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Low-quality fingerprint image direction field extraction method based on diffusion equation

A technology of fingerprint image and diffusion equation, which is applied in the direction of instruments, character and pattern recognition, computer parts, etc., can solve the problems of low fingerprint quality, unsatisfactory results, and inability to obtain reliable direction fields in the background area, etc.

Inactive Publication Date: 2012-07-25
XIDIAN UNIV
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AI Technical Summary

Problems solved by technology

[0011] The above algorithms have two common defects: 1) when the quality of the fingerprint is low, satisfactory results cannot be obtained; 2) the reliable direction field cannot be obtained in the background area

Method used

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  • Low-quality fingerprint image direction field extraction method based on diffusion equation
  • Low-quality fingerprint image direction field extraction method based on diffusion equation
  • Low-quality fingerprint image direction field extraction method based on diffusion equation

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Embodiment Construction

[0076] Attached below figure 1 The steps of the present invention are further described.

[0077] Step 1, input fingerprint image. Use I((x, y) to represent the gray value of the image at the coordinate point (x, y);

[0078] Step 2, calculate the gradient distribution of the input fingerprint image [I x , I y ], mass fraction Q(x, y) and crack mask M scar (x, y);

[0079] 2a) [I x , I y ] Use Sobel operator or Marr-Hildreth operator to calculate;

[0080] 2b) Construct a complex filter with symmetric properties:

[0081] h n = ( x + iy ) n · g , n ≥ ...

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Abstract

The invention discloses an fingerprint image direction field calculation method in an automatic fingerprint identification system. The fingerprint image direction field calculation method adopts a GVF-model based method and comprises the following steps: (1) inputting a fingerprint image; (2) calculating the gradient distribution, the quality score and the crack mask of the input fingerprint image; (3) judging the fingerprint quality, carrying out the step (4) if the fingerprint quality is bad, or carrying out the step (5) if the fingerprint quality is not bad; (4) actuating the crack mask and the initial GVF (gradient vector flow) field V0, and omitting the noise data in a crack region; (5) diffusing the initial GVF field V0 rapidly and smoothly, and taking the diffused GVF field as the Vcoarse; (6) calculating the distribution theta corse (x, y) of the direction field of the fingerprint by using the Vcoarse, detecting a singular point, and obtaining a singular region mask MSingulsr; (7) mending the Vcoarse of a singular region by using a GGVF (general gradient vector flow) model to obtain a final GVF field VFine; and (8) calculating the final direction field theta (x, y). The method overcomes the detects of poor low-quality background region image calculation effect of the prior art and achieves good low-quality fingerprint image calculation effect and the good result of obtaining the direction filed in the fingerprint background region.

Description

technical field [0001] The invention belongs to the technical field of digital image processing, and further relates to a calculation method of a fingerprint image direction field based on a diffusion equation model in an automatic fingerprint recognition system. The model can be used in image segmentation and edge detection. Background technique [0002] Orientation field estimation is a very important step in the fingerprint recognition process. Commonly used direction field extraction algorithms include gradient method, model method, filter method and other methods. [0003] The gradient method is the simplest and most widely used method for calculating the direction field. The phase angle of the gradient represents the direction in which the gray value changes the most in the image. Therefore, for a fingerprint image, the direction of the ridge line must be perpendicular to its gradient direction, and the direction distribution of the fingerprint can be obtained by an...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06K9/40G06K9/46
Inventor 曹凯陈茜庞辽军桂廷刘而云赵恒梁继民田捷
Owner XIDIAN UNIV
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