Systems and methods for a gradient-based metric for spoof detection

• US 10,176,362 B1
• Filed: 12/30/2016
• Issued: 01/08/2019
• Est. Priority Date: 11/10/2016
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Krishnapura, Rohini
• Primary Examiner(s): Roz, Mark
• Application Number:
  US15/395,634
• Time in Patent Office: 739 Days
• Field of Search: None
• CPC Class Codes: G06V 10/50 by performing operations within image blocks; by using histograms, e.g. histogram of oriented gradients [HoG]; by summing image-intensity values; Projection analysis
• CPC Class Codes: G06V 10/54 relating to texture
• CPC Class Codes: G06V 20/695 Preprocessing, e.g. image segmentation
• CPC Class Codes: G06V 40/1365 Matching; Classification

Abstract

A system and method for performing spoof detection are disclosed. The method includes: receiving an input image of a biometric; computing a gradient image of the biometric based on the input image of the biometric; dividing the gradient image into blocks of pixels; computing, for each block, a variance value corresponding to a variance of the pixels in the block; and, determining whether the input image is a replica of the biometric based on the variance values of the blocks of the gradient image.

Claims

1. A method for spoof detection, comprising:

receiving an input image of a biometric;

computing a gradient image of the biometric based on the input image of the biometric, wherein each pixel of the gradient image represents a value for a directional change in a characteristic at a corresponding pixel location in the input image;

dividing the gradient image into blocks of pixels;

computing, for each block of pixels, a set of gradient values, wherein each gradient value in the set of gradient values for a given block corresponds to a gradient value of a different pixel of the gradient image in the given block;

computing, for each block of pixels, a variance value, wherein the variance value for a given block corresponds to a variance of the gradient values in the set of gradient values for the given block; and

determining whether the input image is a replica of the biometric based on the variance values of the blocks of pixels of the gradient image.

2. The method of claim 1, wherein each block corresponds to a non-overlapping set of pixels of the gradient image.

3. The method of claim 1, wherein the input image comprises a grayscale image of a fingerprint, and computing the gradient image comprises computing a first order derivative of fingerprint ridges included in the grayscale image of the fingerprint.

4. The method of claim 1, wherein the blocks comprise square-shaped blocks of pixels.

5. The method of claim 1, wherein after computing, for each block of pixels, the set of gradient values, the method further comprises:

computing, for each block of pixels, a histogram of the gradient values in the set of gradient values of the pixels in the block.

6. The method of claim 5, further comprising:

plotting the variance values as a histogram of variance.

7. The method of claim 1, wherein a user is denied access to a device based on determining that the input image is a replica of the biometric.

8. The method of claim 1, wherein the gradient image is divided into a fixed number of blocks regardless of dimensions of the input image.

9. The method of claim 1, wherein the biometric comprises a fingerprint of a finger, and the replica comprises a gelatin mold, a graphite mold, or a wood glue mold of the fingerprint of the finger.

10. The method of claim 1, wherein the biometric comprises a fingerprint of a finger, and computing the gradient image comprises computing a first order derivative of fingerprint ridges included in the fingerprint of the finger.

20. The method of claim 1, wherein the characteristic comprises intensity or color at the corresponding pixel location in the input image.

11. A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, causes a computing device to perform spoof detection, by performing steps comprising:

receiving an input image of a biometric;

computing a gradient image of the biometric based on the input image of the biometric, wherein each pixel of the gradient image represents a value for a directional change in a characteristic at a corresponding pixel location in the input image;

dividing the gradient image into blocks of pixels;

computing, for each block of pixels, a set of gradient values, wherein each gradient value in the set of gradient values for a given block corresponds to a gradient value of a different pixel of the gradient image in the given block;

computing, for each block of pixels, a variance value, wherein the variance value for a given block corresponds to a variance of the gradient values in the set of gradient values for the given block; and

determining whether the input image is a replica of the biometric based on the variance values of the blocks of pixels of the gradient image.

12. The computer-readable storage medium of claim 11, wherein each block corresponds to a non-overlapping set of pixels of the gradient image.

13. The computer-readable storage medium of claim 11, wherein the input image comprises a grayscale image of a fingerprint, and computing the gradient image comprises computing a first order derivative of fingerprint ridges included in the grayscale image of the fingerprint.

14. The computer-readable storage medium of claim 11, wherein after computing, for each block of pixels, the set of gradient values, the steps further comprise:

computing, for each block of pixels, a histogram of the gradient values in the set of gradient values of the pixels in the block.

15. The computer-readable storage medium of claim 11, wherein a user is denied access to a device based on determining that the input image is a replica of the biometric.

16. The computer-readable storage medium of claim 11, wherein the gradient image is divided into a fixed number of blocks regardless of dimensions of the input image.

17. The computer-readable storage medium of claim 11, wherein the biometric comprises a fingerprint of a finger, and the replica comprises a gelatin mold, a graphite mold, or a wood glue mold of the fingerprint of the finger.

18. The computer-readable storage medium of claim 11, wherein the biometric comprises a fingerprint of a finger, and computing the gradient image comprises computing a first order derivative of fingerprint ridges included in the fingerprint of the finger.

19. A device, comprising:

a biometric sensor; and

a processor configured to;

receive, from the biometric sensor, an input image of a biometric;

compute a gradient image of the biometric based on the input image of the biometric, wherein each pixel of the gradient image represents a value for a directional change in a characteristic at a corresponding pixel location in the input image;

divide the gradient image into blocks of pixels;

compute, for each block of pixels, a set of gradient values, wherein each gradient value in the set of gradient values for a given block corresponds to a gradient value of a different pixel of the gradient image in the given block;

compute, for each block of pixels, a variance value, wherein the variance value for a given block corresponds to a variance of the gradient values in the set of gradient values for the given block; and

determine whether the input image is a replica of the biometric based on the variance values of the blocks of pixels of the gradient image.