Method and device for the correction of a scanned image

• US 20050053304A1
• Filed: 07/10/2002
• Published: 03/10/2005
• Est. Priority Date: 11/15/2001
• Status: Abandoned Application

• Current Assignee: Captaris Document Technologies GmbH (Open Text Corporation)
• Original Assignee: Captaris Document Technologies GmbH (Open Text Corporation)
• Inventors: Frei, Bernhard
• Application Number:
  US10/495,795
• Publication Number:
  US 20050053304A1
• Time in Patent Office: Days
• US Class Current: 382/257
• CPC Class Codes: G06T 3/06 Topological mapping of higher dimensional structures onto lower dimensional surfaces

Abstract

A method and apparatus for correcting a scanned image of a non-planar original that has a constant cross section in one direction, such as a book, provides for applying a coordinate system to the scanned image to align the coordinate system to the direction with the constant cross section. The scanned image is imaged onto a target image, or vise versa, using aspect factors or dilation factors. A single calculation is possible to map an image point from the scanned image to the target image and thereby remove the distortion of the non-planar original.

Claims

1-13. -13. (Cancelled).

14. A method to correct a scanned image of a non-planar original that has a constant cross-section contour in one direction, the non-planar original being scanned by a stationary objective to provide a scanned image as a source image, comprising the steps of:

mapping the source image to a Cartesian coordinate system, said mapping including arranging one line of the source image that runs parallel to the constant cross-section contour parallel to an x-axis; and

mapping points of the source image Pq(xq,yq) to points of the target image Pz(xz,yz) or vice versa according to a formula

$\left(\begin{array}{c}\mathrm{xq}\\ \mathrm{yq}\end{array}\right)=\left(\begin{array}{c}\mathrm{sx}\\ \mathrm{sy}\end{array}\right)·<br><br>\left(\begin{array}{c}\mathrm{xz}\\ \mathrm{yz}\end{array}\right),$

wherein sx is an x-dilation factor in an x-direction and sy is a y-dilation factor in a y-direction.

15. A method according to claim 14, further comprising the steps of:

positioning an intersection point of the source image with an optical axis of the objective on the x-axis in said step of mapping of the source image.

16. A method according to claim 14, wherein said object to be scanned is an opened book.

17. A method according to claim 14, wherein said mapping of the source image step includes mapping the source image with its left edge on a y-axis in said step of mapping of the source image to the Cartesian coordinate system.

18. A method according to claim 14, further comprising the steps of:

dividing the source image and the target image into pixels that are arranged in columns running parallel to a y-axis and rows running parallel to the x-axis; and

storing one x-dilation factor and one y-dilation factor for each column.

19. A method according to claim 18, further comprising the steps of:

mapping pixels of the target image to points of the source image;

interpolating image points of the source image to respective points so that color saturation of the respective points of the source image ensues; and

transferring of the color saturation to the image points of the target image.

20. A method according to claim 14, further comprising the step of:

executing said mapping step to the Cartesian coordinate system and said mapping step of the points of the source image to the points of the target image or vice versa with a single calculation operation.

21. A method according to claim 20, wherein said step of mapping of the points of the source image the points of the target image ensues via multiplication of the points of the source image with the following matrix

$(\begin{array}{c}\cos \end{array}$

 

⁢

φ

sin ⁢

 

⁢

φ

·

sx xv1 + xv2 ·

cos ⁢

 

⁢

φ

·

sx + yv2 ·

sin ⁢

 

⁢

φ

·

sx sin ⁢

 

⁢

φ

·

sy cos ⁢

 

⁢

φ

·

sy yv1 + yv2 ·

cos ⁢

 

⁢

φ

·

sy - xv2 ·

sin ⁢

 

⁢

φ

·

sy 0 0 1 ) ,

where xv1 and yv1 are displacement parameters to displace the source image with the projection center of the objective on the x-axis, φ

is the angle by which the source image must be rotated so that its fold runs parallel to the y-axis, xv2 and yv2 are displacement parameters to displace the rotated image by a predetermined vector.

22. A method according to claim 20, wherein said steps of mapping of the points of the target image to the points of the source image ensues via multiplication of the points of the target image with the following matrix

$[\begin{array}{c}\frac{\cos }{}\end{array}$

 

⁢

φ

sx - sin ⁢

 

⁢

φ

sy - xv2 - xv1 ·

cos ⁢

 

⁢

φ

sx + yv1 ·

sin ⁢

 

⁢

φ

sy sin ⁢

 

⁢

φ

sx cos ⁢

 

⁢

φ

sy - yv2 - yv1 ·

sin ⁢

 

⁢

φ

sx + yz1 ·

cos ⁢

 

⁢

φ

sy 0 0 1 ] ,

where xv1 and yv1 are displacement parameters to displace the source image with the projection center of the objective on the x-axis, φ

is the angle by which the source image must be rotated so that its fold runs parallel to the y-axis, xv2 and yv2 are displacement parameters to displace the rotated image by a predetermined vector.

23. A method according to claim 14, wherein the x-dilation factors and y-dilation factors are integer numbers with a precision of at least 16 bits.

24. A device to correct a scanned image of a non-planar original with a constant cross-section contour in one direction, a source image being mapped to a Cartesian coordinate system with one line of a source image running parallel to the constant cross-section contour being arranged parallel to an x-axis of the Cartesian coordinate system, and points of the source image being mapped to points of a target image or vise versa according to a formula

$\left(\begin{array}{c}\mathrm{xq}\\ \mathrm{yq}\end{array}\right)=\left(\begin{array}{c}\mathrm{sx}\\ \mathrm{sy}\end{array}\right)·$

( xz yz ) ,

wherein sx is an x-dilation factor in an x-direction and sy is a y-dilation factor in a y-direction, comprising;

a counter to count the columns of the target image;

a counter to count the rows of the target image;

a storage device to store dilation factors, parameters and values of cos φ and

sin φ

;

a plurality of adder devices and multiplier devices that are connected such that corresponding coordinates of the source image are output dependent on the respective state of both said counters.

25. A device according to claim 24, wherein said plurality of the adder devices and multiplier devices are fashioned to only execute whole-number calculation operations.

26. A computer program product to execute a method to correct a scanned image of a non-planar original with a constant cross-section contour in one direction, comprising the steps of:

arranging the non-planar object to be scanned to be stationary;

scanning the non-planar object to provide a scanned image;

mapping the source image to a Cartesian coordinate system, said mapping including arranging one line of the source image that runs parallel to the constant cross-section contour parallel to an x-axis; and

mapping points of the source image Pq(xq,yq) to points of the target image Pz(xz,yz) or vice versa according to a formula

$\left(\begin{array}{c}\mathrm{xq}\\ \mathrm{yq}\end{array}\right)=\left(\begin{array}{c}\mathrm{sx}\\ \mathrm{sy}\end{array}\right)·<br><br>\left(\begin{array}{c}\mathrm{xz}\\ \mathrm{yz}\end{array}\right),$

wherein sx is an x-dilation factor in an x-direction and sy is a y-dilation factor in a y-direction.