Shadow detection in images
First Claim
Patent Images
1. A process comprising:
- capturing a reference image;
capturing a current image;
calculating reference image to current image object plus shadow ratios (RTOPS);
calculating reference image to current image object ratios (RTO);
calculating reference image to current image shadow ratios (RTS);
calculating an average RTOPS ratio;
calculating an average RTO ratio;
calculating an average RTS ratio;
calculating a first range using said RTOPS, RTO, and RTS ratios; and
identifying a pixel as being under a shadow by multiplying a lower limit of said first range by said average RTOPS ratio and multiplying an upper limit of said first range by said average RTOPS ratio, thereby giving a second range; and
determining whether said pixel falls within said second range.
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Abstract
In an embodiment, a novel, scene adaptive, robust shadow detection method has been disclosed. An adaptive division image analysis compares one or more images containing objects and shadows to a reference image that is void of the objects and shadows. Ratios are calculated comparing the frame with shadows and/or objects to the reference frame. Shadows are identified by identifying pixels that fall within a certain range of these ratios. In another embodiment, projection histograms are used to identify the penumbra region of shadows in the image.
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Citations
20 Claims
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1. A process comprising:
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capturing a reference image;
capturing a current image;
calculating reference image to current image object plus shadow ratios (RTOPS);
calculating reference image to current image object ratios (RTO);
calculating reference image to current image shadow ratios (RTS);
calculating an average RTOPS ratio;
calculating an average RTO ratio;
calculating an average RTS ratio;
calculating a first range using said RTOPS, RTO, and RTS ratios; and
identifying a pixel as being under a shadow by multiplying a lower limit of said first range by said average RTOPS ratio and multiplying an upper limit of said first range by said average RTOPS ratio, thereby giving a second range; and
determining whether said pixel falls within said second range. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A process comprising:
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capturing a reference image;
capturing a current image;
identifying a shadow in said current image using an adaptive image division analysis; and
identifying penumbra of said shadow using a projection histogram analysis. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A machine readable medium comprising instructions thereon for executing a process comprising:
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capturing a reference image;
capturing a current image;
calculating reference image to current image object plus shadow ratios (RTOPS);
calculating reference image to current image object ratios (RTO);
calculating reference image to current image shadow ratios (RTS);
calculating an average RTOPS ratio;
calculating an average RTO ratio;
calculating an average RTS ratio;
calculating a first range using said RTOPS, RTO, and RTS ratios; and
identifying a pixel as being under a shadow by multiplying a lower limit of said first range by said average RTOPS ratio and multiplying an upper limit of said first range by said average RTOPS ratio, thereby giving a second range; and
determining whether said pixel falls within said second range. - View Dependent Claims (17, 18, 19, 20)
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Specification