Image correction apparatus and method, image correction database creating method, information data provision apparatus, image processing apparatus, information terminal, and information database apparatus

• US 20070171288A1
• Filed: 03/01/2005
• Published: 07/26/2007
• Est. Priority Date: 03/25/2004
• Status: Abandoned Application

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Mitani, Kenichiro, Tsujita, Kousuke, Takeuchi, Satoru, Kunisa, Akiomi, Inoue, Yasuaki
• Application Number:
  US10/594,151
• Publication Number:
  US 20070171288A1
• Time in Patent Office: Days
• US Class Current: 348/241
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• CPC Class Codes: G06T 2201/0083 whereby only watermarked image required at decoder, e.g. source-based, blind, oblivious
• CPC Class Codes: G06T 3/00 Geometric image transformations in the plane of the image
• CPC Class Codes: H04N 1/32144 embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• CPC Class Codes: H04N 1/32352 Controlling detectability or arrangements to facilitate detection or retrieval of the embedded information, e.g. using markers for decoding, detection or retrieval operations H04N1/32149 and subgroups take precedence
• CPC Class Codes: H04N 1/387 Composing, repositioning or otherwise geometrically modifying originals

Abstract

A capturing unit captures and digitizes a printed image having an electronic watermark embedded therein and a lattice pattern image. A profile creation unit detects position deviations of intersections in the lattice pattern images captured at respective different zoom magnifications, generates correction information on distortion occurring in the images, and registers the correction information into a profile database in association with the zoom magnifications. An image correction unit selects correction information corresponding to a zoom magnification employed at the time of capturing of the printed image from the profile database, and corrects distortion occurring in the captured image of the printed image. An image area determination unit determines an original image area in the distortion-corrected captured image. A watermark extraction unit extracts watermark information from the original image area in the distortion-corrected captured image.

Claims

1. An image correction apparatus comprising:

a lens distortion calculation unit which acquires information on zoom magnifications contained in data of known images captured at respective different zoom magnifications, and calculates lens distortion correction information with respect to each zoom magnification; and

a storing unit which stores the lens distortion correction information in association with the zoom magnifications.

2. An image correction apparatus comprising:

a storing unit which contains lens distortion correction information in association with zoom magnifications of a lens;

a selection unit which acquires from data of an input captured image, information on a zoom magnification employed at the time of capturing of the captured image, and selects lens distortion correction information corresponding to the zoom magnification from the storing unit; and

a distortion correction unit which corrects distortion of the captured image ascribable to capturing based on the lens distortion correction information selected.

3. The image correction apparatus according to claim 2, wherein

the selection unit selects from the storing unit a plurality of candidate pieces of lens distortion correction information in accordance with the zoom magnification employed at the time of capturing, and correct a row of sample points forming a known shape in the captured image by using each of the plurality of pieces of lens distortion correction information for error pre-evaluation, and thereby selects one piece of lens distortion correction information from among the plurality of pieces of lens distortion correction information.

4. An image correction apparatus comprising:

a lens distortion calculation unit which acquires information on zoom magnifications contained in data of known images captured at respective different zoom magnifications, and calculates a lens distortion correction function for mapping points in a lens-distorted image onto points in an image having no lens distortion and a lens distortion function, or an approximate inverse function of the lens distortion correction function, with respect to each lens magnification; and

a storing unit which stores the pairs of lens distortion correction functions and lens distortion functions in association with the zoom magnifications.

5. An image correction apparatus comprising:

a storing unit which contains pairs of lens distortion correction functions for mapping points in a lens-distorted image onto points in an image having no lens distortion and lens distortion functions, that are approximate inverse functions of the lens distortion correction functions, in association with respective zoom magnifications of a lens;

a selection unit which acquires from data of an input captured image, information on a zoom magnification employed at the time of capturing of the captured image, and selects from the storing unit the lens distortion function corresponding to the zoom magnification; and

a distortion correction unit which corrects distortion of the captured image ascribable to capturing based on the lens distortion function selected.

6. The image correction apparatus according to claim 5, wherein

the selector unit selects from the memory unit a plurality of candidate lens distortion correction functions in accordance with the zoom magnification employed at the time of capturing, and corrects a sequence of sample points forming a known shape in the captured image by using each of the plurality of lens distortion correction functions for error pre-evaluation, and thereby selects one of the plurality of lens distortion functions.

