High-precision method for simultaneously estimating face image illumination parameter and de-illumination map
A face image and lighting parameter technology, applied in the field of computer vision and image processing, can solve the problems that cannot be established strictly, loss of estimation accuracy of the light map, and affect the recognition rate of the face recognition system, so as to improve the accuracy and improve the lighting Effect of redrawing quality, improving estimation accuracy
Inactive Publication Date: 2014-01-15
XI AN JIAOTONG UNIV
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However, in reality, the reflection coefficient of the face surface varies from point to point, and this assumption cannot be strictly established.
This approximate expression introduces inherent errors into the estimation of illumination parameters, and will directly lead to the loss of estimation accuracy of the de-illumination map, thereby affecting the recognition rate of the face recognition system.
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[0028] The present invention will be described in more detail below in conjunction with the accompanying drawings and embodiments.
[0029] The high-precision simultaneous estimation method of illumination parameters and de-illumination maps of face images uses the Lambert reflection model to model the imaging of face images. The model is shown in the following formula (1):
[0030] I(p)=ρ(p)n(p) T s(p) (1)
[0031] The face image I in formula (1) is expressed by multiplying the point-by-point reflection coefficient ρ reflecting the texture information on each surface point by the inner product of the normal vector n on the point and the light source vector s, p=1...P , represents each pixel in the image I whose total number of pixels is P; according to the illumination vector of a three-dimensional object in 3D space, this principle can be approximated by the linear combination of three independent point light sources, let s j , j=1...3 represents a set of linearly independ...
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The invention discloses a high-precision method for simultaneously estimating a face image illumination parameter and a de-illumination map. On the basis of the parametric illumination subspace frame of a quotient graph algorithm, an improved target function and a constraint condition thereof are proposed, each pixel potion of the face owns an independent reflection coefficient, the physical practicality of the face is more conformed, and the parameter estimation precision is improved. An EM-like iterative algorithm is designed to solve the target function, and therefore the purpose of simultaneously estimating the illumination parameter and the de-illumination map can be efficiently realized. Compared with the traditional quotient graph algorithm, the proposed improved algorithm has the advantage of improving the estimation precision of the face image illumination parameter and the de-illumination map, therefore the algorithm can be directly used for improving the redrawing quality for the face image illumination on the basis of the illumination parameter, and the accuracy of a face identification system on the basis of the de-illumination map can be improved.
Description
technical field [0001] The invention belongs to the technical field of computer vision and image processing, in particular to a method for simultaneously estimating illumination parameters and de-illumination maps of human face images with high precision. Background technique [0002] Illumination is an important factor affecting face imaging and face image composition. Changing and unknown lighting conditions are one of the difficulties in the realization of face image analysis, synthesis, and recognition technology. The existence of illumination differences between face images seriously restricts the existing human Performance of face recognition systems. Therefore, the demand for research on the lighting effect of face images comes first from the construction of a face recognition system that is more robust to lighting changes. In addition, face illumination estimation and redrawing technology is also very active in the field of computer graphics, and is widely used in v...
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IPC IPC(8): G06K9/62G06T7/20G06T7/586
Inventor 刘剑毅郑南宁刘跃虎马瑶
Owner XI AN JIAOTONG UNIV