Interactive image query system using progressive transmission

There is a growing need for people to browse through files of images such as satellite or medical photos, to determine which ones warrant further examination. Users located at some distance from the image archive often must use slow transmission links such as telephone lines. If an image is scanned out line-by-line, top-to-bottom, the user must often wait too long to determine whether the image is of any use. Using the Progressive Transmission Method, however, images are encoded so that during transmission the entire display shows a rough version of the image in 'fat pixels'. If the user wishes to see more detail, additional data is sent and used to refine these pixels, until the exact original image is seen. We report here on extensions of this method to the rich color imagery found in remote-sensing applications. A significant advance is the elimination of unworkably large look-up tables by using a single simple algorithm for performing the required encoding and decoding operations. The method is conceptualized in a 'transmission cone' context which assists a user in interacting with the system. The user can roam over large images, zoom to various levels of resolution, and cause specified subregions of interest in the image to fill in to full resolution, at a tremendous saving in time.