7. An image correction apparatus comprising:

a storing unit which contains lens distortion functions for mapping points in an image having no lens distortion onto points in a lens-distorted image in association with respective zoom magnifications of a lens;

a selection unit which acquires from data of an input captured image, information on a zoom magnification employed at the time of capturing of the captured image, and selects the lens distortion function corresponding to the zoom magnification from the storing unit;

a perspective distortion calculation unit which calculates a perspective distortion function for mapping points in an image having no perspective distortion onto points on a perspective-distorted image, by using an image whose lens distortion is corrected by the lens distortion function selected; and

a distortion correction unit which corrects distortion of the captured image ascribable to capturing based on the perspective distortion function calculated by the perspective distortion calculation unit.

8. The image correction apparatus according to claim 7, wherein

the selector unit selects from the memory unit a plurality of candidate lens distortion correction functions in accordance with the zoom magnification employed at the time of capturing, and corrects a sequence of sample points forming a known shape in the captured image by using each of the plurality of lens distortion correction functions for error pre-evaluation, and thereby selects one of the plurality of lens distortion functions.

9. An image correction database creating method comprising:

acquiring information on zoom magnifications contained in data of known images captured at the respective different zoom magnifications, and calculating a lens distortion correction function for mapping points on a lens-distorted image onto points on an image having no lens distortion and a lens distortion function, or an approximate inverse function of the lens distortion correction function, with respect to each lens magnification; and

registering the pairs of lens distortion correction functions and lens distortion functions into a database in association with the zoom magnifications.

10. An image correction method comprising:

consulting a database in which pairs of lens distortion correction functions for mapping points in a lens-distorted image onto points in an image having no lens distortion and lens distortion functions, that are approximate inverse functions of the lens distortion correction functions, are registered in association with respective zoom magnifications of a lens, acquiring from data of an input captured image, information on a zoom magnification employed at the time of capturing of the captured image, and selecting the lens distortion function corresponding to the zoom magnification; and

correcting distortion of the captured image ascribable to capturing based on the lens distortion function selected.

11. The image correction method according to claim 10, wherein

the correcting of the distortion includes:

mapping a point in a target image having no distortion ascribable to capturing onto a point in a lens-distorted captured image by using the lens distortion function selected which was selected from the image correction database; and

determining a pixel value at the point in the target image by interpolating pixel values near the mapped point in the captured image.

12. The image correction method according to claim 10 or 11, wherein

the selecting of the lens distortion function includes:

selecting a plurality of lens distortion correction functions as candidates in accordance with the zoom magnification employed at the time of capturing;

correcting a row of sample points having a known shape in the captured image by each of the plurality of lens distortion correction functions for error pre-evaluation; and

selecting one from among the plurality of lens distortion functions.

13. An image correction method comprising:

consulting a database in which lens distortion functions for mapping points in an image having no lens distortion onto points in a lens-distorted image are registered in association with respective zoom magnifications of a lens, and acquiring from data of an input captured image, a zoom magnification employed at the time of capturing of the captured image and selecting the lens distortion function corresponding to the zoom magnification;

calculating a perspective distortion function for mapping points in an image having no perspective distortion onto points in a perspective-distorted image, by using an image whose lens distortion is corrected by the lens distortion function selected; and

correcting distortion of the captured image ascribable to capturing based on the perspective distortion function calculated.

14. The image correction method according to claim 13, wherein

the correcting of the distortion includes:

mapping a point in a target image having no distortion ascribable to capturing onto a point in a perspective-distorted captured image by using the perspective distortion function calculated; and

determining a pixel value at the point in the target image by interpolating pixel values near the mapped point in the captured image.

15. The image correction method according to claim 13 or 14, wherein

the selecting of the lens distortion function includes:

selecting a plurality of lens distortion correction functions as candidates in accordance with the zoom magnification employed at the time of capturing;

correcting a row of sample points having a known shape in the captured image by each of the plurality of lens distortion correction functions for error pre-evaluation; and

thereby selecting one from among the plurality of lens distortion functions.

16-24. -24. (canceled)