Method and device for allocating core points of finger prints
First Claim
Patent Images
1. A method for allocating a core point of a finger print in the form of a binary image constituted by a plurality of windows, comprising the following steps:
- (1) finding out ridge flows of said finger print--assigning a direction code to each of said windows of the binary image;
(2) correcting the ridge flows --correcting the direction codes in order to eliminate noises; and
(3) allocating the core point --allocating the core point in accordance with the corrected direction codes.
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Abstract
A method to automatically find out the actual position of the core point of a finger print by using the characteristic of the ridge flow of finger prints. This method comprises three parts: (1) ridge flow finding algorithm, (2) ridge flow correction algorithm and (3) core point allocation algorithm.
138 Citations
11 Claims
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1. A method for allocating a core point of a finger print in the form of a binary image constituted by a plurality of windows, comprising the following steps:
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(1) finding out ridge flows of said finger print--assigning a direction code to each of said windows of the binary image; (2) correcting the ridge flows --correcting the direction codes in order to eliminate noises; and (3) allocating the core point --allocating the core point in accordance with the corrected direction codes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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4. A method as claimed in claim 3 wherein said mask is one of the following:
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space="preserve" listing-type="tabular">__________________________________________________________________________-1 0 1 2 1 0 -1 -2 -1 0 -1 -2 -2 0 2 1 0 -1 0 0 0 1 0 -1 -1 0 1, 0 -1 -2, 1 2 1, or 2 1 1 __________________________________________________________________________each of which is associated with a particular orientation.
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5. A method as claimed in claim 2, wherein the step of calculation is to take a convolution operation on each of said windows with four 3×
- 3 masks and the step of decision gives the orientation of said each of the windows in accordance with the number of "0",s which are results of the convolution operation.
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6. A method as claimed in claim 1, wherein the step of correcting the ridge flow comprises the following steps:
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(1) checking --checking, for each one of said windows, the direction codes of the eight windows therearound and taking the code, of which the number is the largest, as a reference code; and (2) correcting --substituting the direction code of said window with the reference code if said direction code is different from the reference code.
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7. A method as claimed in claim 1, wherein the step of allocating the core point comprises the following steps:
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(1) searching --searching among the direction codes of said image for a particular area constituted by a selected code and substantially located at the upper part of said image; and (2) allocating --picking up the narrowest portion of said particular area as the core point.
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8. A method as claimed in claim 7, wherein said selected code is the code represents the horizontal extension of the ridge flow.
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9. A finger print processing apparatus comprising:
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(1) input means which inputs a binary image for processing; (2) coding means which divides said binary image into a plurality of windows and gives each of the windows a direction code according to a ridge flow thereof to form a distributions map of the direction codes of the windows; (3) allocating means which finds out a particular upper area of a selected code in said distribution map according to the direction codes and locates the narrowest portion of said upper area as the core point; and (4) processing means which takes operations on said binary image, taking the core point thereof as a reference point; characterized in that the coding means gives four types of direction codes for the orientations of east-west, southeast-northwest, south-north and northeast-southwest. - View Dependent Claims (10, 11)
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Specification