JP2901221B2 - Fingerprint input method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint input method for performing fingerprint collation or the like.

[0002]

2. Description of the Related Art Fingerprint collation is determined by matching with a fingerprint registered in advance. The fingerprint registered in advance is
Although registered at correct input angles in the horizontal and vertical directions, it is rare that a fingerprint image is input at a correct angle when inputting fingerprint data. Therefore, when performing fingerprint collation, it is necessary to correct the angle of the fingerprint input.However, there is no fingerprint input method for easily correcting the input angle electronically. The installation angle itself was regulated.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and provides a fingerprint input method for correcting the angle of an input fingerprint image by a simple method. The purpose is to:

[0004]

In order to achieve the above object, a fingerprint input method according to the present invention inputs a fingerprint image including two touching fingers and binarizes, contracts, and expands the two fingers to obtain two fingers. Is extracted, the tangent is thinned, a straight line between the pixels having the maximum value and the minimum value at the Y coordinate or the X coordinate of the thinned image is obtained, and the angle of the fingerprint input image is set so that the straight line becomes vertical. Is corrected.

[0005]

According to the fingerprint input method according to the present invention, a tangent of a finger can be extracted by inputting a fingerprint image including two touching fingers and binarizing, contracting, and expanding the finger. A tangent can be obtained as a straight line from the maximum and minimum values of the Y coordinate.

[0006]

Next, an embodiment of a fingerprint input method according to the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for implementing the present invention. FIG. 5 is a block diagram of an apparatus for practicing the present invention. This apparatus includes, for example, a central processing unit CPU, an image processing unit IPU, and an image memory IM.
The central processing unit CPU, the image processing unit IPU and the image memory IM are connected via a system bus SB, and the image processing unit and the image memory IM are connected by a local bus LB.

First, a fingerprint image including two touching fingers is input from an input device (not shown) (step 1-1), and registered in the image memory IM (step 1-2). Next, an input image is transferred from the image memory IM via the local bus LB in accordance with an instruction from the central processing unit CPU.
Send to The image processing unit IPU binarizes the input image as shown in FIG. 2 (step 1-3), and then performs a contraction process on the binary image (step 1-4). Here, the contraction process is a process of converting a boundary pixel into a background pixel. Since the tangent line of the two fingers is thicker than the joint line and the fingerprint, the tangent pixel of the two fingers remains to the end even after the contraction processing. next,
The remaining pixels are subjected to a predetermined number of expansion processes (step 1-5), and only the tangents of the two fingers are extracted.
Here, the expansion processing is processing for converting a background pixel adjacent to a boundary pixel into a graphic pixel.

Next, as shown in FIG. 3, the image subjected to the expansion processing is subjected to thinning processing (step 1-6). As a result, the approximate center line of the tangent can be obtained. Pixel (Ymax) having the maximum value of the Y coordinate in this thinned image
Alternatively, the central processing unit CPU calculates and extracts the pixel (Xmin) having the minimum value of the X coordinate and the pixel (Ymin) having the minimum value or the pixel (Xmax) having the maximum value (step 1-7). That is, these two pixels are the uppermost or leftmost part and the lowermost or rightmost part of the tangent line of the two fingers.

Next, as shown in FIG. 4, a straight line L between the two pixels is determined (step 1-8), and the straight line L is set so as to be parallel to the Y axis or perpendicular to the X axis. For example, the central processing unit CPU calculates an angle at which the fingerprint image is rotated around a pixel having the maximum value of the Y-axis (the minimum value of the X-axis) in the thin line figure, that is, the intersection angle θ between the straight line L and the Y-axis. (Step 1-9). Next, step 1
The angle of the input image is corrected by rotating all the pixels of the image registered at -2 by θ (step 1-10). As a result, an appropriate fingerprint input image is secured.

[0010]

As described above, according to the present invention, the contact 2
A fingerprint image including two fingers is input, binarized, contracted, and expanded to extract tangents of the two fingers, and thin the tangents,
A straight line between pixels having a maximum value (minimum value) and a minimum value (maximum value) at the Y coordinate or the X coordinate of the thinned image is obtained, and the angle of the fingerprint input image is determined so that the straight line is in a predetermined angle state. Since the correction is performed, the angle of the input fingerprint image can be corrected by a simple method, and for example, there is an effect that it is possible to assist in high-accuracy fingerprint collation.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of the present invention.

FIG. 2 is a conceptual diagram of a binary image.

FIG. 3 is a conceptual diagram of a thinned image.

FIG. 4 is a conceptual diagram for explaining angle correction by rotation.

FIG. 5 is a block diagram of an apparatus for implementing the present invention.

[Explanation of symbols]

 CPU Central processing unit IPU Image processing unit IM Image memory SB System bus LB Local bus X X-axis Y Y-axis Ymax Pixel having the maximum value of Y coordinate Ymin Pixel having the minimum value of Y coordinate Xmax Pixel having the maximum value of X coordinate Xmin Pixel having the minimum value of X coordinate L Straight line θ Intersection angle

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G06T 7/00

Claims (1)

(57) [Claims] 1. A fingerprint image including two touching fingers is input, and the input image is binarized.
The "shrinkage" process of converting the boundary pixels into background pixels is performed a predetermined number of times, thereby erasing pixels other than the tangents of the two fingers described above, and then converting the background pixels adjacent to the boundary pixels into graphic pixels. Is performed a predetermined number of times to express the tangent line clearly, then thin the tangent line, and determine the maximum and minimum points of the X coordinate or Y coordinate of the thinned image by using the tangent line. A fingerprint input method characterized in that a tangent is approximated to a straight line, and the angle of the fingerprint input is corrected based on the straight line, assuming the two ends.