Optimum line density determining method and system

An optimum line density determining method comprising steps of:

• a) counting a number of pixels included in each set of pixels which pixels are of a predetermined color and are continuously arranged along a predetermined same direction, said pixels being ones included in input image information;
• said input image information consisting of lines of pixels, said lines being arranged in an original line density;
• and
• b) determining a high line density as an optimum line density if, as a result of the counting in said step a), it has been found that there are relatively many sets of predetermined-color pixels continuously arranged along the predetermined same direction, a number of pixels included in each set of said many sets of predetermined-color pixels continuously arranged along the predetermined same direction being small;
• determining a low line density as said optimum line density if, as a result of the counting in said step a), it has been found that there are relatively many sets of predetermined-color pixels continuously arranged along the predetermined same direction, a number of pixels included in each set of said many sets of predetermined-color pixels continuously arranged along the predetermined same direction being large;
• and determining said original line density as said optimum line density if a number of discrete pixels in a page of said input image information is not less than a predetermined value;
• said optimum line density being a line density into which said original line density of said image information is then converted.