Method, apparatus, computer program, computer system, and computer-readable storage medium for representing and searching for an object in an image
A method of representing an object appearing in a still or video image, by processing signals corresponding to the image, comprises deriving a plurality of numerical values associated with features appearing on the outline of an object starting from an arbitrary point on the outline and applying a predetermined ordering to said values to arrive at a representative of the outline.
1. A method of representing an object appearing in an image or a sequence of images, by processing signals corresponding to the image or images, the method comprising:
deriving a curvature scale space (CSS) representation of an outline of an object starting from an arbitrary point on the outline, by smoothing the outline in a plurality of stages using a smoothing parameter, resulting in a plurality of outline curves;
using values for points of inflection of each outline curve to derive characteristic curves which are characteristic of the original outline;
selecting first co-ordinates of peaks of said characteristic curves, which correspond to the smoothing parameter, and corresponding second co-ordinate values representing the positions on the outline corresponding to the peaks; and
shifting one of the second co-ordinate values to zero, and shifting all the remaining second co-ordinate values corresponding to said peaks by an amount equivalent to the original co-ordinate value of the second co-ordinate value shifted to zero.
2. A method as claimed in claim 1 wherein the second co-ordinate values are cyclic within a predetermined range.
3. A method as claimed in claim 2 wherein the second co-ordinate values represent normalised distance or arc-length along the contour.
4. A method as claimed in claim 1 wherein the second co-ordinate values represent distance or arc-length along the contour.
5. A method as claimed in claim 1 comprising ordering on the basis of the first co-ordinate values before shifting on the basis of the second co-ordinate values.
6. A method as claimed in claim 5 wherein the first values are ordered starting from the greatest value.
7. A method as claimed in claim 5 wherein the first values are ordered in decreasing size.
8. 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 using a method as claimed in claim 1 ;
obtaining a descriptor of objects in stored images derived using a method as claimed in claim 1 ;
comparing said query descriptor with each obtained 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.
9. An apparatus comprising:
an image database storing still or video images;
a descriptor database storing descriptor of objects or parts of objects appearing the images stored in the image database; and
a processor configured to perform the method as claimed in claim 1 or claim 8 .
10. A computer-readable storage medium storing computer-executable process steps for implementing a method as claimed in claim 1 or claim 8 .
11. A computer system comprising:
an image database storing still or video images;
a descriptor database storing descriptors of 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 8 .