Digital imaging method and apparatus for detection of document security marks

• US 6,580,820 B1
• Filed: 06/09/1999
• Issued: 06/17/2003
• Est. Priority Date: 06/09/1999
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Fan, Zhigang
• Primary Examiner(s): Au, Amelia M.
• Assistant Examiner(s): MILLER, MARTIN E
• Application Number:
  US09/328,481
• Time in Patent Office: 1,469 Days
• Field of Search: 382/135, 382/137, 382/138, 382/101, 382/216, 382/184, 382/218-221, 382/286, 283/72, 283/114, 283/902, 399/366, 386/94, 705/57, 705/58
• US Class Current: 382/135
• CPC Class Codes: H04N 1/00846 based on detection of a dedicated indication, e.g. marks or the like
• CPC Class Codes: H04N 1/00875 Inhibiting reproduction, e.g. by disabling reading or reproduction apparatus

Abstract

A method and apparatus for preventing or inhibiting effective reproduction of documents such as currency, checks, stock certificates, and any other printed document including a pre-defined security mark printed therein. The subject method and apparatus operate to effect a multi-step review of all digital image data acquired from a printed document to be reproduced for purposes of locating any potential security marks and further examining same for purposes of positively identifying a potential security mark as an actual security mark. If a mark is located and verified to be an authentic security mark, effective reproduction of the printed document will not be permitted and/or other security measures will be taken.

Claims

1. A digital image processing method for preventing unauthorized reproduction of a printed document including a security mark defined in terms of a plurality of actual mark constituents having a select color, select dimensions and arranged in a select pattern relative to each other, said method comprising:

a. scanning said printed document to derive color digital data representing said printed document, said color digital data defined in terms of a plurality of pixels each having a color value;

b. identifying all pixels of said color digital data having a color value representing a color at least approximating said select color of said plurality of actual mark constituents;

c. constructing a binary map of said color digital data defined in terms of “

on” and

“

off”

pixels, said “

on”

pixels corresponding to said identified pixels of said color digital data having color values at least approximating said select color of said plurality of actual mark constituents;

d. using said binary map, identifying potential mark constituents defined by said “

on”

pixels, said step of identifying potential mark constituents by said “

on”

pixels comprising;

processing said pixels of said binary map to identify groups of at least one adjacent “

on”

pixel and identifying each of said groups as a connected component;

comparing dimensions of each connected component to the predefined select dimensions of an actual mark constituent comprising the steps of;

comparing a width of the connected component to minimum and maximum width values of an actual mark constituent;

comparing a height of the connected component to minimum and maximum height values of an actual mark constituent;

only for each connected component having both a width encompassed by said minimum and maximum width values and having a height encompassed by said minimum and maximum height values, comparing the connected component to at least one template, said connected component identified as a potential mark constituent if said connected component matches said at least one template;

e. using said binary map, identifying at least one neighborhood of plural potential mark constituents together defining a potential security mark;

f. identifying said potential security mark as an actual security mark if said potential mark constituents thereof are uniform relative to each other; and

g. preventing effective duplication of said printed document if an actual security mark is identified.

2. The digital image processing method as set forth in claim 1 wherein said step (f) of identifying an actual security mark comprises:

comparing all potential mark constituents of a potential security mark to each other and identifying a potential security mark as an actual security mark if the potential mark constituents defining the potential security mark are uniform relative to each other in terms of at least color and size.

3. A digital image processing method for preventing unauthorized reproduction of a printed document including a security mark defined in terms of a plurality of actual mark constituents having a select color, select dimensions and arranged in a select pattern relative to each other, said method comprising:

a. scanning said printed document to derive color digital data representing said printed document, said color digital data defined in terms of a plurality of pixels each having a color value;

b. identifying all pixels of said color digital data having a color value representing a color at least approximating said select color of said plurality of actual mark constituents;

c. constructing a binary map of said color digital data defined in terms of “

on” and

“

off”

pixels, said “

on”

pixels corresponding to said identified pixels of said color digital data having color values at least approximating said select color of said plurality of actual mark constituents;

d. using said binary map, identifying potential mark constituents defined by said “

on”

pixels;

e. using said binary map, identifying at least one neighborhood of plural potential mark constituents together defining a potential security mark, said step of identifying at least one neighborhood comprising;

establishing a neighborhood about the potential mark constituent;

counting the number of potential mark constituents located in the neighborhood;

comparing the number of potential mark constituents in the neighborhood to the number of potential mark constituents used to define an actual security mark; and

identifying a neighborhood as a potential security mark only if the number of potential mark constituents therein is equal to or greater than the number of actual mark constituents required to define an actual security mark;

f. identifying said potential security mark as an actual security mark if said potential mark constituents thereof are uniform relative to each other; and

g. preventing effective duplication of said printed document if an actual security mark is identified.

4. The digital image processing method as set forth in claim 3 wherein said neighborhood established about each potential mark constituent has a radius based upon a predefined maximum distance between any two actual mark constituents defining an actual security mark in said printed document.

5. The digital image processing method as set forth in claim 3 further comprising, prior to identifying a neighborhood as a potential security mark:

determining the distances between potential mark constituents in said neighborhood; and

identifying a neighborhood as a potential security mark only if the distances between potential mark constituents define a super-set of distances between actual mark constituents of an actual security mark in said printed document.

6. A document reproduction security method comprising:

scanning a printed document to derive color digital image data representative of said printed document;

processing said digital image data to identify all pixels thereof in a select color range used to define a security mark in said printed document;

processing said digital image data to identify all connected components comprising only pixels of said digital image data in said select color range;

processing said digital image data to identify as potential mark constituents all of said connected components having both a size and shape corresponding to a predefined size and shape of actual mark constituents defining said security mark in said printed document;

processing said digital image data to establish a neighborhood of a select size about each potential mark constituent and determining if a number of potential mark constituents in the neighborhood is greater than or equal to a minimum and less than or equal to a maximum number of actual mark constituents;

only for neighborhoods having greater than or equal to a minimum and less than or equal to a maximum number of potential mark constituents required to define a security mark, identifying the neighborhood as a potential security mark if the potential mark constituents in the neighborhood are arranged relative to each other in a manner corresponding to the actual mark constituents defining said security mark in said printed document;

for each neighborhood identified as a potential security mark, processing said digital image data to identify said potential security mark as an actual security mark if said potential mark constituents in said neighborhood are uniform in terms of at least size and color; and

preventing effective reproduction of said printed document if said digital image data comprises an actual security mark.