Method and apparatus for estimating vanish points from an image, computer program and storage medium thereof

• US 8,045,804 B2
• Filed: 11/28/2007
• Issued: 10/25/2011
• Est. Priority Date: 11/29/2006
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Xu, Lifeng, Zeng, Xu, Xiao, Qilin
• Primary Examiner(s): PATEL, KANJIBHAI B
• Application Number:
  US11/946,105
• Publication Number:
  US 20080260256A1
• Time in Patent Office: 1,427 Days
• Field of Search: 382/173, 382/199, 382/275, 382/284, 382/312, 382/314, 382/188, 382/195, 434/85, 434/90, 332/28, 334/32
• US Class Current: 382/188
• CPC Class Codes: G06V 30/1478 of characters or characters lines

Abstract

A method and apparatus for estimating vanishing points from an image, a computer program and a storage medium thereof are provided. One of the methods for detecting the vanishing points from an image includes a dividing step for dividing the image into small patches, a first detecting step for detecting each patch'"'"'s local orientations, a composing step for composing lines of pencils from which at least one vanishing point is to be computed based on the local orientations detected in the first detecting step, and a computing step for computing at least one vanishing point based on the lines of pencils composed in the composing step. On the basis of the computed vanishing points, the perspective rectification on a document image can be executed accurately and quickly.

Claims

1. A method for detecting at least one vanishing point from an image, the method comprising the following steps performed by at least one processor:

a dividing step for dividing the image into a plurality of patches;

a first detecting step for detecting each patch'"'"'s local orientations;

a composing step for composing lines of pencils from which at least one vanishing point is to be computed based on the local orientations detected in said first detecting step; and

a first computing step for computing at least one vanishing point based on the lines of pencils composed in said composing step.

2. A method according to claim 1, further comprising a first pruning step for pruning a noisy line from the lines of pencils composed in said composing step, and wherein, in said first computing step, the vanishing point is computed based on the lines of pencils after the noisy line was pruned in said first pruning step.

3. A method according to claim 1, wherein the local orientations are detected based on local spectra analysis of the patches in said first detecting step.

4. A method according to claim 3, wherein said first detecting step comprises:

a preprocessing step for preprocessing the patches with a spectra filter;

a second computing step for computing the patch'"'"'s spectra by processing the preprocessed patches with FFT;

a second pruning step for adaptively pruning the patch'"'"'s spectra obtained in said second computing step; and

an estimating step for estimating the local orientations by independent component analysis of the spectra.

5. A method according to claim 4, wherein the spectra filter used in said preprocessing step is a Hanning filter.

6. A method according to claim 4, wherein, in said second pruning step, the spectra are pruned by deleting the directed current component and reserving the first “

n”

largest spectra component, wherein the “

n”

equals a template size.

7. An apparatus for detecting at least one vanishing point from an image, the apparatus comprising at least one processor which executes a program stored in a memory, wherein the at least one processor comprises:

a dividing unit configured to divide the image into a plurality of patches;

a first detecting unit configured to detect each patch'"'"'s local orientations;

a composing unit configured to compose lines of pencils from which at least one vanishing point is to be computed based on the local orientations detected by said first detecting unit; and

a first computing unit configured to compute at least one vanishing point based on the lines of pencils composed by said composing unit.

8. A non-transitory computer-readable storage medium storing a computer program, wherein the computer program enables a computer to execute:

a dividing step for dividing the image into a plurality of patches;

a first detecting step for detecting each patch'"'"'s local orientations;

a composing step for composing lines of pencils from which at least one vanishing point is to be computed based on the local orientations detected in said first detecting step; and

a first computing step for computing at least one vanishing point based on the lines of pencils composed in said composing step.