METHOD FOR DETECTING BLANK PAGES, AND CORRESPONDING MULTIFUNCTIONAL MACHINE

• US 20120170082A1
• Filed: 09/10/2010
• Published: 07/05/2012
• Est. Priority Date: 09/10/2009
• Status: Active Grant

• Current Assignee: Sagemcom Documents SAS (Sagemcom Holding SAS)
• Original Assignee: Sagemcom Documents SAS (Sagemcom Holding SAS)
• Inventors: Labois, Olivier, Sabatier, Pierre, Berger, Jérôme
• Granted Patent: US 8,724,182 B2
• Time in Patent Office: Days
• US Class Current: 358/474
• CPC Class Codes: G06V 10/28 Quantising the image, e.g. histogram thresholding for discrimination between background and foreground patterns
• CPC Class Codes: G06V 30/422 Technical drawings; Geographical maps
• CPC Class Codes: H04N 1/00795 Reading arrangements details of scanning heads H04N1/024; scanning arrangements therefor H04N1/04
• CPC Class Codes: H04N 1/00803 Presence or absence of information
• CPC Class Codes: H04N 2201/0094 Multifunctional device, i.e. a device capable of all of reading, reproducing, copying, facsimile transception, file transception

Abstract

The invention relates to a method for detecting blank pages among sheets of a document scanned on a multifunctional machine comprising a scanner, wherein said scanner: scans (S0) two pages of at least one sheet of a document to be scanned; carries out a basic detection (S6) of a blank page on each scanned sheet; selects (S7) each sheet not comprising at least one page detected to be blank during the detection (S6); compares (S9) the two pages of said selected sheet; and classifies (S9) a page as blank when it is similar to the other page of said sheet. The invention also relates to a multifunctional machine, the machine comprising a scanner for implementing a method according to the invention.

Claims

1. A method for detecting blank pages in the sheets of a document scanned on a machine (1) including a scanner (2), wherein the scanner (2)

scans (S0) two pages of at least one sheet of a document to be scanned;

performs at least one blank page detection (S6) on each scanned sheet;

selects (S7) each sheet not having at least one page detected as blank during the detection (S6);

characterized in that the scanner compares (S9) the two pages of said selected sheet, and classifies (S9) a page as blank when a datum characteristic of the similarity of said page to the other page exceeds a similarity criterion.

2. A method according to claim 1, wherein the scanner

scans (S0) the pages to transform each page into a set of pixels belonging to ^é

the space of real numbers, and transposes (S2) each pixel so that it has a gray level, and

also performs, prior to the selection (S7) of each sheet not having at least one page detected as blank, a binarisation (S5) of the pixels of the pages of each sheet, the binarisation consisting of assigning

an active value to each pixel the gray level whereof exceeds a threshold τ

, and

an inactive value to a pixel the gray level whereof is below the threshold τ

,

where τ

is defined dynamically according to the neighborhood of the pixel.

3. A method according to claim 2, wherein,

the scanner assigns (S8), subsequent to the binarisation (S5), the front page R of a sheet to the page having the greater probability of being information-bearing, the scanner assigning the back page V to the other page of the sheet, and wherein, to perform the step of comparison between the two pages,

the scanner (2) constructs first of all a local dissimilarities map CDL, made up of pixels CDL(x) having a position x, the value of each pixel CDL(x) being given by the formula:

∀

xε

^é

,CDL(x)=( R(x)·

V(x)·

d(x,R)

where

x represents the position of the pixel on a page;

V(x) is the value of the pixel of the back page at the position x;

R(x) is the inverse of the value of the front page pixel at the position x;

( R(x)·

V(x)) is equivalent to a logical AND operator

d(x,R) is the minimum distance calculated between the position x and the pixels of the front page having an active value;

the scanner (2) then constructs a histogram collecting all the pixels CDL(x) having the same value, for each value of CDL(x), and

the scanner (2) considers that the front R and back V pages are similar when the number of pixels of the local dissimilarities map CDL, the value whereof is less than a predetermined distance value d, is greater than a proportion H, and thus classifies (S9) the corresponding back page V as a blank page.

4. A method according to claim 3, wherein the scanner (2) calculates d(x,R) using the so-called Manhattan distance.

5. A method according to one of claims 3 or 4, wherein the predetermined distance value d corresponds to a reference distance d(x,R) of three pixels, the proportion H being 70% of the pixels of the local dissimilarities map.

6. A method according to one of claims 3 through 5 wherein, during the calculation of the distance d(x,R), the scanner directly assigns the value (d+1) to the pixel CDL(x) whenever the distance d(x,R) strictly exceeds the reference distance at the point x, and stops the corresponding distance calculation.

7. A method according to one of claims 1 through 6, wherein the step of at least one blank page detection on each scanned sheet comprises steps whereby the scanner (2)

performs a first blank page or information-bearing page detection (S3) on each scanned page, in gray levels;

and

selects (S4) each sheet every page whereof has not been detected as blank or information-bearing during the first detection (S3).

8. A method according to one of claims 3 through 7, wherein the step consisting of at least one blank page detection on each scanned sheet comprises, subsequent to the binarisation (S5), as step whereby the scanner (2) performs a second blank page or information-bearing page detection (S6) on each binarised page, the step (S8) of assigning a front page and an back page being then carried out on each sheet not having at least one page detected as blank during the second detection (S6).

9. A method according to one of claims 1 through 8, wherein the scanner (2) performs a step (S2) of edge suppression and/or size readjustment and/or transposition into gray levels on the scanned pages.

10. A machine (1), characterized in that it includes a scanner (2) implementing a method according to one of claims 1 through 9.