A Lighting Normalization Method for Processing Face Images

A face image, normalization technology, applied in instruments, character and pattern recognition, computer parts and other directions, can solve problems such as loss of feature information, illumination invariant features, unfavorable face recognition, etc.

Inactive Publication Date: 2016-06-29
XIAN UNIV OF TECH
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AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a method for normalizing the illumination of human face images, so as to solve the problem of the existing illumination invariant feature extraction method, which causes a large loss of feature information during face recognition, which is not conducive to subsequent face recognition problem

Method used

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  • A Lighting Normalization Method for Processing Face Images
  • A Lighting Normalization Method for Processing Face Images
  • A Lighting Normalization Method for Processing Face Images

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0062] Step 1, set an actual face grayscale image affected by light as f(x,y), such as figure 2 As shown, its size is 80×80 pixels, and logarithmic transformation is performed on it to obtain

[0063] Step 2, calculate the shadow layer image

[0064] 2.1) Calculate the difference image of the face image f(x,y) obtained in step 1 in the x direction: That is, the difference between the gray value of the left and right adjacent pixels of the image in the horizontal direction;

[0065] 2.2) Calculate the face image obtained in step 1 Difference in the y direction: That is, the difference between the gray value of the upper and lower adjacent pixels of the image in the vertical direction;

[0066] 2.3) Calculate each element A of matrix A i,j Such as formula (1):

[0067] A i , j = - λ ...

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Abstract

The invention discloses an illumination normalization method for processing human face images, which is specifically implemented according to the following steps: read in the human face image to be processed and take logarithm of it; calculate the shadow layer image; calculate the reflective layer image and perform exponential transformation ; select the sample image and calculate its histogram; normalize the reflective layer image by using the histogram matching method to obtain the corrected image of the face image to be processed by the illumination normalization method. The feature information on the large-scale layer can be preserved by using the edge-preserving filter; the sample image in the visually optimal area is used, so that the mean and variance of the corrected reflection layer image can be in the visually optimal area, which is beneficial to the subsequent face The recognition system can improve the correct rate of face recognition, and solve the problem that the existing feature extraction method of invariant illumination causes a large loss of feature information during face recognition, which is not conducive to the subsequent face recognition.

Description

technical field [0001] The invention belongs to the technical field of digital image processing, and relates to an illumination normalization method for processing human face images. Background technique [0002] Face recognition under variable lighting conditions, such as shadows, overexposure, and underexposure, is a difficult problem in face recognition systems. In the past ten years, although many methods have been proposed, all of them are unsatisfactory, and most of them cannot be applied to actual needs. [0003] One type of method for lighting processing of face images under variable lighting conditions is to directly perform lighting correction, such as grayscale stretching, Gamma correction, histogram equalization, and histogram matching. These methods do not consider the image to be processed Therefore, it is difficult for such methods to obtain satisfactory processing results. Another method is illumination-invariant feature extraction, which regards the face i...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06K9/36
Inventor 张二虎陈万军牟永强
Owner XIAN UNIV OF TECH
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