Method and apparatus for image processing

• US 5,825,924 A
• Filed: 11/25/1996
• Issued: 10/20/1998
• Est. Priority Date: 05/07/1993
• Status: Expired due to Fees

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Kobayashi, Tetsuji
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Do, Anh Hong
• Application Number:
  US08/757,960
• Time in Patent Office: 694 Days
• Field of Search: 382/125, 382/126, 382/218, 382/219, 382/209
• US Class Current: 382/219
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction
• CPC Class Codes: G06V 40/1365 Matching; Classification
• CPC Class Codes: G07C 9/37 using biometric data, e.g. fingerprints, iris scans or voice recognition

Abstract

The present invention provides an image processing apparatus and method comprising a memory for storing address information of a binary registered image. An original test image is converted into a binary test image so that the ratio of the total number of black pixels to the total number of black and white pixels lies within a predetermined range. The binary test image is aligned to the binary registered image in order to compare the two images. A degree of concordance between the binary test image and the binary registered image is determined if the comparison satisfies a predetermined condition of concordance. A degree of discordance between the binary test image and the binary registered image is determined if the comparison satisfies a predetermined condition of discordance. The binary test image is determined to originate from the same object as the binary registered image according to the degree of concordance and the degree of discordance between the two images.

Claims

1. An image processing apparatus having stored registered images, comprising:

means for determining whether a ratio of a total number of black pixels to a total number of black pixels and white pixels in an original test image is within a first predetermined range;

binary converting and fixing means for converting the original test image into a binary test image and for fixing said binary test image for comparison, said binary converting and fixing means reconverting and refixing until said original test image has said ratio within the first predetermined range;

memory means for storing said binary test image having said ratio within said first predetermined range and a binary converted one of said stored registered images, said one of said stored registered images being converted and fixed in the same manner as said test image;

means for aligning said binary test image with said binary registered image to compare said two binary images; and

means for comparing said two binary images to determine whether said binary test image is the same as said binary registered image, said binary test image having said ratio within said first predetermined range being used for comparison with said binary registered image by said comparing means.

2. An image processing apparatus according to claim 1, further comprising means for thinning said binary test image, the thinning being a narrowing of the width of black pixels of said binary test image so that a majority of the width of a black line in said original test image occupies a whole width of a black pixel, and said binary test image after thinning is used for comparison with said binary registered image.

3. An image processing apparatus according to claim 1, wherein the means for aligning said binary test image with said binary registered image includes means for moving at least one of the two binary images in one or more intervals in order to compare said two binary images, wherein each said one or more intervals is divided into a plurality of partial intervals, means for judging whether said binary test image satisfies a predetermined condition of concordance with said binary registered image in one of said partial intervals, means for successively displacing said one partial interval until said predetermined condition of concordance is satisfied, and means for judging said binary test image as originating from a same object as said binary registered image when said predetermined condition of concordance is satisfied.

4. An image processing apparatus according to claim 1, wherein the aligning means comprises:

means for converting, fixing, and thinning the one stored registered image into a thinned binary registered image; and

wherein the comparing means comprises;

means for judging whether a concordance between said binary test image and said thinned binary registered image satisfies a predetermined condition of a degree of concordance; and

means for judging whether said binary test image originates from a same object as said thinned binary registered image according to said degree of concordance and a degree of discordance in order to minimize recognition error.

5. An image processing apparatus according to claim 1, wherein the means for aligning said binary test image with said binary registered image includes:

means for moving at least one of the two binary images in one or more intervals in order to compare said two binary images, wherein each said one or more intervals is divided into a plurality of N partial intervals, and

means for judging whether said binary test image satisfies a predetermined condition of concordance with said binary registered image in one of said N partial intervals;

means for successively displacing said N partial intervals of an m-th (m is a positive number) order of said partial intervals;

means for judging that said binary test image originates from a same object as said binary registered image when said predetermined condition of concordance is satisfied prior to the m-th order of successive displacement; and

means for judging that said binary test image originates from a different object than said binary registered image when said predetermined condition of concordance is not satisfied until a successive displacement of the m-th order of said partial intervals, so as to carry out rapid comparison by said comparing means.

