Apparatus and method for verifying image by comparison with template image

• US 7,856,137 B2
• Filed: 06/22/2005
• Issued: 12/21/2010
• Est. Priority Date: 07/13/2004
• Status: Active Grant

• Current Assignee: Glory Limited
• Original Assignee: Glory Limited
• Inventors: Kameyama, Hirofumi, Yonezawa, Toru
• Primary Examiner(s): Mehta; Bhavesh M
• Assistant Examiner(s): Rashid; David P
• Application Number:
  US11/572,070
• Publication Number:
  US 20070165936A1
• Time in Patent Office: 2,008 Days
• Field of Search: 382/136
• US Class Current: 382/136
• CPC Class Codes: G06V 10/752 Contour matching
• CPC Class Codes: G06V 40/40 Spoof detection, e.g. liveness detection
• CPC Class Codes: G07D 5/005 Testing the surface pattern, e.g. relief

Abstract

A correlation value image is generated from an input image and a template image, and separated into a positive correlation value image and a negative correlation value image. The template image is separated into a positive template image and a negative template image. A plurality of positive-negative-separated correlation images are generated by combining the positive correlation value image and the negative correlation value image and the positive template image and the negative template image. A polar-coordinates-converted input image and a polar-coordinates-converted template image are employed as the input image and the template image, respectively.

Claims

1. An image verifying apparatus that verifies an image by comparing features of images between an input image of an object to be verified and a template image registered in advance, the image verifying apparatus comprising:

a correlation-value-image separating unit that generates, with a computer, a correlation value image from the input image and the template image, and separates the correlation value image into a positive correlation value image and a negative correlation value image depending on whether a pixel value of the correlation value image is equal to or larger than a threshold;

a template-image separating unit that separates the template image into a positive template image and a negative template image depending on whether a pixel value of the template image is equal to or larger than a threshold;

a positive-negative-separated-correlation-image generating unit that generates a plurality of positive-negative-separated correlation-images having, as a pixel value of the plurality of the positive-negative-separated correlation-images, a value obtained by calculating a product of a pixel value of one of the positive correlation value image and the negative correlation value image and a pixel value of one of the positive template image and the negative template image; and

a verification determining unit that performs a verification determination based on the positive-negative-separated correlation images.

2. The image verifying apparatus according to claim 1, wherein the positive-negative-separated-correlation-image generating unit generates a positive feature area image and a negative feature area image, the positive feature area image taking a value obtained by calculating a product of the positive correlation value image and the positive template image for each pixel as a pixel value, the negative feature area image taking a value obtained by calculating a product of the negative correlation value image and the positive template image for each pixel as a pixel value.

3. The image verifying apparatus according to claim 2, wherein the positive-negative-separated-correlation-image generating unit compares a target pixel in a negative area image generated by using the negative correlation value image with neighboring pixels surrounding a pixel corresponding to the target pixel in a positive area image generated by using the positive correlation value image, and when a pixel value of at least one of the neighboring pixels is larger than a pixel value of the target pixel, performs an expansion process of moving the target pixel to the pixel corresponding to the target pixel.

4. The image verifying apparatus according to claim 1, wherein the positive-negative-separated-correlation-image generating unit generates a positive background area image and a negative background area image, the positive background area image taking a value obtained by calculating a product of the positive correlation value image and the negative template image for each pixel as a pixel value, the negative background area image taking a value obtained by calculating a product of the negative correlation value image and the negative template image for each pixel as a pixel value.

5. The image verifying apparatus according to claim 4, wherein the positive-negative-separated-correlation-image generating unit compares a target pixel in a negative area image generated by using the negative correlation value image with neighboring pixels surrounding a pixel corresponding to the target pixel in a positive area image generated by using the positive correlation value image, and when a pixel value of at least one of the neighboring pixels is larger than a pixel value of the target pixel, performs an expansion process of moving the target pixel to the pixel corresponding to the target pixel.

6. The image verifying apparatus according to claim 1, wherein the positive-negative-separated-correlation-image generating unit generates a positive feature area image, a negative feature area image, a positive background area image, and a negative background area image, the positive feature area image taking a value obtained by calculating a product of the positive correlation value image and the positive template image for each pixel as a pixel value, the negative feature area image taking a value obtained by calculating a product of the negative correlation value image and the positive template image for each pixel as a pixel value, the positive background area image taking a value obtained by calculating a product of the positive correlation value image and the negative template image for each pixel as a pixel value, the negative background area image taking a value obtained by calculating a product of the negative correlation value image and the negative template image for each pixel as a pixel value.

