1. A computer program for use in a line scanning system, said line scanning system comprising: a scanner for scanning an image and generating image information representative of said image, said image information having background elements and image elements; storage connected to said scanner for storing said elements as they are received from said scanner, said storage storing said elements into said memory so as to preserve a record of the location of each of said elements in said image; a computer connected to said scanner and to said storage and controlled by said computer program, said computer program comprising: first programmed instructions responsive to said scanner for selecting a left-most image element from each of a plurality of selected horizontal line scans; second programmed instructions responsive to said first programmed instructions for listing the location in said image of each of said left-most image elements; third programmed instructions responsive to said second programmed instructions for generating a best-fit line through said listed locations of said left-most image elements; fourth programmed instructions responsive to said third programmed instructions for changing said record of said locations of said image elements so as to rotate said stored image through an angle which is the difference of the slope of said best-fit line from vertical.