Claims
- 1. A method in image processing for detection of a change in a scene in an area, comprising the steps of
recording a digital image of the area using a sensor, transforming the recorded image by an operator that is based on a previous modeling of changes in the lighting in the area and on a modeling of how the sensor depicts the area in grayscale values in the recorded image, and comparing the transformed image with a reference image of the area in order to detect a difference that indicates a change in the scene.
- 2. A method according to claim 1, in which the reference image is transformed by said operator.
- 3. A method according to claim 1, in which the operator is invariant with regard to transformations of said grayscale values in the recorded image.
- 4. A method according to claim 1, in which the operator is an affine invariant.
- 5. A method according to claim 4, in which the step of transforming comprises the steps of filtering the recorded image with a first filter, filtering the recorded image with a second filter, the first and the second filter differing from each other and both having the coefficient sum zero, and determining the quotient between the filtered images.
- 6. A method according to claim 5, in which the first and the second filter are a derivative of the Gaussian function.
- 7. A method according to claim 6, in which the first filter is a derivative of the Gaussian function in the x-direction and the second filter is a derivative of the same Gaussian function in the y-direction.
- 8. A method according to claim 5, in which the first and the second filter are two simple difference filters between the grayscale value in one pixel and the grayscale value in another pixel.
- 9. A method according to claim 8, in which the first filter is a difference filter between two pixels horizontally adjacent to each other and the second filter is a difference filter between two pixels vertically adjacent to each other.
- 10. A method according to claim 1, in which the operator is a modification of normalized vector distance, the step of transforming comprising the steps of calculating the mean value of the grayscale value in a subset of the recorded image, subtracting the mean value in each pixel, and carrying out a normalized vector distance calculation.
- 11. A method according to claim 10, in which the step of comparing comprises the step of calculating the difference between respective vectors in the transformed recorded image and the transformed reference image.
- 12. A method according to claim 1, further comprising the step of adapting at least two parameters to the operator.
- 13. A method according to claim 12, in which said parameters are adapted in such a way that they cover all transformations of said grayscale values.
- 14. A method according to claim 13, in which the operator is an affine transformation.
- 15. A method according to claims 12, in which the step of adapting said parameters to the operator is carried out locally in the recorded image.
- 16. A method according to claim 1, further comprising the step of filtering both the recorded image and the reference image with a smoothing filter.
- 17. A method according to claim 16, in which the smoothing filter is a Gaussian function.
- 18. A computer program that is stored on a computer-readable memory medium that comprises instructions for causing a computer to carry out the method according to any one of claims 1-17.
- 19. Use of an operator in image processing for the detection of a change in the scene in an image of an area recorded by a sensor, which operator is based on a previous modeling of changes in the lighting in the area and on a modeling of how the sensor depicts the area in grayscale values in the recorded image.
- 20. Use according to claim 19, in which the operator is invariant with regard to the transformations of the grayscale values that arise as a result of the changes in the lighting in the area and as a result of how the sensor depicts these changes in the lighting in grayscale values in the digital image.
- 21. Use according to claim 20, in which the operator is an affine invariant.
- 22. A system for monitoring an area, comprising at least one sensor for recording images of the area, a memory in which the computer program according to claim 18 is stored and a processing unit.
- 23. Use of a method according to any one of claims 1-17 for controlling an automatic door-opener.
Priority Claims (1)
Number |
Date |
Country |
Kind |
0102209-4 |
Jun 2001 |
SE |
|
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related to, and claims the benefit of, a previously filed U.S. Provisional Pat. Application, titled “Adjusted Filters,” application No. 60/301,946, filed Jun. 29, 2001.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60301946 |
Jun 2001 |
US |