Method and apparatus for correction of perspective distortion

• US 20050179688A1
• Filed: 06/28/2004
• Published: 08/18/2005
• Est. Priority Date: 02/17/2004
• Status: Active Grant

• Current Assignee: Corel Corporation (Corel Holdings LP)
• Original Assignee: Corel Corporation (Corel Holdings LP)
• Inventors: Zaklika, Krzysztof Antoni, Chernichenko, Dmitry Alexandrovich
• Granted Patent: US 7,239,331 B2
• Time in Patent Office: Days
• US Class Current: 345/427
• CPC Class Codes: G06T 2207/20104 Interactive definition of region of interest [ROI]
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: G06T 7/536 from perspective effects, e.g. by using vanishing points

Abstract

Perspective distortion in an imaged scene is corrected by identifying a group of points in the imaged scene such that the group of points define a shape. Two vanishing points are determined based on the group of points in the imaged scene. The process determines a first set of reference points within the shape defined by the group of points and transforms the first set of reference points into a second set of reference points. An aspect ratio associated with the first set of reference points is adjusted and the imaged scene is transformed to reduce perspective distortion in the imaged scene.

Claims

1. A method of correcting perspective distortion in an imaged scene, the method comprising:

identifying a plurality of points in the imaged scene, wherein the plurality of points define a shape;

determining two vanishing points based on the plurality of points;

determining a first set of reference points within the shape defined by the plurality of points;

transforming the first set of reference points into a second set of reference points;

adjusting an aspect ratio associated with the first set of reference points; and

transforming the imaged scene to reduce perspective distortion in the imaged scene.

2. The method of claim 1, wherein the plurality of points define a quadrilateral shape.

3. The method of claim 1, wherein the plurality of points define a geometric shape having at least three sides.

4. The method of claim 1, wherein each of the plurality of points has an associated X coordinate and an associated Y coordinate.

5. The method of claim 1, wherein the plurality of points are identified by a user and correspond to an object in the imaged scene.

6. The method of claim 1, wherein determining a vanishing point includes extending lines on opposite sides of the shape until the lines intersect one another.

7. The method of claim 1, wherein the plurality of points define a quadrilateral shape, and wherein determining two vanishing points includes extending pairs of lines on opposite sides of the quadrilateral shape until each pair of lines intersect one another.

8. The method of claim 1, wherein determining a first set of reference points includes selecting points that define a rectangle within the shape defined by the plurality of points in the imaged scene.

9. The method of claim 1, wherein transforming the first set of reference points into a second set of reference points includes applying a transformation matrix to the first set of reference points.

10. The method of claim 1, wherein adjusting an aspect ratio associated with the first set of reference points includes:

estimating an aspect ratio based on the second set of reference points; and

modifying the first set of reference points to have an aspect ratio common with the estimated aspect ratio.

11. The method of claim 1, further comprising rotating an image associated with the first set of reference points if lines from a center point of a shape defined by the first set of reference points to the two vanishing points do not pass through adjacent sides of the shape defined by the first set of reference points.

12. One or more computer-readable media having computer-readable instructions thereon which, when executed, implement the method of claim 1.

13. A computing system embodying the computer-readable media of claim 12.

14. A method of processing an image, the method comprising:

identifying a plurality of user-selected points in the image, wherein the plurality of user-selected points define a first shape contained in the image;

determining a first set of reference points that define a second shape contained within the first shape;

transforming the first set of reference points into a second set of reference points;

adjusting an aspect ratio associated with the first set of reference points to create an adjusted first set of reference points; and

modifying the image based on the adjusted first set of reference points and the second set of reference points.

15. The method of claim 14, wherein the first shape is a quadrilateral shape and the second shape is a quadrilateral shape.

16. The method of claim 14, wherein the first shape has at least three sides and the second shape has at least three sides.

17. The method of claim 14, wherein adjusting an aspect ratio associated with the first set of reference points includes:

estimating an aspect ratio based on the second set of reference points; and

modifying the first set of reference points to have an aspect ratio approximately the same as the estimated aspect ratio.

18. The method of claim 14, further comprising determining at least two vanishing points based on the plurality of user-selected points.

19. The method of claim 18, wherein the plurality of user-selected points define a shape having at least three sides, and wherein determining at least two vanishing points includes extending pairs of lines on opposite sides of the shape having at least three sides until each pair of lines intersect one another.

20. One or more computer-readable media having computer-readable instructions thereon which, when executed, implement the method of claim 14.

21. A computing system embodying the computer-readable media of claim 20.

22. One or more computer-readable media having stored thereon a computer program that, when executed by one or more processors, causes the one or more processors to:

identify a plurality of points in an image, wherein the plurality of points define a shape contained in the image;

determine at least one vanishing point associated with the shape defined by the plurality of points;

identify a first set of reference points associated with the image;

transform the first set of reference points into a second set of reference points; and

transform the image by mapping the second set of reference points onto the first set of reference points.

23. The computer-readable media of claim 22, wherein the shape identified by the plurality of points is a geometric shape having at least three sides.

24. The computer-readable media of claim 22, wherein the one or more processors further adjust an aspect ratio associated with the first set of reference points prior to transforming the image.

25. The computer-readable media of claim 22, wherein the transformed image has reduced perspective distortion.

26. The computer-readable media of claim 22, wherein the one or more processors further determine a second vanishing point associated with the shape defined by the plurality of points.

27. The computer-readable media of claim 22, wherein the at least one vanishing point is determined by extending lines on opposite sides of the shape defined by the plurality of points until the lines intersect one another at the vanishing point.

28. The computer-readable media of claim 22, wherein the first set of reference points define a second shape having at least three sides, wherein the second shape is contained within the shape defined by the plurality of points.

29. An apparatus comprising:

an image selection module to identify an image;

a reference point generator coupled to the image selection module, the reference point generator to generate a first set of reference points that define a shape within the image;

a reference point transformation module coupled to the reference point generator, the reference point transformation module to transform the first set of reference points into a second set of reference points;

an aspect ratio adjustment module coupled to the reference point transformation module, the aspect ratio adjustment module to adjust an aspect ratio associated with the first set of reference points; and

an image mapping module coupled to the aspect ratio adjustment module, the image mapping module to modify the image based on the adjusted first set of reference points and the second set of reference points.

30. The apparatus of claim 29, further comprising an aspect ratio estimator coupled to the aspect ratio adjustment module, the aspect ratio estimator to estimate an aspect ratio based on the second set of reference points.

31. The apparatus of claim 30, wherein the estimated aspect ratio is used by the aspect ratio adjustment module in modifying the image.

32. The apparatus of claim 29, wherein the first set of reference points define a quadrilateral shape within the image.

33. The apparatus of claim 29, wherein the first set of reference points define a first quadrilateral shape and the second set of reference points define a second quadrilateral shape.

34. The apparatus of claim 29, wherein the reference point generator is further to determine at least one vanishing point based on the first set of reference points.