Patent ID: 8160368

Claim:
An image feature extraction method for extracting a feature of an image, comprising the step of performing k 2 (k is an arbitrary integer greater than or equal to 2) dividing process at least once on a given image so as to convert the given image into a multi-divided image, wherein the k 2 dividing process comprises the steps of: a) creating matrix T based on image matrix X; b) computing singular values σ 1 , σ 2 , . . . , σ k^2 of the matrix T, where σ 1 ≧σ 2 ≧ . . . ≧σ k^2 ; c) determining whether or not min j |σ j −σ j−1 |>ε, where ε shows a constant greater than or equal to machine epsilon; d) if the result of the determination in the step c) is “No” returning to the step c) subsequent to computing the singular values of enlarged matrix T α ; e) if the result of the determination in the step c) is “Yes”, obtaining U which satisfies T=USV T , where S=diag (σ 1 , σ 2 , . . . , σ k^2 ), U is an orthogonal matrix and V is an orthogonal matrix; f) obtaining matrix T 1 =U T T; and g) creating image matrix X 1 based on matrix T 1 , wherein the computing the singular values of the enlarged matrix T α in the step d) comprises the steps of: creating enlarged matrix T α based on matrix T and a frame added to at least a portion of at least one side of image matrix X, the frame having a size of at least k pixels and k pixels; and computing singular values σ 1 , σ 2 , . . . , σ k^2 of the enlarged matrix T α , where σ 1 ≧σ 2 ≧ . . . ≧σ k^2 .