Patent ID: 7315631

Claim:
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 merging said set of candidate face regions with any previously detected face regions to provide a set of candidate face regions of potentially different sizes, and h. further comprising, for each region of said acquired image corresponding to a region of said merged set of candidate face regions: calculating an integral image; and 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.