Patent ID: 7149354

Claim:
A method comprising: reading a plurality of image rows; reading a plurality of image columns; converting the image rows into a plurality of row gradient runs, a row gradient run being defined by the equation <x 1 , x 2 , y, z 1 , z 2 >=HRy, where x 1 is the coordinate of the beginning of the run, x 2 is the coordinate of the end of the run, y is the index of an image row, z 1 =ƒ (x 1 , y), and z 2 =ƒ (x 2 , y) for some scalar function ƒ; converting the image columns into a plurality of column gradient runs, a column gradient run being defined by the equation <y 1 , y 2 , x, z 1 , z 2 >=VRx, where y 1 is the coordinate of the beginning of the run, y 2 is the coordinate of the end of the run, x is the index of an image column, z 1 =ƒ(x, y 1 ), and z 2 =ƒ (x, y 2 ) for some scalar function ƒ; analyzing the row gradient runs to obtain at least one vertical edge; analyzing the column gradient runs to obtain at least one horizontal edge; and restoring a broken edge by a forced extension.