A server includes a generating unit which generates image data in a partial region of a displayed image on the screen; a type identifying unit configured to identify a type of a GUI component included in the region of the generated image data; a storage which stores compression property information for each GUI component type; a compression scheme deciding unit which decides a compression scheme based on compression property information corresponding to the GUI component type identified; a compression unit which compresses the generated image data with a decided compression scheme; a transmission unit which transmits the compressed data to the client terminal; an update frequency deciding unit which decides a update frequency of the compression property information in the storage for each type of the GUI component; and an updating unit which updates the compression property information with the update frequency decided for each type of the GUI component.