A method for analyz ing the structu re of the white backgr ound in docu ment images is describ ed, along with applic ations to the proble m of isolati ng blocks of machine -printe d text. The appro ach is based on computa tionalgeometry algorith ms for off-li ne enumera tion of maximal white rectan gles and on-line rectan gle unific ation. These suppo rt a fast, simple, and gener al heuri stic ...