6. An image processing apparatus according to claim 1, wherein said means for comparing comprises:

means for judging concordance of a black pixel of said binary test image with a black pixel of said binary registered image, and

means for comparing pixels of said binary test image with pixels of said binary registered image, binary information of a pixel of said binary test image being concordant with binary information of a pixel of said binary registered image at a corresponding address when the binary information of each of said two pixels is equal to each other, or when the binary information of at least one of neighboring pixels around said binary test image is equal to said pixel of said binary registered image.

7. An image processing apparatus according to claim 1, further comprising:

means for obtaining a reverse image of said original test image and said stored registered image;

means for converting said reverse test image and said reverse registered image into a binary reversed test image and a binary reversed registered image, respectively, so that a ratio of black pixels to total pixels lies within the first predetermined range;

memory means for storing address information of black pixels of said binary reversed test image and said binary reversed registered image;

means for comparing said binary registered image with said binary test image for evaluating a first degree of concordance;

means for comparing the binary reversed test image with said binary reversed registered image to evaluate a second degree of concordance; and

means for determining that the original test image and said stored registered image originate from the same object if both said first and second degrees of concordance evaluation satisfy respective predetermined ranges.

8. An image processing apparatus having stored registered images, comprising:

means for determining whether a ratio of a total number of black pixels to a total number of black pixels and white pixels in an original test image is within a first predetermined range;

binary converting and fixing means for converting the original test image into a binary test image and for fixing said binary test image for comparison, said binary converting and fixing means reconverting and refixing until said original test image has said ratio within the first predetermined range, said binary converting and fixing means including

means for dividing said original test image into a plurality of partial regions,

means for obtaining an average brightness for each of the plurality of partial regions,

means for determining a threshold brightness value for each of the plurality of partial regions and for converting said original test image into a binary test image with reference to the threshold brightness value of each said partial region and regions neighboring each said partial region, and

means for obtaining the ratio of the total number of black pixels to the total number of black and white pixels, and for repeating said binary conversion of said original test image to a binary test image to change said threshold brightness value until said ratio of the total number of black pixels to the total number of black and white pixels is within the first predetermined range, the binary test image obtained after the repeated conversion being used for comparison with said binary registered image;

memory means for storing said binary test image having said ratio within said first predetermined range and a binary converted one of said stored registered images, said one of said stored registered images being converted and fixed in the same manner as said test image;

means for aligning said binary test image with said binary registered image to compare said two binary images; and

means for comparing said two binary images to determine whether said binary test image is the same as said binary registered image, said binary test image having said ratio within said first predetermined range being used for comparison with said binary registered image by said comparing means.

9. An image processing apparatus according to claim 8, wherein said memory means includes means for storing address information of said black pixels, including address information of representative black pixels in one of said partial regions,

wherein said address information includes an address of a black pixel, a bit to classify each pixel as black or white, and format identification data representing identification data of said partial regions, in order to minimize binary image storage volume in said memory means.

10. An image processing apparatus having stored registered images, comprising:

means for determining whether a ratio of a total number of black pixels to a total number of black pixels and white pixels in an original test image is within a first predetermined range;

binary converting and fixing means for converting the original test image into a binary test image and for fixing said binary test image for comparison, said binary converting and fixing means reconverting and refixing until said original test image has said ratio within the first predetermined range;

memory means for storing said binary test image having said ratio within said first predetermined range and a binary converted one of said stored registered images, said one of said stored registered images being converted and fixed in the same manner as said test image;

means for aligning said binary test image with said binary registered image to compare said two binary images;

means for discovering holes in said binary registered image; and

means for comparing said two binary images to determine whether said binary test image is the same as said binary registered image, said comparing means judging concordance of said binary test image and said binary registered image when both an address of a hole in said binary registered image and an address of a hole in the binary test image satisfy a predetermined relationship.