Method and apparatus for authenticating printed documents that contains both dark and halftone text
First Claim
1. A document authentication method implemented in a data processing system, comprising:
- (a) obtaining an original grayscale image representing an original document, the original grayscale image including one or more halftone text areas or light text areas and one or more non-halftone text areas or dark text areas, wherein each halftone text area includes a plurality of halftone dots, each halftone dot being formed by a plurality of pixels, each pixel being a smallest unit of the original grayscale image and each pixel having a grayscale pixel value;
(b) separating the halftone or light text areas from the non-halftone or dark text areas of the original grayscale image;
(c) separately binarizing the halftone or light text areas and the non-halftone or dark text areas generated by step (b);
(d) down-sampling only the binarized non-halftone or dark text areas generated by step (c) which correspond to the non-halftone or dark text areas of the original grayscale image, without down-sampling the binarized halftone or light text areas which correspond to the halftone or light text areas of the same original grayscale image, whereby a binarized original image is generated;
(e) obtaining a target grayscale image representing a hardcopy target document, the target grayscale image including one or more halftone text areas and one or more non-halftone text areas, wherein each halftone text area includes a plurality of halftone dots, each halftone dot being formed by a plurality of pixels, each pixel being a smallest unit of the target grayscale image and each pixel having a grayscale pixel value;
(f) separating the halftone text areas and the non-halftone text areas of the target grayscale image;
(g) separately binarizing the halftone text areas and the non-halftone text areas generated by step (f);
(h) down-sampling only the binarized non-halftone text areas generated by step (g) which correspond to the non-halftone text areas of the target grayscale image, without down-sampling the binarized halftone text areas which correspond to the halftone text areas of the same target grayscale image, whereby a binarized target image is generated; and
(i) comparing the binarized target image with the binarized original image to determine whether the target document is an authentic copy of the original document.
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Accused Products
Abstract
A document authentication method determines the authenticity of a target hardcopy document, which purports to be a true copy of an original hardcopy document. The method compares a binarized image of the target document with a binarized image of the original document which has been stored in a storage device. The image of the original document is generated by binarizing a scanned grayscale image of the original document. Halftone and non-halftone text areas in the grayscale image area separated, and the two types of text are separately binarized. The non-halftone text areas are then down-sampled. During authenticating, a scanned grayscale image of the target document is binarized by separating halftone and non-halftone text areas and binarizing them separately, and then down-sampling the non-halftone text areas. The binarized images of the target document and the original document are compared to determine the authenticity of the target document.
25 Citations
16 Claims
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1. A document authentication method implemented in a data processing system, comprising:
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(a) obtaining an original grayscale image representing an original document, the original grayscale image including one or more halftone text areas or light text areas and one or more non-halftone text areas or dark text areas, wherein each halftone text area includes a plurality of halftone dots, each halftone dot being formed by a plurality of pixels, each pixel being a smallest unit of the original grayscale image and each pixel having a grayscale pixel value; (b) separating the halftone or light text areas from the non-halftone or dark text areas of the original grayscale image; (c) separately binarizing the halftone or light text areas and the non-halftone or dark text areas generated by step (b); (d) down-sampling only the binarized non-halftone or dark text areas generated by step (c) which correspond to the non-halftone or dark text areas of the original grayscale image, without down-sampling the binarized halftone or light text areas which correspond to the halftone or light text areas of the same original grayscale image, whereby a binarized original image is generated; (e) obtaining a target grayscale image representing a hardcopy target document, the target grayscale image including one or more halftone text areas and one or more non-halftone text areas, wherein each halftone text area includes a plurality of halftone dots, each halftone dot being formed by a plurality of pixels, each pixel being a smallest unit of the target grayscale image and each pixel having a grayscale pixel value; (f) separating the halftone text areas and the non-halftone text areas of the target grayscale image; (g) separately binarizing the halftone text areas and the non-halftone text areas generated by step (f); (h) down-sampling only the binarized non-halftone text areas generated by step (g) which correspond to the non-halftone text areas of the target grayscale image, without down-sampling the binarized halftone text areas which correspond to the halftone text areas of the same target grayscale image, whereby a binarized target image is generated; and (i) comparing the binarized target image with the binarized original image to determine whether the target document is an authentic copy of the original document. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A computer program product comprising a computer usable non-transitory medium having a computer readable program code embedded therein for controlling a data processing apparatus, the computer readable program code configured to cause the data processing apparatus to execute a document authentication process which comprises:
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(a) obtaining an original grayscale image representing an original document, the original grayscale image including one or more halftone text areas and one or more non-halftone text areas, wherein each halftone text area includes a plurality of halftone dots, each halftone dot being formed by a plurality of pixels, each pixel being a smallest unit of the original grayscale image and each pixel having a grayscale pixel value; (b) separating the halftone text areas and the non-halftone text areas of the original grayscale image; (c) separately binarizing the halftone text areas and the non-halftone text areas generated by step (b); and (d) down-sampling only the binarized non-halftone or dark text areas generated by step (c) which correspond to the non-halftone or dark text areas of the original grayscale image, without down-sampling the binarized halftone or light text areas which correspond to the halftone or light text areas of the same original grayscale image, whereby a binarized original image is generated. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A computer program product comprising a computer usable non-transitory medium having a computer readable program code embedded therein for controlling a data processing apparatus, the computer readable program code configured to cause the data processing apparatus to execute a document authentication process which comprises:
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(a) obtaining a target grayscale image representing a hardcopy target document, the target grayscale image including one or more halftone text areas and one or more non-halftone text areas, wherein each halftone text area includes a plurality of halftone dots, each halftone dot being formed by a plurality of pixels, each pixel being a smallest unit of the original grayscale image and each pixel having a grayscale pixel value; (b) separating the halftone text areas and the non-halftone text areas of the target grayscale image; (c) separately binarizing the halftone text areas and the non-halftone text areas generated by step (b); (d) down-sampling only the binarized non-halftone text areas generated by step (c) which correspond to the non-halftone text areas of the target grayscale image, without down-sampling the binarized halftone text areas which correspond to the halftone text areas of the same target grayscale image, whereby a binarized target image is generated; and (e) comparing the binarized target image with a binarized image of an original document to determine whether the target document is an authentic copy of the original document. - View Dependent Claims (15, 16)
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Specification