STAIN DETECTION
First Claim
1. A method of detecting staining on a media item, the method comprising:
- receiving an image of the media item, where the image comprises a plurality of pixels having different intensity values within a range of intensity values;
using pixels from the image having intensity values within a central portion of the range of intensity values to create a centrally-weighted image;
applying a threshold to each pixel in the centrally-weighted image to transform each pixel to a binary value thereby creating an evaluation image comprising a plurality of pixels, each having one of two possible values;
calculating a difference image between a binary reference image and the evaluation image by comparing a pixel in the evaluation image with a pixel in the binary reference image at a corresponding spatial location, so that the difference image includes (i) a stain pixel at each spatial location in which a pixel in the evaluation image has a low intensity pixel and the corresponding pixel in the binary reference image has a high intensity pixel, and (ii) a non-stain pixel at all other spatial locations;
indicating that the media item is stained in the event that the difference image meets a staining criterion.
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Abstract
A method of detecting staining on a media item is described. An example method includes receiving an image of the media item, including a plurality of pixels having different intensity values within a range of intensity values, applying central weighting to the received image, applying a threshold to each pixel in the centrally-weighted image to transform each pixel to a binary value, comparing a pixel in the evaluation image with a pixel in a binary reference image to create a difference image including (i) a stain pixel at each spatial location in which a pixel in the evaluation image has a low intensity pixel and the corresponding pixel in the binary reference image has a high intensity pixel, and (ii) a non-stain pixel at all other spatial locations. The media item is identified as stained in the event that the difference image meets a staining criterion.
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Citations
15 Claims
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1. A method of detecting staining on a media item, the method comprising:
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receiving an image of the media item, where the image comprises a plurality of pixels having different intensity values within a range of intensity values; using pixels from the image having intensity values within a central portion of the range of intensity values to create a centrally-weighted image; applying a threshold to each pixel in the centrally-weighted image to transform each pixel to a binary value thereby creating an evaluation image comprising a plurality of pixels, each having one of two possible values; calculating a difference image between a binary reference image and the evaluation image by comparing a pixel in the evaluation image with a pixel in the binary reference image at a corresponding spatial location, so that the difference image includes (i) a stain pixel at each spatial location in which a pixel in the evaluation image has a low intensity pixel and the corresponding pixel in the binary reference image has a high intensity pixel, and (ii) a non-stain pixel at all other spatial locations; indicating that the media item is stained in the event that the difference image meets a staining criterion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A media validator operable to detect staining on a media item presented thereto, the media validator comprising:
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a media item transport for transporting a media item; an image capture device aligned with the media item transport and for capturing a two-dimensional array of pixels corresponding to the media item, each pixel having a pixel intensity relating to a property of the media item at a spatial location on the media item corresponding to that pixel; and a processor programmed to control the media transport and the image capture device, and also programmed to;
(i) receive the two-dimensional array of pixels;
(ii) centrally-weight the received two-dimensional array of pixels;
(iii) apply a threshold to each pixel in the centrally-weighted array of pixels to transform each pixel to a binary value thereby creating an evaluation image comprising a plurality of pixels, each having one of two possible values;
(iv) calculate a difference image between a binary reference image and the evaluation image by comparing a pixel in the evaluation image with a pixel in the binary reference image at a corresponding spatial location, so that the difference image includes (a) a stain pixel at each spatial location in which a pixel in the evaluation image has a low intensity pixel and the corresponding pixel in the binary reference image has a high intensity pixel, and (b) a non-stain pixel at all other spatial locations; and
(v) indicate that the media item is stained in the event that the difference image meets a staining criterion. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification