Method and apparatus for evaluating a scale factor and a rotation angle in image processing

• US 6,549,683 B1
• Filed: 05/02/2000
• Issued: 04/15/2003
• Est. Priority Date: 05/02/2000
• Status: Expired due to Term

• Current Assignee: Institut national d'optique
• Original Assignee: Institut national d'optique
• Inventors: Doucet, Michel, Prevost, Donald, Bergeron, Alain
• Primary Examiner(s): Tran, Phuoc
• Application Number:
  US09/563,635
• Time in Patent Office: 1,078 Days
• Field of Search: 382/209, 382/210, 382/217, 382/218, 382/280, 382/278, 382/296, 382/297, 382/298, 708/403
• US Class Current: 382/298
• CPC Class Codes: G06T 7/66 of image moments or centre of gravity
• CPC Class Codes: G06T 7/74 involving reference images or patches
• CPC Class Codes: G06V 10/89 using frequency domain filters, e.g. Fourier masks implemented on spatial light modulators

Abstract

The present invention concerns a method for evaluating a scale factor and a rotation angle in image processing and more particularly digital image processing. The method includes the steps of first providing an input image, and then reducing the input image to provide a smaller image. The smaller image is scaled according to a plurality of factors to produce a plurality of scaled images and is also rotated according to a plurality of factors to produce a plurality of rotated images. The scaled images in the rotated images are then placed into a mosaic which is arranged by scale and rotation. A referenced template is provided and the referenced template is correlated with the mosaic of scaled and rotated images to provide a scale factor and a rotation angle based on the position in the mosaic of the high score relation value between the reference template and the scaled and rotated images. The method is more efficient in that it reduces the amount of computations required to obtain useful results. The method also does not require object centering prior to performing the analysis and does not require complex mathematical expansion of the object under analysis.

Claims

1. A method for evaluating a scale factor and a rotation angle in image processing, comprising the steps of:

(a) providing an input image;

(b) reducing the input image to provide a smaller image;

(c) scaling the smaller image according to a plurality of factors to produce a plurality of scaled images;

(d) rotating the smaller image according to a plurality of factors to produce a plurality of rotated images;

(e) placing the scaled images and the rotated images into a mosaic arranged by scale and rotation;

(f) providing a reference template;

(g) correlating said reference template with said mosaic of scaled and rotated images; and

(h) providing a scale factor and a rotation angle based on the position in the mosaic of the highest correlation value between the reference template and the scaled and rotated images.

2. A method according to claim 1, wherein said method further includes step (f.1) performing a Fourier transform on said reference template.

3. A method according to claim 1, wherein said step (c) of scaling the reduced images comprises an isomorphic scale change.

4. A method according to claim 1, wherein said step (c) of scaling the reduced image comprises an anamorphic scale change.

5. A method according to claim 1, wherein said rotation is an in-plane rotation.

6. A method according to claim 1, wherein said rotation is an out-of-plane rotation.

7. A method according to claim 1, further comprising the steps of:

(i) remapping the input image to its input size; and

(j) comparing the remapped image to a reference template at a higher resolution for recognising the input image.

8. A method according to claim 1, wherein said step (j) includes correlating the remapped image to a reference template.

16. A method according to claim 1, wherein said step (j) includes correlating the remapped image to a reference template.

9. A method for evaluating a scale factor and a rotation angle in image processing, comprising the steps of:

(a) providing an input image;

(b) reducing the input image to provide a smaller image;

(c) providing a reference template;

(d) scaling the reference template according to a plurality of factors to produce a plurality of scaled images;

(e) rotating the reference template according to a plurality of factors to produce a plurality of rotated images;

(f) placing the scaled images and the rotated images into a mosaic arranged by scale and rotation;

(g) correlating said smaller image with said mosaic of scaled and rotated images; and

(h) providing a scale factor and a rotation angle based on the position in the mosaic of the highest correlation value between the smaller image and the scaled and rotated images.

10. A method according to claim 9, wherein said method further includes step (b.1) performing a Fourier transform on said smaller image.

11. A method according to claim 9, wherein said step (d) of scaling the reference template comprises an isomorphic scale change.

12. A method according to claim 9, wherein said step (d) of scaling the reference template comprises an anamorphic scale change.

13. A method according to claim 9, wherein said rotation is an in-plane rotation.

14. A method according to claim 9, wherein said rotation is an out-of-plane rotation.

15. A method according to claim 9, further comprising the steps of:

(i) remapping the input image to its input size; and

(j) comparing the remapped image to a reference template at a higher resolution for recognising the input image.

17. A system for evaluating a scale factor and a rotation angle in image processing, comprising:

(a) input means for receiving an input image;

(b) means for reducing the input image to provide a smaller image;

(c) means for scaling the smaller image according to a plurality of factors to produce a plurality of scaled images;

(d) means for rotating the smaller image according to a plurality of factors to produce a plurality of rotated images;

(e) means for receiving and placing the scaled images and the rotated images into a mosaic arranged by scale and rotation;

(f) means for providing at least one reference template;

(g) means for correlating each of said at least one reference template with said mosaic of scaled and rotated images; and

(h) means for providing a scale factor and a rotation angle based on the position in the mosaic of the highest correlation value between each of the reference templates and the scaled and rotated images.

18. A system for evaluating a scale factor and a rotation angle in image processing, comprising:

(a) input means for receiving an input image;

(b) means for reducing the input image to provide a smaller image;

(c) means for providing at least one reference template;

(d) means for scaling each of the at least one reference template according to a plurality of factors to produce a plurality of scaled images;

(e) means for rotating each of the at least one reference template according to a plurality of factors to produce a plurality of rotated images;

(f) means for placing the scaled images and the rotated images into a mosaic arranged by scale and rotation for each of the reference template;

(g) means for correlating said smaller image with each of said mosaic of scaled and rotated images; and

(h) means for providing a scale factor and a rotation angle based on the position in the mosaic of the highest correlation value between the smaller image and the scaled and rotated images.

19. A method for evaluating a scale factor and a rotation angle in image processing, comprising the steps of:

(a) providing an input image;

(b) scaling the image according to a plurality of factors to produce a plurality of scaled images;

(c) rotating the image according to a plurality of factors to produce a plurality of rotated images;

(d) placing the scaled images and the rotated images into a mosaic arranged by scale and rotation;

(e) providing a reference template;

(f) correlating said reference template with said mosaic of scaled and rotated images; and

(g) providing a scale factor and a rotation angle based on the position in the mosaic of the highest correlation value between the reference template and the scaled and rotated images.