Fundamental techniques and commonly employed algorithms for image manipulation of endoscopic images were reviewed, but only in a few instances was any novel information obtained. New software was recently developed for medium-frequency band enhancement: From the correlation distribution of image data in the RGB color space (distribution 1), only those data components depicting the fine structure patterns were extracted. The correlation distribution of the latter components was subsequently studied in the same space (distribution 2); the original image data were so processed that distribution 1 would be enhanced along the axis of greatest variation seen in distribution 2. This algorithm of image processing was successful in detecting minute surface structures of the mucosa hidden by the overlying mucus in the original images. It seems to be the first successful algorithm of image processing that obtained specific effects of enhancement without simultaneous noise enhancement.