Method of identifying symbolic points on an image of a person's face

• US 8,144,946 B2
• Filed: 12/05/2007
• Issued: 03/27/2012
• Est. Priority Date: 01/30/2007
• Status: Active Grant

• Current Assignee: Continental Automotive France (Continental AG)
• Original Assignee: Continental Automotive France (Continental AG)
• Inventors: Godreau, Bertrand
• Primary Examiner(s): Le, Brian
• Application Number:
  US12/524,765
• Publication Number:
  US 20100061639A1
• Time in Patent Office: 1,574 Days
• Field of Search: 382/115, 382/117, 382/118, 382/162, 382/165, 382/167, 382/274, 348/78, 351/209, 351/210, 351/211, 351/212, 396/18, 396/51, 396/158
• US Class Current: 382/118
• CPC Class Codes: G06V 40/171 Local features and components; Facial parts eye characteristics G06V40/18; Occluding parts, e.g. glasses; Geometrical relationships

Abstract

A method for identifying symbolic points on the image of a face including images of a right eye, left eye and mouth, includes:

• • detecting and identifying elements with strong contrasts such as the irises, nostrils, or mouth;
  • selecting zones of the image with respect to the elements with strong contrasts including a priori two sought-after symbolic points interrelated by a morphological criterion;
  • searching within the zones for natural points through the convergence of lines of the image and, for each natural point, determining a signature, determining a score with respect to pre-established signatures and selecting the natural points having a score above a threshold value;
  • in each zone, identifying pairs of natural points and determining for each identified pair a score with respect to pairs of standard symbolic points and selecting the pair of natural points having the best score as symbolic points of the zone.

Claims

1. A method (10) for identifying symbolic points on the image of a face (1), said image comprising a priori the images of a right eye, of a left eye and of a mouth, said method successively comprising the steps of:

a) detecting (11) elements (2a, 2b, 3a, 3b, 4) with strong contrasts of the face and identifying said elements with strong contrasts;

b) selecting (12) at least one zone (20a, 20b, 40) of the image, said at least one zone having a position and dimensions on the image (1) that are determined with respect to the elements with strong contrasts (2a, 2b, 3a, 3b, 4) and such that it contains a priori two sought-after symbolic points interrelated by a morphological criterion;

c) searching (13) for points defined by the convergence of separation lines of contrasted zones of the image, termed natural points, in said at least one zone;

d) determining (14) a signature for each of said natural points by calculating the gradient of the image contrast around the natural point;

e) determining (15a) for each natural point at least one score characterizing a resemblance of the signature of the point with respect to pre-established signatures of symbolic points and selecting (15b) the natural points having a score above a threshold value;

f) from among the natural points of the at least one zone whose scores are above a threshold value, identifying (16) pairs of natural points, each pair being determined by a first natural point and by a second natural point whose relative position in the zone considered with respect to the first natural point corresponds to a position close to pre-established relative positions of pairs of standard symbolic points searched for in said at least one zone and determining for each identified pair a score characteristic of the deviation of the pair considered with respect to the pairs of standard symbolic points;

g) in the at least one zone, selecting (17) the pair of natural points having the best score as symbolic points of said at least one zone considered of the image of the face (1).

2. The method as claimed in claim 1 in which the elements with strong contrasts (2a, 2b, 3a, 3b, 4) of the face are chosen from among irises of the eyes, nostrils and the mouth.

3. The method as claimed in claim 1 in which the selection (12) of the zones (20a, 20b, 40) of the image is determined so as to correspond to a zone overlapping the right eye and/or to a zone overlapping the left eye and/or to a zone overlapping the mouth.

4. The method as claimed in claim 3 in which the pair of symbolic points in a zone overlapping an eye is searched for (16) by the identification of the convergence of natural lines consisting of an edge of an upper eyelid and of an edge of a lower eyelid of the eye.

5. The method as claimed in claim 3 in which the pair of symbolic points in a zone overlapping the mouth is searched for (16) by the identification of the convergence of natural lines consisting of an edge of an upper lip and of an edge of a lower lip of the mouth.

6. The method as claimed in claim 1 in which the zones (20a, 20b, 40) are selected in such a way that, in each zone, the pre-established relative positions of pairs of standard symbolic points (9) correspond to a symmetric arrangement of the standard symbolic points with respect to a reference line of the zone considered.

7. The method as claimed in claim 1 in which the image of the face (1) is obtained from a digital image with low resolution, preferably fewer than 500 lines of 500 image points.

8. The method as claimed in claim 7 in which the digital image is produced in the near infrared.

9. The method as claimed in claim 2 in which the selection (12) of the zones (20a, 20b, 40) of the image is determined so as to correspond to a zone overlapping the right eye and/or to a zone overlapping the left eye and/or to a zone overlapping the mouth.

10. The method as claimed in claim 9 in which the pair of symbolic points in a zone overlapping an eye is searched for (16) by the identification of the convergence of natural lines consisting of an edge of an upper eyelid and of an edge of a lower eyelid of the eye.

11. The method as claimed in claim 4 in which the pair of symbolic points in a zone overlapping the mouth is searched for (16) by the identification of the convergence of natural lines consisting of an edge of an upper lip and of an edge of a lower lip of the mouth.

12. The method as claimed in claim 10 in which the pair of symbolic points in a zone overlapping the mouth is searched for (16) by the identification of the convergence of natural lines consisting of an edge of an upper lip and of an edge of a lower lip of the mouth.