Real-time face tracking in a digital image acquisition device

A method of tracking faces in an image stream with a digital image acquisition device, 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. calculating a corresponding integral image for a least a portion of said sub-sampled image;
• d. applying a fixed size 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;
• e. responsive at least in part to the given size and respective location of said candidate face regions, adjusting a resolution for sub-sampling a next acquired image;
• and
• f. repeating steps a. to e. at the adjusted resolution,
• wherein said adjusting comprises cycling through a set of at least approximately four sub-sampling resolutions.

A method of tracking faces in an image stream with a digital image acquisition device, 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. calculating a corresponding integral image for a least a portion of said sub-sampled image;
• d. applying a fixed size 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;
• e. responsive at least in part to the given size and respective location of said candidate face regions, adjusting a resolution for sub-sampling a next acquired image;
• and
• f. repeating steps a. to e. at the adjusted resolution,
• wherein said adjusting is responsive to said image being acquired at approximately infinite focus for adjusting said sub-sampling resolution to maximum resolution.

A method of tracking faces in an image stream with a digital image acquisition device, 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. calculating a corresponding integral image for a least a portion of said sub-sampled image;
• d. applying a fixed size 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;
• e. responsive at least in part to the given size and respective location of said candidate face regions, adjusting a resolution for sub-sampling a next acquired image;
• and
• f. repeating steps a. to e. at the adjusted resolution,
• wherein a. to e. are performed periodically on a selected plurality of images of an image stream, said plurality of images including a main acquired image chronologically following a plurality of images of said selected plurality of images.

A method of tracking faces in an image stream with a digital image acquisition device, 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. calculating a corresponding integral image for a least a portion of said sub-sampled image;
• d. applying a fixed size 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;
• e. responsive at least in part to the given size and respective location of said candidate face regions adjusting a resolution for sub-sampling a next acquired image;
• and
• f. repeating steps a. to e. at the adjusted resolution, and
• g. further comprising responsive to said acquired image being captured with a flash, analyzing regions of said acquired image corresponding to said tracked candidate face regions for red-eye defects.

An image processing apparatus for tracking faces in an image stream comprising 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 tracking 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 the acquired image at a specified resolution to provide a sub-sampled image;
• c. calculating a corresponding integral image for a least a portion of said sub-sampled image;
• d. applying a fixed size face detection to at least a portion of said integral image to provide a set of one or more candidate face regions;
• and
• e. responsive at least in part to said set of candidate face regions, adjusting a resolution for sub-sampling a next acquired image, and
• further comprising, for each region of said acquired image corresponding to a region of said merged set of candidate face regions;
• f. calculating an integral image;
• and
• g. applying variable-sized face detection to each merged region integral image to provide a set of confirmed face regions and a set of rejected face regions.

A method of recognizing faces in an image stream with a digital image acquisition device, comprising:

• a. providing a database comprising an identifier and associated parameters for each of a number of faces to be recognized;
• b. receiving an acquired image from an image stream including one or more face regions;
• c. sub-sampling said acquired image at a specified resolution to provide a sub-sampled image;
• d. calculating a corresponding integral image for at least a portion of said sub-sampled 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. using a database, selectively applying face recognition to at least one of the candidate face regions;
• g. providing an identifier for each face recognized in the at least one candidate face region;
• and
• h. storing the identifier for each recognized face in association with at least one image of said image stream, and
• i. further comprising providing a level of confidence for each candidate face region based on the face detection, and applying recognition only to candidate face regions having a confidence level higher than a predetermined threshold.

An image processing apparatus including one or more processors, a database including an identifier and associated parameters for each of a number of faces to be recognized, 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 recognizing 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 first-sub-sampled image;
• c. calculating a corresponding integral image for a least a portion of said sub-sampled image;
• d. applying face detection to at least a portion of said integral image to provide a set of one or more candidate face regions each including a given size and a respective location;
• e. selectively applying face recognition using said database to at least one of the candidate face regions to provide an identifier for a face recognized in a candidate face region;
• and
• f. storing the identifier for the recognized face in association with at least one image of said image stream, and
• g. further comprising providing a level of confidence for each candidate face region based on the face detection and applying recognition only to candidate face regions having a confidence level higher than a predetermined threshold.

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 a least one of said skin tone regions of said sub-sampled acquired image;
• and
• 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
• wherein 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.

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 a least one of said skin tone regions of said sub-sampled image;
• and
• 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
• wherein 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.