Method and apparatus for determining projection area of image

• US 8,861,892 B2
• Filed: 11/01/2012
• Issued: 10/14/2014
• Est. Priority Date: 11/11/2011
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Yu, Haihua, Yi, Hong, Wang, Wei
• Primary Examiner(s): SHAH, UTPAL D
• Application Number:
  US13/666,152
• Publication Number:
  US 20130121601A1
• Time in Patent Office: 712 Days
• Field of Search: 382/294, 382/286, 382/287
• US Class Current: 382/294
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/10152 Varying illumination
• CPC Class Codes: G06T 2207/20164 Salient point detection; Corner detection
• CPC Class Codes: G06T 7/00 Image analysis
• CPC Class Codes: G06T 7/73 using feature-based methods

Abstract

A method and an apparatus for determining a projection area of an image are provided. The method for determining a projection area of an image, comprises: an input step of inputting an image sequence having a plurality of images; a detecting step of detecting locations of projection areas of the respective images in the image sequence; a relationship classification judging step of judging a relationship classification between the image and a previous image before the image being projected based on a relationship between the location of the projection area of the image and the location of the projection area of the previous image; and a determining step of determining the locations of the projection areas of the respective images based on the relationship classification judged in the relationship classification judging step.

Claims

1. A method for determining a projection area of an image, comprising:

an input step of inputting an image sequence having a plurality of images;

a detecting step of detecting locations of projection areas of the respective of images in the image sequence;

a relationship classification judging step of judging a relationship classification between an image being projected and a previous image before the image being projected based on a relationship between the location of the projection area of the image and the location of the projection area of the previous image; and

a determining step of determining the locations of the projection areas of the respective images based on the relationship classification judged in the relationship classification judging step.

2. The method for determining a projection area of an image according to claim 1, wherein

in the detecting step, the detected locations of four corner points of a quadrilateral of the projection area of the image represent the location of the projection area.

3. The method for determining a projection area of an image according to claim 2, wherein

in the relationship classification judging step, it is judged that the relationship classification between the image and the previous image is a first classification in cases where a variation of a ratio of border lengths between the projection area of the image and the projection area of the previous image is greater than, or equal to or greater than a ratio difference threshold, and

in the determining step, the location of the projection area of the previous image is determined as the location of the projection area of the image when the relationship classification between the image and the previous image is the first classification.

4. The method for determining a projection area of an image according to claim 2, wherein

in the relationship classification judging step, it is judged that the relationship classification between the image and the previous image is a second classification in cases where a variation of a ratio of border lengths between the projection area of the image and the projection area of the previous image is less than, or equal to or less than a ratio difference threshold and the number of the corner points for which the location of the corner point changes is greater than, or equal to or greater than a number threshold, and a variation of the locations of the corner points is greater than, or equal to or greater than a location difference threshold, and

in the determining step, the location of the projection area of the image detected in the detecting step is determined as the location of the projection area of the image when the relationship classification between the image and the previous image is the second classification.

5. The method for determining a projection area of an image according to claim 2, wherein

in the relationship classification judging step, it is judged that the relationship classification between the image and the previous image is a third classification in cases where a variation of the locations of the corner points is less than, or equal to or less than a location difference threshold, and

in the determining step, the location of the projection area of the previous image is determined as the location of the projection area of the image when the relationship classification between the image and the previous image is the third classification.

6. The method for determining a projection area of an image according to claim 1, wherein

in the relationship classification judging step, it is judged that the relationship classification between the image and the previous image is a fourth classification in cases where the detected projection area of the image does not constitute a quadrilateral or the projection area cannot be detected in the image in the detecting step;

and

in the determining step, the location of the projection area of the previous image is determined as the location of the projection area of the image when the relationship classification between the image and the previous image is the fourth classification.

7. The method for determining a projection area of an image according to claim 4, wherein

displacements of four corresponding corner points between the projection area of the image and the projection area of the previous image are respectively calculated, and the sum of the displacements of four corresponding corner points is regarded as the variation of the locations of the corner points.

8. The method for determining a projection area of an image according to claim 4, wherein

horizontal displacements and vertical displacements of four corresponding corner points between the projection area of the image and the projection area of the previous image are respectively calculated, and the variation of the locations of the corner points is obtained by calculating the weighted sum of the horizontal displacements and the vertical displacements.

9. The method for determining a projection area of an image according to claim 3, wherein

absolute values of differences of aspect ratios of two adjacent borders of corresponding corner points between the projection area of the image and the projection area of the previous image are respectively calculated, and the sum of the absolute values of the differences is regarded as the variation of the ratio of border lengths.

10. An apparatus for determining a projection area of an image, comprising:

an input unit for inputting an image sequence having a plurality of images;

a detecting unit for detecting locations of projection areas of the respective images in the image sequence;

a relationship classification judging unit for judging a relationship classification between an image being projected and a previous image before the image being projected based on a relationship between the location of the projection area of the image and the location of the projection area of the previous image; and

a determining unit for determining the locations of the projection areas of the respective images based on the relationship classification judged by the relationship classification judging unit.