System and method for face detection using candidate image region selection
DCFirst Claim
1. A method of pre-filtering an input image to determine whether said input image includes a target image pattern of interest comprising steps of:
- receiving said input image;
correlating said input image with preselected reference data to derive a correlation image, said preselected reference data being representative of said target image pattern of interest, said correlation image having image data indicative of correlations between said input image and said preselected reference data; and
selecting a candidate region of said input image having a likelihood of containing said target image pattern of interest on a basis of correlating said input image with said preselected reference data, said step of selecting including identifying potential candidate regions of said input image based on detecting a local maximum in said correlation image and screening said potential candidate regions by analyzing a grayscale characteristic of said potential candidate regions, said screening including discarding said potential candidate regions that do not satisfy a predetermined criterion with respect to said grayscale characteristic in order to increase a probability that said selected candidate region contains said target image pattern of interest.
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Litigations
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Accused Products
Abstract
A face detection system and a method of pre-filtering an input image for face detection utilize a candidate selector that selects candidate regions of the input image that potentially contains a picture of a human face. The candidate selector operates in conjunction with an associated face detector that verifies whether the candidate regions contain a human face. In the preferred embodiment, the candidate selector includes a linear matched filter and a non-linear filter that operate in series to select the candidate regions from the input image. Initially, the linear matched filter performs a linear correlation on the input image using a filtering kernel to derive a correlation image. The linear matched filter selects regions of the input image that have a local maximum in the correlation image and have correlation values greater than a threshold correlation value. Preferably, the linear correlation is performed in the discrete cosine transform (DCT) domain. The non-linear filter then examines contrast values from various sub-regions of the image regions that were selected by the linear matched filter to screen for suitable candidate regions. The filtering kernel used by the linear matched filter is calculated during a training period, or a non-face detecting period, by a filtering-kernel generator. The filtering kernel is preferably computed utilizing a database of training face images that have been averaged and then masked to remove DC, illumination and noise components.
173 Citations
19 Claims
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1. A method of pre-filtering an input image to determine whether said input image includes a target image pattern of interest comprising steps of:
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receiving said input image;
correlating said input image with preselected reference data to derive a correlation image, said preselected reference data being representative of said target image pattern of interest, said correlation image having image data indicative of correlations between said input image and said preselected reference data; and
selecting a candidate region of said input image having a likelihood of containing said target image pattern of interest on a basis of correlating said input image with said preselected reference data, said step of selecting including identifying potential candidate regions of said input image based on detecting a local maximum in said correlation image and screening said potential candidate regions by analyzing a grayscale characteristic of said potential candidate regions, said screening including discarding said potential candidate regions that do not satisfy a predetermined criterion with respect to said grayscale characteristic in order to increase a probability that said selected candidate region contains said target image pattern of interest. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of pre-filtering an input image to select a candidate region of interest that potentially contains a predetermined image pattern comprising steps of:
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receiving said input image;
examining a grayscale characteristic of a particular image region of said input image as a determination factor in determining whether said particular image region has a likelihood of containing said predetermined image pattern, including comparing a contrast value from a sub-region of said particular image region to a threshold contrast value as a basis for said determination, said particular image region being identified by correlating said input image with a reference image; and
designating said particular image region as said candidate region for said image pattern detection. - View Dependent Claims (10, 11, 12, 13, 14)
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15. An image processing system for detecting a target image pattern in an input image comprising:
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first filtering means configured for identifying a plurality of image regions of said input image that have a likelihood of containing said target image pattern, said filtering means being configured to correlate said input image with a reference image pattern to select said image regions, said reference image pattern being indicative of said target image pattern;
second filtering means operatively coupled to and operatively following said first filtering means for screening said image regions to select a candidate region that has a high likelihood of containing said target image pattern, said second filtering means being configured to examine a grayscale characteristic of said image regions as a determination factor in selecting said candidate region from among said image regions; and
an image pattern detector connected to and operatively following said second filtering means to receive said candidate region, said image pattern detector designed to analyze said candidate region to verify whether said candidate region contains said target image pattern. - View Dependent Claims (16, 17, 18, 19)
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Specification