METHOD FOR BINARISATION OF IMAGES OF SYMBOLS ON A BANKNOTE BASED ON HISTOGRAM OF LENGTH OF BOUNDARIES Russian patent published in 2020 - IPC G06K9/00 

FIELD: data processing.

SUBSTANCE: invention relates to a method of binarisation of images of symbols on banknotes and can be used during authentication. To a halftone image of a symbol in a portion of a banknote to be binarized, a pixel of which is characterized by a brightness level, applying a threshold procedure using a process of forming a two-level image having one of two possible brightness levels with a predetermined binarisation threshold, plotting a histogram of the boundaries of said image, for which an ordered set of increasing brightness values, which are possible in a halftone image, is set, and for all values of brightness in the specified set, starting from the value following the least, the value of the corresponding cell of the histogram of the length of boundaries is set as an increment of the length of boundaries of the two-level image. Length of boundaries of the two-level image is counted as the sum of the lengths of the segments, each of which is a boundary segment of two adjacent pixels with different brightness levels, adding a component to account for the length of those sides of the pixels, which are located on the edge of the image, analyzing said histogram of the length of boundaries to find the final threshold of binarisation, when using which the result of binarisation contains continuous lines contained in the gray-scale image of the banknote area.

EFFECT: faster recognition of banknote symbols.

7 cl, 6 dwg