Patent ID: 7620260

Claim:
A line thinning method for a grayscale digital image of pixels, including the steps of: employing a processor for: (a) for a pixel in a sequence of pixels in the input image stored in a memory, locating a segment of the sequence including the pixel and neighboring pixels; (b) determining the local characteristics of the segment based on the characteristics of the pixels therein, said determining including determining an estimated derivative d and determining each refined derivative d′ from each derivative d for each pixel in a set f of N pixels {f[ 0 ], f[ 1 ], . . . , f[N−1]}, as: d ′ ⁡ [ x ] = { d ⁡ [ x ] if ⁢ ⁢  d ⁡ [ x ]  > THR ; 0 otherwise ⁢ ⁢ ⁢ for ⁢ ⁢ 0 ≤ x ≤ N - 1 wherein THR represents a threshold value; and (c) performing a thinning operation on the pixel based on the local characteristics of the segment by adjusting a grayscale value of the pixel.