1. An image processing apparatus comprising: a display unit to display image data; a range specifying unit to allow a user to specify a range of the image data displayed on the display unit; a characteristic extracting unit to extract, as a representative characteristic of the image data, partial data from image data within the range specified by the user; a storing unit to store the extracted partial data as the representative characteristic associated with the image data; and a display controlling unit to control displaying the partial associated with the image data when retrieving the image data for displaying the image data on the display unit, wherein the characteristic extracting unit extracts coupled components of pixels different from pixels of a background color in the specified range, integrates adjacent coupled components, and extracts the integrated components having the largest area to thereby extract the partial data corresponding to the largest area.