Method and device for calculating line distance

A device for calculating a line distance of a fingerprint, comprising:

• a gray processing module configured to obtain an original image and to perform grayscale processing to generate a grayscale image;
• a generating module configured to generate a radical image and a tangential image according to the grayscale image;
• a smoothing module configured to perform filtering on the grayscale image according to the tangential image to generate a smoothened image and to convert the smoothened image into a binary image;
• a block processing module configured to divide the binary image into blocks and to determine a radical direction of a center point of each block according to the radical image;
• a sub-pixel calculating module configured to traverse pixels in the radical direction of the center point of each block to calculate a number of times pixel values of two adjacent pixels within the each block change between a first pixel value and a second pixel value, and to calculate a coordinate and sub-pixel value of a boundary point corresponding to a changing point, wherein the first pixel value is a pixel value of a pixel of a ridge line, and the second pixel value is a pixel value of a pixel of a valley line;
• and
• a line distance generating module configured to generate the line distance according to the number of times the pixel values of two adjacent pixels within the each block change between the first pixel value and the second pixel value, and according to the coordinate and the sub-pixel value of the boundary point corresponding to the changing-point.

A non-transitory computer-readable medium having computer program for, when being executed by a processor, performing a method for calculating a line distance of a fingerprint, the method comprising:

• obtaining an original image and performing grayscale processing to generate a grayscale image;
• generating a radical image and a tangential image according to the grayscale image;
• performing filtering on the grayscale image according to the tangential image to generate a smoothened image and converting the smoothened image into a binary image;
• dividing the binary image into blocks and determining a radical direction of a center point of each block according to the radical image;
• traversing pixels in the radical direction of the center point of each block to calculate a number of times pixel values of two adjacent pixels within the each block change between a first pixel value and a second pixel value, and to calculate a coordinate and sub-pixel value of a boundary point corresponding to a changing-point, wherein the first pixel value is a pixel value of a pixel of a ridge line, and the second pixel value is a pixel value of a pixel of a valley line;
• and
• generating the line distance according to the number of times the pixel values of two adjacent pixels within the each block change between the first pixel value and the second pixel value, and according to the coordinate and the sub-pixel value of the boundary point corresponding to the changing-point.