjuster; and a first searcher which searches for an object image that coincides with a registered object image from the object scene image having the tonality adjusted by said second adjuster.