7. The image verifying apparatus according to claim 6, wherein the positive-negative-separated-correlation-image generating unit compares a target pixel in a negative area image generated by using the negative correlation value image with neighboring pixels surrounding a pixel corresponding to the target pixel in a positive area image generated by using the positive correlation value image, and when a pixel value of at least one of the neighboring pixels is larger than a pixel value of the target pixel, performs an expansion process of moving the target pixel to the pixel corresponding to the target pixel.

8. The image verifying apparatus according to claim 1, wherein each of the input image and the template image is an edge image obtained by an image conversion by an edge extracting process employing an edge extraction operator.

9. The image verifying apparatus according to claim 8, wherein the edge image is a normalized edge image obtained by normalizing an edge strength of extracted edge.

10. The image verifying apparatus according to claim 1, wherein the template image is an average image obtained by averaging individual images of the object to be verified.

11. The image verifying apparatus according to claim 1, wherein the correlation value image is an image having, as a pixel value of the correlation value image, a normalized correlation value obtained by normalizing a correlation value between corresponding pixels of the input image and the template image.

12. The image verifying apparatus according to claim 1, wherein the verification determining unit performs the verification determination by calculating a verification value by segmenting the positive-negative-separated correlation images into blocks, calculating a total sum of pixel values in each of the blocks as a block value, and adding a product of the block value and a weighting coefficient for all of the positive-negative-separated correlation-images.

13. The image verifying apparatus according to claim 12, wherein the verification determining unit calculates a value of the weighting coefficient by a linear discriminant analysis.

14. The image verifying apparatus according to claim 1, wherein the object to be verified is a currency.

15. The image verifying apparatus according to claim 1, wherein

the input image is that of a circular object,

the image verifying apparatus further comprises a polar-coordinates-converted-image generating unit that performs a polar-coordinates conversion of the input image and the template image, and generates a ρ

-θ

input image and a ρ

-θ

template image for which a deviation of rotation between the input image and the template image has been compensated;

the correlation-value-image separating unit generates the correlation value image from the ρ

-θ

input image and the ρ

-θ

template image, and

the template-image separating unit uses the ρ

-θ

template image for separation.

16. The image verifying apparatus according to claim 15, wherein the positive-negative-separated-correlation-image generating unit generates a positive feature area image and a negative feature area image, the positive feature area image taking a value obtained by calculating a product of the positive correlation value image and the positive template image for each pixel as a pixel value, the negative feature area image taking a value obtained by calculating a product of the negative correlation value image and the positive template image for each pixel as a pixel value.

17. The image verifying apparatus according to claim 16, wherein the positive-negative-separated-correlation-image generating unit compares a target pixel in a negative area image generated by using the negative correlation value image with neighboring pixels surrounding a pixel corresponding to the target pixel in a positive area image generated by using the positive correlation value image, and when a pixel value of at least one of the neighboring pixels is larger than a pixel value of the target pixel, performs an expansion process of moving the target pixel to the pixel corresponding to the target pixel.

18. The image verifying apparatus according to claim 15, wherein the positive-negative-separated-correlation-image generating unit generates a positive background area image and a negative background area image, the positive background area image taking a value obtained by calculating a product of the positive correlation value image and the negative template image for each pixel as a pixel value, the negative background area image taking a value obtained by calculating a product of the negative correlation value image and the negative template image for each pixel as a pixel value.

19. The image verifying apparatus according to claim 18, wherein the positive-negative-separated-correlation-image generating unit compares a target pixel in a negative area image generated by using the negative correlation value image with neighboring pixels surrounding a pixel corresponding to the target pixel in a positive area image generated by using the positive correlation value image, and when a pixel value of at least one of the neighboring pixels is larger than a pixel value of the target pixel, performs an expansion process of moving the target pixel to the pixel corresponding to the target pixel.

