Document alteration indicating system and method
AssigneeInternational Business Machines Corporation
InventorRavi Prakash
Life of this patent
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Abstract
A system and method for detecting alteration of a document. The invention evaluates markings in half-tone fields by ascertaining a first dot count of dots isolated from the marking in the half-tone field of the document; forming an image of the marking; superimposing the image on a blank half-tone field having the same predetermined pattern as the half-tone field of the document; ascertaining a second dot count of dots isolated from the image superimposed on the blank half-tone field; and determining whether the marking has been altered by comparing the first dot count to the second dot count. An alteration is indicated where the first dot count and second clot count are different.
Claims18
A method of detecting alteration of a marking in a half-tone field of a document, the half-tone field having a predetermined pattern, the method comprising the steps of:
- ascertaining a first dot count of dots isolated from the marking in the half-tone field of the document;
- forming an image of the marking;
- superimposing the image on a blank half-tone field having the same predetermined pattern as the half-tone field of the document;
- ascertaining a second dot count of dots isolated from the image superimposed on the blank half-tone field;
- and
- determining whether the marking has been altered by comparing the first dot count to the second dot count,
- wherein an alteration of the marking is indicated when the first dot count is different than the second dot count.
A system for indicating alteration of a marking of a document half-tone field, the document half-tone field having a predetermined pattern, the system comprising:
- a dot counter for counting isolated dots of a half-tone field;
- an imager for forming an image of the marking of the document half-tone field;
- a superimposer for superimposing the image on a blank half-tone field having the same predetermined pattern as the document half-tone field;
- a comparator for comparing a first dot count of the document half-tone field to a second dot count of the blank half-tone field with the image superimposed thereon,
- wherein an alteration is indicated when the first dot count is different than the second dot count.
A computer program product comprising a computer useable medium having computer readable program code embodied therein for indicating an alteration of a marking on a document half-tone field, the document half-tone field having a predetermined pattern, the computer program product comprising:
- program code configured to count isolated dots of a half-tone field;
- program code configured to form an image of the marking of the document half-tone field;
- program code configured to superimpose the image on a blank half-tone field having the same predetermined pattern as the document half-tone field;
- and
- program code configured to compare a first dot count of the document half-tone field to a second (lot count of the blank half-tone field with the image superimposed thereon,
- wherein an alteration is indicated when the first dot count is different than the second dot count.
Dependencies are inferred from the claim text.