Real-Time Face Tracking in a Digital Image Acquisition Device

• US 20090263022A1
• Filed: 06/18/2007
• Published: 10/22/2009
• Est. Priority Date: 08/11/2006
• Status: Active Grant

• Current Assignee: FotoNation Limited (Adeia Inc.)
• Original Assignee: FotoNation Vision Limited (Adeia Inc.)
• Inventors: Steinberg, Eran, Petrescu, Stefan, Drimbarean, Alexandru, Bigioi, Petronel, Corcoran, Peter
• Granted Patent: US 8,055,029 B2
• Time in Patent Office: Days
• US Class Current: 382/195
• CPC Class Codes: G06F 18/2148 characterised by the process organisation or structure, e.g. boosting cascade
• CPC Class Codes: G06V 30/19147 Obtaining sets of training patterns; Bootstrap methods, e.g. bagging or boosting
• CPC Class Codes: G06V 30/2504 Coarse or fine approaches, e.g. resolution of ambiguities or multiscale approaches
• CPC Class Codes: G06V 40/162 using pixel segmentation or colour matching
• CPC Class Codes: G06V 40/165 using facial parts and geometric relationships
• CPC Class Codes: G06V 40/167 using comparisons between temporally consecutive images
• CPC Class Codes: G06V 40/171 Local features and components; Facial parts eye characteristics G06V40/18; Occluding parts, e.g. glasses; Geometrical relationships
• CPC Class Codes: H04N 1/2112 using still video cameras
• CPC Class Codes: H04N 1/32112 in a separate computer file, document page or paper sheet, e.g. a fax cover sheet H04N1/32122 takes precedence
• CPC Class Codes: H04N 1/32128 attached to the image data, e.g. file header, transmitted message header, information on the same page or in the same computer file as the image for information embedded in the image H04N1/32144
• CPC Class Codes: H04N 2101/00 Still video cameras
• CPC Class Codes: H04N 2201/0084 Digital still camera
• CPC Class Codes: H04N 2201/3205 of identification information, e.g. name or ID code H04N2201/3209 takes precedence
• CPC Class Codes: H04N 23/61 based on recognised objects
• CPC Class Codes: H04N 23/611 where the recognised objects include parts of the human body
• CPC Class Codes: H04N 23/635 Region indicators; Field of view indicators
• CPC Class Codes: H04N 23/695 Control of camera direction for changing a field of view, e.g. pan, tilt or based on tracking of objects

Abstract

An image processing apparatus for tracking faces in an image stream iteratively receives an acquired image from the image stream including one or more face regions. The acquired image is sub-sampled at a specified resolution to provide a sub-sampled image. An integral image is then calculated for a least a portion of the sub-sampled image. Fixed size face detection is applied to at least a portion of the integral image to provide a set of candidate face regions. Responsive to the set of candidate face regions produced and any previously detected candidate face regions, the resolution is adjusted for sub-sampling a subsequent acquired image.

Claims

1. A method of detecting faces in an image stream using a digital image acquisition device comprising:

a. receiving an acquired image from said image stream including one or more face regions;

b. sub-sampling said acquired image at a specified resolution to provide a sub-sampled image;

c. identifying one or more regions of said acquired image predominantly including skin tones;

d. calculating a corresponding integral image for at least one of said skin tone regions of said sub-sampled acquired image;

e. applying face detection to at least a portion of said integral image to provide a set of one or more candidate face regions each having a given size and a respective location; and

f for a candidate face region associated with a previous image in said stream, enhancing the contrast of the luminance characteristics of the corresponding region of said acquired image.

2. The method of claim 1, further comprising repeating a. to f.

3. A method as claimed in claim 1, wherein said identifying is performed on said sub-sampled image.

4. A method as claimed in claim 1, wherein said face detection is performed with relaxed face detection parameters.

5. A method as claimed in claim 1, wherein said enhancing is performed on said sub-sampled image.

6. A method as claimed in claim 1, wherein said enhancing is performed during calculation of said integral image.

7. A method as claimed in claim 1, in a face detection mode of said digital image acquisition device, each new acquired image is acquired with progressively increased exposure parameters until at least one candidate face region is detected.

8. A method as claimed in claim 1, further comprising:

providing a quality measure for one of a candidate region of an image or said acquired image; and

wherein said enhancing is responsive to said quality measure.

9. A method as claimed in claim 8 wherein said quality measure is based on one or more of a luminance of said candidate region or said acquired image;

or a variance of said luminance of said candidate region or said acquired image.

10. A method as claimed in claim 9 wherein said enhancing is responsive to a maximum value of said luminance being below a threshold value to increase low values of luminance of said candidate region or said acquired image.

11. A method as claimed in claim 9 wherein said enhancing is responsive to a minimum value of said luminance being above a threshold value to decrease high values of luminance of said candidate region or said acquired image.

12. A method as claimed in claim 9 wherein said enhancing is responsive to a value of said variance of said luminance being above a threshold value to stop enhancing said candidate region or said acquired image.

