Image analysis – Image transformation or preprocessing
Patent
1992-10-28
1998-05-26
Chin, Wellington
Image analysis
Image transformation or preprocessing
382185, G06K 936, G06K 962
Patent
active
057579792
ABSTRACT:
A method for nonlinear normalization of an image, which performs pre-processing for computing the correlation between an unknown pattern and a reference pattern. A local spatial density function .rho.(X.sub.i, Y.sub.j) (i=1-I, j=1-J) is calculated from a two-dimensional pattern f(X.sub.i, Y.sub.j) which is obtained by sampling the unknown pattern at a sampling interval .gamma.. The spatial density function .rho.(X.sub.i, Y.sub.j) is obtained as the product of reciprocals of line pitches in both the X and Y directions. An x-direction cumulative function hx(X.sub.i) and a y-direction cumulative function hy(Y.sub.j) are computed by successively adding the space density function .rho.(X.sub.i, Y.sub.j). New sampling points (X.sub.i, Y.sub.j) are computed in such a fashion that new sampling intervals (.delta.i, .epsilon.j), defined as intervals between two adjacent points of the new sampling points (X.sub.i, Y.sub.j), satisfy the condition that a product between the cumulative function hx(X.sub.i) and .delta.i takes a first fixed value, and a product between the cumulative function hy(Y.sub.j) and .epsilon.j takes a second fixed value. The normalized sampled values at the new sampling points (X.sub.i, Y.sub.j) are obtained by resampling the unknown pattern or by performing a computation on the two dimensional pattern f(X.sub.i, Y.sub.j).
REFERENCES:
patent: 5033097 (1991-07-01), Nakamura
patent: 5138668 (1992-08-01), Abe
H. Yamada et al., "Line Density Equalization", The Journal of the Institute of Electronic Engineers of Japan, vol. J67-D, No. 11, Nov. 1984, pp. 1379-1383.
H. Yamada et al., "An Improvement of Nonlinear Normalization Method", The Report of the Institute of Electronics and Communication Engineers of Japan D-439. 1988, pp. 1-182.
Jun Tsukumo, "Nonlinear Normalization for Handprinted Chinese Character Recognition", Report of the Institute of Electronic, Information and Communication Engineers of Japan, 1987, pp. 1-68.
Hongo Yasuo
Yoshida Atsushi
Chin Wellington
Corrielus Jean B.
Fuji Electric & Co., Ltd.
Fujifacom Corporation
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