Identifying and redressing shadows in connection with digital watermarking and fingerprinting

• US 8,488,900 B2
• Filed: 06/21/2011
• Issued: 07/16/2013
• Est. Priority Date: 06/23/2010
• Status: Expired due to Fees

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Conwell, William Y.
• Primary Examiner(s): MARIAM, DANIEL G
• Application Number:
  US13/165,604
• Publication Number:
  US 20110317875A1
• Time in Patent Office: 756 Days
• Field of Search: 382/174, 382/199, 382/269, 382/275, 382/307, 382/100, 382/264
• US Class Current: 382/269
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement
• CPC Class Codes: G06T 7/507 from shading G06T7/586 takes precedence

Abstract

The present disclosure relates generally to cell phones and cameras, and to shadow detection in images captured by such cell phones and cameras. One claim recites a method comprising: identifying a shadow cast by a camera on a subject being imaged; and using a programmed electronic processor, redressing the shadow in connection with: i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject. Another claim recites a method comprising: identifying a shadow cast by a cell phone on a subject being imaged by a camera included in the cell phone; and using a programmed electronic processor, determining a proximity of the camera to the subject based on an analysis of the shadow. Of course, other claims and combinations are provided too.

Claims

1. A method comprising:

identifying a shadow cast by a smartphone or camera on a subject being imaged; and

using a programmed electronic processor, redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject, in which said redressing the shadow comprises disregarding image content associated with the shadow when reading the digital watermark or calculating a fingerprint.

2. The method of claim 1 in which a cell phone comprises the camera.

3. The method of claim 1 in which the subject comprises a printed or displayed object or graphic.

4. The method of claim 1 in which said act of identifying a shadow analyzes an apparent position of the subject relative to a suspected shadow over two or more image frames.

5. The method of claim 1 further comprising reading a digital watermark from imagery representing the subject after said act of redressing the shadow.

6. A non-transitory computer readable medium comprising instructions stored thereon to cause an electronic process to perform the method of claim 1.

7. The method of claim 1 further comprising calculating a fingerprint from the imagery representing the subject after said act of redressing the shadow.

8. The method of claim 1 in which the imagery comprises video.

9. A method comprising:

identifying a shadow cast by a smartphone or camera on a subject being imaged, in which said identifying locates candidate edges, and in which candidate edges once identified in image data are matched against a series of reference templates, in which candidate edges once identified in image data are matched against a series of reference templates; and

using a programmed electronic processor, redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject.

10. The method of claim 9 in which the reference templates correspond to shadows produced by different edges of the smartphone or camera, or a smart phone including the camera.

11. A method comprising:

identifying a shadow cast by a smartphone or camera on a subject being imaged, in which said act of identifying a shadow compares an image frame captured without a strobe flash with an image frame captured with a strobe flash to identify the shadow; and

using a programmed electronic processor, redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject.

12. A method comprising:

identifying a shadow cast by a smartphone or camera on a subject being imaged; and

using a programmed electronic processor, redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject, in which said act of redressing the shadow comprises ranking candidate pixel or image regions for submission to a watermark detector or to a fingerprint analyzer, and in which shadowed regions are ranked relatively lower than un-shadowed regions.

13. A method comprising:

identifying a shadow cast by a smartphone or camera on a subject being imaged; and

using a programmed electronic processor, redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject, in which said act of redressing the shadow comprises discerning information about two lighting sources.

14. A cell phone comprising:

a camera for capturing imagery;

memory for buffering captured imagery; and

an electronic processor programmed for;

identifying a shadow cast by the cell phone on a subject being imaged by said camera; and

redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject, in which said redressing the shadow comprises disregarding image content associated with the shadow when reading the digital watermark or calculating a fingerprint.

15. The cell phone of claim 14 in which the subject comprises a printed or displayed object or graphic.

16. A cell phone comprising:

a camera for capturing imagery;

memory for buffering captured imagery; and

an electronic processor programmed for;

identifying a shadow cast by the cell phone on a subject being imaged by said camera, in which said identifying locates candidate edges, in which candidate edges once identified in image data are matched against a series of reference templates; and

redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject.

17. The cell phone of claim 16 in which the reference templates correspond to shadows produced by different edges of the camera, or a smart phone including the camera.

18. A cell phone comprising:

a camera for capturing imagery;

memory for buffering captured imagery; and

an electronic processor programmed for;

identifying a shadow cast by the cell phone on a subject being imaged by said camera, in which said identifying a shadow compares an image frame captured without a strobe flash with an image frame captured with a strobe flash to identify the shadow; and

redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject.

19. A cell phone comprising:

a camera for capturing imagery;

memory for buffering captured imagery; and

an electronic processor programmed for;

identifying a shadow cast by the cell phone on a subject being imaged by said camera, in which said identifying a shadow analyzes an apparent position of the subject relative to a suspected shadow over two or more image frames; and

redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject.

20. A cell phone comprising:

a camera for capturing imagery;

memory for buffering captured imagery; and

an electronic processor programmed for;

identifying a shadow cast by the cell phone on a subject being imaged by said camera; and

redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject, in which said redressing the shadow comprises ranking candidate pixel or image regions for submission to a watermark detector or to a fingerprint analyzer, and in which shadowed regions are ranked relatively lower than un-shadowed regions.

21. A cell phone comprising:

a camera for capturing imagery;

memory for buffering captured imagery; and

an electronic processor programmed for;

identifying a shadow cast by the cell phone on a subject being imaged by said camera; and

redressing the shadow in connection with;

i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject, in which said redressing the shadow comprises discerning information about two lighting sources.