Method, apparatus, computer program, computer system, and computer-readable storage medium for representing and searching for an object in an image

1. A method of deriving a factor indicating the reliability for a descriptor representing an object appearing in an image or sequence of images, by processing signals corresponding to the image or images, the method comprising:

deriving a plurality of numerical values associated with features appearing on the outline of an object to form a descriptor of said outline;

deriving a factor indicating the reliability of said descriptor using a relationship between at least two of said values; and

storing the derived factor.

2. A method as claimed in claim 1 wherein the factor is based on the ratio between two of said values.

3. A method as claimed in claim 2 wherein the ratio is of the two greatest values.

4. A method as claimed in claim 1 wherein said values are values of a CSS curvature scale space representation.

5. A method as claimed in claim 4 wherein said values are peak height co-ordinate values.

6. A method as claimed in claim 1 wherein a curvature scale space representation of the outline is obtained by smoothing the outline in a plurality of stages using a smoothing parameter sigma, resulting in a plurality of outline curves, using values for the maxima and minima of the curvature of each outline curve to derive curves characteristic of the original outline, and selecting the co-ordinates of peaks of said characteristic curves as said numerical values.

7. A method as claimed in claim 1 further comprising applying a predetermined ordering to said numerical values to arrive at a representation of the outline.

8. A method as claimed in claim 7 wherein the predetermined ordering is such that the resulting representation is independent of the starting point on the outline.

9. A method as claimed in claim 7 wherein the values are ordered starting from the greatest value.

10. A method as claimed in claim 9 wherein the values are ordered in decreasing size.

11. A method as claimed in claim 7 wherein the values are ordered starting from the smallest value.

12. A method of searching for an object in an image or sequence of images, by processing signals corresponding to images, the method comprising

inputting a query in the form of a two-dimensional outline;

deriving a query descriptor of said outline;

deriving a factor for said query descriptor using a method as claimed in claim 1 ;

obtaining a descriptor of objects in stored images;

comparing said query descriptor with each descriptor for a stored object; and

selecting and displaying at least one result corresponding to an image containing an object for which the comparison indicates a degree of similarity between the query and said object.

13. A method as claimed in claim 12 wherein a factor is derived for each descriptor for a stored object by deriving a plurality of numerical values associated with features appearing on the outline of an object to form a descriptor outline; deriving a factor indicating the reliability of said descriptor using a relationship between at least two of said values; storing the derived factor ; and

wherein the comparison is made using a predetermined ordering only or the predetermined ordering and some other ordering depending on said factors.

14. An apparatus comprising:

an image database storing still and video images;

a descriptor database storing descriptors for objects or parts of objects appearing in the images stored in the image database; and

a processor configured to perform the method as claimed in claim 1 or claim 12 .

15. A computer-readable storage medium storing computer-executable process steps for implementing a method as claimed in claim 1 or claim 12 .

16. A computer system comprising:

an image database storing still and video images;

a descriptor database storing descriptors for objects or parts of objects appearing in the images stored in the image database; and

a control unit programmed to perform the method as claimed in claim 1 or claim 12 .