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Method of filtering an image with bar-shaped structures

A strip and image technology, applied in the direction of instruments, character and pattern recognition, computer parts, etc., can solve the problem of inaccurate combination, and achieve the effect of minimizing calculation time and simple structure.

Inactive Publication Date: 2008-02-27
NXP BV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to artifacts of the transforms (FFT and IFFT) that occur, the combination of the individual resulting blocks is therefore usually not precise enough if this is done without overlapping with neighboring blocks

Method used

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  • Method of filtering an image with bar-shaped structures
  • Method of filtering an image with bar-shaped structures

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Embodiment Construction

[0028] Accompanying drawing 1 shows the Gabor filtering of fingerprint image block 1, wherein, due to the limitation of the stipulation of the patent drawing, the effect of filtering itself is not shown. Block 1 is part of the fingerprint shown in Figure 3 and may have, for example, 32x32 image elements. However, other sizes and non-square, square blocks may also be used. With known Gabor filtering, two-dimensional filtering must be performed in the example shown in FIG. 1 , wherein the Gabor filter is arranged according to oblique and curvilinearly running fringes 2 .

[0029] In the method according to the invention, however, the mean direction of the stripes is determined by algorithms known per se, according to which block 1 is rotated in such a way that the mean direction of the stripes 2 is at right angles. The thus rotated block 3 is filtered by a filter 4 comprising a cosine function modulated by a Gaussian bell curve. The frequency of this cosine function is pre-mat...

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Abstract

In a method of filtering an image with bar-shaped structures by means of Gabor filters, which are formed in the spatial domain by a two-dimensional Gaussian bell-shaped curve on which a cosine function is superimposed in a main direction, the image is divided into tiles, a predominant direction of the bar-shaped structures is determined for each tile and the filtration is undertaken in such a way that one tile at a time is rotated until the predominant direction lies at right angles to the main direction of the Gabor filter, one filtration takes place in the main direction and another filtration takes place at right angles to this, and the filtered tile is rotated back again.

Description

technical field [0001] The invention relates to a method for filtering images with a strip structure by means of Gabor filters, which are composed of two-dimensional Liszian bell curves with superimposed cosine functions along the main direction in the spatial domain. formed in. Background technique [0002] An important field of application of the invention relates to the processing of images of skin impressions, especially fingerprint images. Starting from a grayscale image of the fingerprint (provided by a variety of commercially available sensors), enhancement of the groove structure involved will be achieved, while repair of any defects involved will be achieved. In a further step, this processed image is binarized and decisive features are extracted from the etched binary image. [0003] Gabor filters have proven their value for the strengthening and repair of (local) groove structures, since their principle is one of direction-dependent strengthening and frequency-d...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06K9/00
CPCG06K9/00067G06V40/1347
Inventor S·肖尔茨
Owner NXP BV
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