Method and system for determining and correcting image orientation angle
AssigneeLockheed Martin Corporation
InventorsLawrence E. Albertelli, David L. Ii, Nina Kung
Life of this patent
Estimating the term…
Abstract
A simple and robust method for determining the orientation angle of a scanned image or the angular orientation of an object in an electronic image based on using descriptors of the image and systems that implement the method are disclosed. A system including means for acquiring the electronic image, means for determining image centroid coordinates, means for obtaining second order moments corresponding to the image, and, means for determining an orientation angle of a principal axis of the image implements the method.
Claims10
A method of detecting an orientation angle of an image, said method comprising the steps of:
- determining image centroid coordinates;
- obtaining second order moments corresponding to the image and to the image centroid coordinates;
- and,
- determining an orientation angle of a principal axis of the image;
- obtaining the orientation angle of the image from the orientation angle of the principal axis;
- and
- rotating the image by an angle equal to the orientation angle of the image and in a direction that yields a rotated image with a substantially null orientation angle of the image after rotation;
- whereby said method is readily implemented with reduced computational complexity and the rotation of the image corrects the orientation of the image.
A system for detecting an orientation angle of an image, said system comprising:
- means for acquiring the image;
- means for determining image centroid coordinates;
- means for obtaining second order moments corresponding to the image, said second order moments utilizing the image centroid coordinates;
- means for determining an orientation angle of a principal axis of the image, wherein the orientation angle of the image is given by the orientation angle of the principal axis;
- and
- means for rotating the image;
- whereby the rotation corrects the orientation of the image.
A computer usable medium having computer readable code embodied therein for detecting an orientation angle of an image, said code causing a computer system to:
- determine image centroid coordinates;
- obtain second order moments corresponding to the image, said second order moments utilizing the image centroid coordinates;
- and,
- determine an orientation angle of a principal axis of the image, wherein the orientation angle of the image is given by the orientation angle of the principal axis;
- and
- rotate the image by an angle equal to the orientation angle of the image and in a direction that yields a rotated image with a substantially null orientation angle.
A method of detecting an orientation angle of an address block on an addressed item, said method comprising the steps of:
- acquiring an image of the addressed item;
- locating an address block image in the image of the addressed item;
- determining address block image centroid coordinates;
- obtaining second order moments corresponding to the address block image and to the address block image centroid coordinates;
- and,
- determining an orientation angle of a principal axis of the address block image;
- obtaining the orientation angle of the address block from the orientation angle of the principal axis;
- and
- rotating the image of the addressed item by an angle equal to the orientation angle of the address block and in a direction that yields a rotated image with a substantially null orientation angle of the address block after rotation;
- whereby said method is readily implemented with reduced computational complexity and whereby the rotation of the addressed item image corrects the orientation of the address block.
A method of detecting an orientation angle of an address block on an addressed item, said method comprising the steps of:
- acquiring an image of the addressed item;
- locating an address block image in the image of the addressed item;
- representing the address block image as an n-by-in two dimensional array of discrete image values, f(xi,yj), where i is selected from the group consisting of 1 through n, and, j is selected from the group consisting of 1 through m, and, xi, yj represent position coordinate values for the image value f(xi,yj);
- obtaining zeroth order moments, m00,m01,m10, from the equations
- m
- 00
- =
- ∑
- i
- =
- 1
- i
- =
- n
-
-
- ∑
- j
- =
- 1
- j
- =
- m
-
-
- f
-
- (
- x
- i
- ,
- y
- j
- )
- ,
-
- m
- 10
- =
- ∑
- i
- =
- 1
- i
- =
- n
-
-
- ∑
- j
- =
- 1
- j
- =
- m
-
-
- x
- i
-
- f
-
- (
- x
- i
- ,
- y
- j
- )
- ,
-
- m
- 01
- =
- ∑
- i
- =
- 1
- i
- =
- n
-
-
- ∑
- j
- =
- 1
- j
- =
- m
-
-
- y
- j
-
- f
-
- (
- x
- i
- ,
- y
- j
- )
- ;
- determining image centroid coordinates, x0,y0, from the equations
- x
- 0
- =
- m
- 10
- m
- 00
- ,
-
- y
- 0
- =
- m
- 01
- m
- 00
- ;
- obtaining second order moments, μ11,μ20 and μ02, corresponding to the image from the equation
- μ
- pq
- =
- ∑
- i
- =
- 1
- i
- =
- n
-
- ∑
- j
- =
- 1
- j
- =
- n
-
- (
- x
- i
- -
- x
- 0
- )
- p
-
- (
- y
- j
- -
- y
- 0
- )
- q
-
- f
-
- (
- x
- i
- ,
- y
- j
- )
- ,
- where p and q are selected from the group consisting of 0, 1, and 2;
- determining an orientation angle, θ, of a principal axis of the image from the equation
- θ
- =
- 1
- 2
-
- tan
- -
- 1
-
- (
- 2
-
-
- μ
- 11
- μ
- 20
- -
- μ
- 02
- )
- ;
- obtaining the orientation angle of the address block from the orientation angle of the principal axis;
- and
- rotating the image of the addressed item by an angle equal to the orientation angle of the address block and in a direction that yields a rotated image with a substantially null orientation angle of the address block after rotation;
- whereby said method is readily implemented with reduced computational complexity and whereby the rotation of the addressed item image corrects the orientation of the address block.
Dependencies are inferred from the claim text.