20. The image verifying apparatus according to claim 15, wherein the positive-negative-separated-correlation-image generating unit generates a positive feature area image, a negative feature area image, a positive background area image, and a negative background area image, the positive feature area image taking a value obtained by calculating a product of the positive correlation value image and the positive template image for each pixel as a pixel value, the negative feature area image taking a value obtained by calculating a product of the negative correlation value image and the positive template image for each pixel as a pixel value, the positive background area image taking a value obtained by calculating a product of the positive correlation value image and the negative template image for each pixel as a pixel value, the negative background area image taking a value obtained by calculating a product of the negative correlation value image and the negative template image for each pixel as a pixel value.

21. The image verifying apparatus according to claim 20, wherein the positive-negative-separated-correlation-image generating unit compares a target pixel in a negative area image generated by using the negative correlation value image with neighboring pixels surrounding a pixel corresponding to the target pixel in a positive area image generated by using the positive correlation value image, and when a pixel value of at least one of the neighboring pixels is larger than a pixel value of the target pixel, performs an expansion process of moving the target pixel to the pixel corresponding to the target pixel.

22. The image verifying apparatus according to claim 15, wherein each of the ρ

-θ

input image and the ρ

-θ

template image is an edge image obtained by an image conversion by an edge extracting process employing an edge extraction operator.

23. The image verifying apparatus according to claim 22, wherein the edge image is a normalized edge image obtained by normalizing an edge strength of extracted edge.

24. The image verifying apparatus according to claim 15, wherein the template image is an average image obtained by averaging individual images of the object to be verified.

25. The image verifying apparatus according to claim 15, wherein the correlation value image is an image having, as a pixel value of the correlation value image, a normalized correlation value obtained by normalizing a correlation value between corresponding pixels of the ρ

-θ

input image and the ρ

-θ

template image.

26. The image verifying apparatus according to claim 15, wherein the verification determining unit performs the verification determination by calculating a verification value by segmenting the positive-negative-separated correlation images into blocks, calculating a total sum of pixel values in each of the blocks as a block value, and adding a product of the block value and a weighting coefficient for all of the positive-negative-separated correlation-images.

27. The image verifying apparatus according to claim 26, wherein the verification determining unit calculates a value of the weighting coefficient by a linear discriminant analysis.

28. The image verifying apparatus according to claim 15, wherein the polar-coordinates-converted-image generating unit compensates the deviation of rotation between the input image and the template image by performing a parallel shift of either one of the ρ

-θ

input image and the ρ

-θ

template image.

29. The image verifying apparatus according to claim 15, wherein the circular object is a coin.

30. An image verifying method of verifying an image by comparing features of images between an input image of an object to be verified and a template image registered in advance, the image verifying method comprising:

correlation-value-image separating by a correlation-value-image separating unit including

generating, with a computer, a correlation value image from the input image and the template image; and

separating the correlation value image into a positive correlation value image and a negative correlation value image depending on whether a pixel value of the correlation value image is equal to or larger than a threshold;

template-image separating by a template-image separating unit including

separating the template image into a positive template image and a negative template image depending on whether a pixel value of the template image is equal to or larger than a threshold;

positive-negative-separated-correlation-image generating by a positive-negative-separated-correlation-image generating unit including

generating a plurality of positive-negative-separated correlation-images having, as a pixel value of the plurality of the positive-negative-separated correlation-images, a value obtained by calculating a product of a pixel value of one of the positive correlation value image and the negative correlation value image and a pixel value of one of the positive template image and the negative template image; and

verification determining by a verification determining unit including

performing a verification determination based on the positive-negative-separated correlation-images.

31. The image verifying method according to claim 30, wherein

the input image is that of a circular object,

the image verifying method further comprises polar-coordinates-converted-image generating by a polar-coordinates-converted-image generating unit including

performing a polar-coordinates conversion of the input image and the template image;

and

generating a ρ

-θ

input image and a ρ

-θ

template image for which a deviation of rotation between the input image and the template image has been compensated,

the correlation-value-image separating includes generating the correlation value image from the ρ

-θ

input image and the ρ

-θ

template image, and

the template-image separating includes using the ρ

-θ

template image for separation.

32. A non-transitory computer readable storage medium having stored therein an image verifying program for verifying an image by comparing features of images between an input image of an object to be verified and a template image registered in advance, the image verifying program causing a computer to execute the image verifying method according to claim 30.

33. A non-transitory computer readable storage medium having stored therein an image verifying program for verifying an image by comparing features of images between an input image of a circular object and a template image registered in advance, the image verifying program causing a computer to execute the image verifying method according to claim 31.