13. A method as claimed in claim 9 wherein said identifying one or more regions of said acquired image predominantly including skin tones comprises applying one of a number of filters to define said one or more regions of said acquired image predominantly including skin tones, at least one of said filters including a restrictive skin filter and at least one of said filters including a relaxed skin filter.

14. A method as claimed in claim 13 comprising:

applying said relaxed skin filter in response to said quality measure indicating that the quality of said one of a candidate region of an image or said acquired image is poor.

15. An image processing apparatus including one or more processors and one or more digital storage media having digitally-encoded instructions embedded therein for programming the one or more processors to perform an iterative method of detecting faces in an image stream, the method comprising:

a. receiving an acquired image from an image stream including one or more face regions;

b. sub-sampling said acquired image at a specified resolution to provide a sub-sampled image;

c. identifying one or more regions of said acquired image predominantly including skin tones;

d. calculating a corresponding integral image for at least one of said skin tone regions of said sub-sampled image;

e. applying face detection to at least a portion of said integral image to provide a set of candidate face regions each having a given size and a respective location; and

f. for a candidate face region associated with a previous image in said stream, enhancing the contrast of the luminance characteristics of the corresponding region of said acquired image.

16. A method of detecting faces in an image stream using a digital image acquisition device comprising:

a. receiving an acquired image from said image stream including one or more face regions;

b. sub-sampling said acquired image at a specified resolution to provide a sub-sampled image;

c. identifying one or more regions of said acquired image predominantly including skin tones;

d. calculating a corresponding integral image for at least one of said skin tone regions of said sub-sampled acquired image;

e. applying face detection to at least a portion of said integral image to provide a set of one or more candidate face regions each having a given size and a respective location; and

f. responsive to failing to detect at least one face region for said image, enhancing the contrast of the luminance characteristics for at least a region corresponding to one of said skin tone regions in a subsequently acquired image.

17. A method as claimed in claim 16 wherein said identifying one or more regions of said acquired image predominantly including skin tones comprises applying one of a number of filters to define said one or more regions of said acquired image predominantly including skin tones, at least one of said filters including a restrictive skin filter and at least one of said filters including a relaxed skin filter.

18. A method as claimed in claim 17 further comprising:

responsive to failing to detect at least one face region for said image, applying said relaxed skin filter to a subsequently acquired image.

19. A method as claimed in claim 18 further comprising:

responsive to failing to detect at least one face region for six successively acquired images, applying said relaxed skin filter to three subsequently acquired images.

20. A method as claimed in claim 19 further comprising:

responsive to failing to detect at least one face region for fifteen successively acquired images, applying a further relaxed skin filter to three subsequently acquired images.

21. A method as claimed in claim 17 further comprising:

responsive to failing to detect at least one face region for six successively acquired images, enhancing the contrast of the luminance characteristics for at least a region corresponding to one of said skin tone regions in three subsequently acquired images.

22. A method as claimed in claim 17 wherein said enhancing comprises adjusting a luminance value i less than or equal to a threshold T according to the formula T*pow(i/T, r) and adjusting a luminance value I greater than said threshold T according to the formula (L−

1−

(L−

1−

T)*pow((L−

1−

i)/(L−

1−

T),r)) where T=100, r=0.4 and L is the maximum value for luminance.

23. An image processing apparatus including one or more processors and one or more digital storage media having digitally-encoded instructions embedded therein for programming the one or more processors to perform an iterative method of detecting faces in an image stream, the method comprising:

a. receiving an acquired image from said image stream including one or more face regions;

b. sub-sampling said acquired image at a specified resolution to provide a sub-sampled image;

c. identifying one or more regions of said acquired image predominantly including skin tones;

d. calculating a corresponding integral image for at least one of said skin tone regions of said sub-sampled acquired image;

e. applying face detection to at least a portion of said integral image to provide a set of one or more candidate face regions each having a given size and a respective location; and

f. responsive to failing to detect at least one face region for said image, enhancing the contrast of the luminance characteristics for at least a region corresponding to one of said skin tone regions in a subsequently acquired image.

24. An image processing apparatus including one or more processors and one or more digital storage media having digitally-encoded instructions embedded therein for programming the one or more processors to perform an iterative method of detecting faces in an image stream, the method comprising:

a. receiving an acquired image from said image stream including one or more face regions;

b. sub-sampling said acquired image at a specified resolution to provide a sub-sampled image;

c. identifying one or more regions of said acquired image predominantly including skin tones by applying one of a number of filters to define said one or more regions of said acquired image predominantly including skin tones, at least one of said filters including a restrictive skin filter and at least one of said filters including a relaxed skin filter;

d. calculating a corresponding integral image for at least one of said skin tone regions of said sub-sampled acquired image;

e. applying face detection to at least a portion of said integral image to provide a set of one or more candidate face regions each having a given size and a respective location;

f. providing a quality measure for one of a candidate region of an image or said acquired image; and

g. responsive to said quality measure, applying said relaxed skin filter to a subsequently acquired image.

25. The apparatus of claim 24, wherein responsive to failing to detect at least one face region for said image, the method further comprises enhancing the contrast of the luminance characteristics for at least a region corresponding to one of said skin tone regions in a subsequently acquired image.