SYSTEMS AND METHODS FOR THREE DIMENSIONAL GEOMETRIC RECONSTRUCTION OF CAPTURED IMAGE DATA

• US 20150093018A1
• Filed: 09/19/2014
• Published: 04/02/2015
• Est. Priority Date: 09/27/2013
• Status: Active Grant

• Current Assignee: Kofax Incorporated
• Original Assignee: Kofax Incorporated
• Inventors: Macciola, Anthony, Ma, Jiyong, Shustorovich, Alexander, Thrasher, Christopher W., Amtrup, Jan
• Granted Patent: US 9,208,536 B2
• Time in Patent Office: Days
• US Class Current: 382/154
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G06T 2207/30176 Document
• CPC Class Codes: G06T 3/00 Geometric image transformations in the plane of the image
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes

Abstract

In various embodiments, methods, systems, and computer program products for processing digital images captured by a mobile device are disclosed. Myriad features enable and/or facilitate processing of such digital images using a mobile device that would otherwise be technically impossible or impractical, and furthermore address unique challenges presented by images captured using a camera rather than a traditional flat-bed scanner, paper-feed scanner, or multifunction peripheral. Notably, the presently disclosed systems and techniques enable three-dimensional reconstruction of objects depicted in image captured using a camera of a mobile device. The reconstruction corrects or compensates for perspective distortion caused by camera-based capture.

Claims

1. A method of reconstructing a digital image, the method comprising:

receiving the digital image comprising a digital representation of an object bounded by a tetragon;

correcting curvature in the tetragon to form a quadrilateral; and

correcting projective effects in the quadrilateral to form a rectangle.

2. The method as recited in claim 1, wherein the quadrilateral is a parallelogram.

3. The method as recited in claim 1, wherein correcting the curvature comprises transforming one or more portions of the tetragon based at least in part on intrinsic tetragon coordinates.

4. The method as recited in claim 1, wherein correcting the projective effects comprises transforming the tetragon using a four-point algorithm.

5. The method as recited in claim 1, wherein the digital image is characterized by a capture angle of about 30 degrees or more deviation from normal with respect to the object.

6. The method as recited in claim 1, wherein correcting the projective effects comprises singular value decomposition (SVD).

7. The method as recited in claim 1, wherein correcting the projective effects comprises direct linear transformation (DLT).

8. The method as recited in claim 1, wherein correcting the projective effects comprises estimating a homography transform H.

9. The method as recited in claim 8, wherein estimating H comprises detecting one or more point correspondences p_iP_i′

with p_i=(x_i,y_i,1)^T.

10. The method as recited in claim 9, wherein estimating H comprises detecting four point correspondences, each point correspondence p_iP_i′

corresponding to a corner position p_i of the tetragon and a respective corner position P′

_i of the rectangle.

11. The method as recited in claim 8, wherein H satisfies the expression λ

p_i=HP_i′

, where

λ

=a focal distance between a three-dimensional reference coordinate position (X, Y, Z) and a corresponding reference coordinate position of a capture device;

p_i=(x_i,y_i,1)^T;

P′

_I=(X_i,Y_i,1)^T, and

i is the respective index feature of the point p or P′

in the corresponding image.

12. The method as recited in claim 1, wherein correcting the projective effects comprises performing a non-linear refinement.

13. The method as recited in claim 1, further comprising outputting the reconstructed digital image, wherein the reconstructed digital image is characterized by a pixel location error of about 5 pixels or less relative to a scanned 500-DPI image of the object captured using a capture angle normal to the object.

14. The method as recited in claim 1, wherein at least one side of the tetragon is characterized by a second degree or higher order polynomial.

15. The method as recited in claim 14, wherein each side of the tetragon is characterized by a second degree or higher order polynomial.

16. The method as recited in claim 1, wherein correcting the projective effects comprises normalizing coordinates of point-correspondences between the digital image and a reconstructed image.

17. The method as recited in claim 1, wherein the object is a document characterized by a known height-to-width ratio.

18. A system, comprising:

a processor configured to execute logic; and

logic configured to receive a digital image comprising a digital representation of an object bounded by a tetragon;

logic configured to correct curvature in the tetragon to form a quadrilateral; and

logic configured to correct projective effects in the quadrilateral to form a rectangle.

19. A computer program product comprising a computer readable storage medium having computer readable program code stored thereon, the computer readable program code comprising:

computer readable program code configured to receive a digital image comprising a digital representation of an object bounded by a tetragon;

computer readable program code configured to correct curvature in the tetragon to form a quadrilateral; and

computer readable program code configured to correct projective effects in the quadrilateral to form a rectangle.