Detection of environmental conditions in a sequence of images

• US 20070280504A1
• Filed: 05/30/2006
• Published: 12/06/2007
• Est. Priority Date: 05/30/2006
• Status: Active Grant

• Current Assignee: Intelliview Technologies Inc.
• Original Assignee: Intelliview Technologies Inc.
• Inventors: Cai, Jun, Badawy, Wael, Shehata, Mohammed, Radmanesh, Ahmad, Pervez, Muzamil Shah, Burr, Tyson
• Granted Patent: US 8,045,761 B2
• Time in Patent Office: Days
• US Class Current: 382/104
• CPC Class Codes: G06T 2207/30236 Traffic on road, railway or crossing
• CPC Class Codes: G06T 7/254 involving subtraction of images
• CPC Class Codes: G06T 7/90 Determination of colour characteristics
• CPC Class Codes: G06V 20/40 in video content extracting overlay text G06V20/62; video retrieval G06F16/70; processing of video elementary streams in video servers H04N21/234; processing of video elementary streams in video clients H04N21/44

Abstract

A method for determining the presence and location of static shadows and other ambient conditions (such as glare, snow, rain, etc.) in a series of time-successive images is provided. Each image comprises a series of image elements locatable on a plane, with each element being associated with a color defined by three chromatic elements. Furthermore, each image is partitioned into a set of elements, with each element comprising one or more pixels. According to the process of the present method, the ambient conditions are detected using a mixture of processes which utilize the chromatic elements, luminance qualities and temporal characteristics of the series of images.

Claims

1. A method for shadow detection in a series of image frames, the method comprising repeating the following steps:

acquiring a reference frame containing data elements and a current frame of data elements;

comparing corresponding elements of the current frame and the reference frame; and

using the comparison of corresponding elements of the current frame and the reference frame to create a static shadow map indicating which elements of the current frame correspond to shadows of objects not appearing in the frame.

2. The method of claim 1 in which comparing corresponding elements comprises eliminating from comparison elements that correspond to motion.

3. The method of claim 2 in which comparing corresponding elements further comprises creating an initial set of elements which are candidates for being shadows.

4. The method of claim 1 in which the reference frame is generated by a series of successive frames that contain no shadows.

5. The method of claim 4 in which the reference frame is generated immediately after sunrise.

6. The method of claim 1 in which comparing corresponding elements comprises:

computing a difference between the current frame and the reference frame; and

determining if the difference lies between two thresholds.

7. The method of claim 4 further comprising generating the reference frame by averaging a number of frames.

8. The method of claim 1 in which each data point of the reference frame and each data point of the current frame has color components.

9. The method of claim 2 further comprising filtering by determining elements that do not correspond to shadows.

10. The method of claim 1 carried out as part of a method of video surveillance.

11. The method of claim 10 in which the method of video surveillance is video surveillance of a roadway.

12. A computer readable material having programmable code which implements the method of claim 1.

13. The method of claim 1 in which comparing corresponding elements of the current frame and the reference frame is not performed when the current frame corresponds to a time after sunset and prior to sunrise.

14. A method for detecting weather features in a series of image frames, the method comprising repeating the following steps:

acquiring a current frame of data elements;

acquiring a sample frame corresponding to known weather features;

comparing corresponding elements of the current frame and the sample frame; and

using the comparison of corresponding elements of the current frame and the sample frame to create a weather features map indicating elements of the current frame corresponding to weather features.

15. The method of claim 14 in which comparing corresponding elements comprises eliminating from comparison elements that correspond to glare.

16. The method of claim 15 further comprising eliminating from comparison elements which are in close proximity to elements that correspond to glare.

17. The method of claim 14 in which comparing corresponding elements comprises eliminating from comparison elements that correspond to motion.

18. The method of claim 14 in which detecting weather features comprises detecting moving snow.

19. The method of claim 14 in which detecting weather features comprises detecting rain collecting on a video camera.

20. The method of claim 14 carried out as part of a method of video surveillance.

21. The method of claim 20 in which the method of video surveillance is video surveillance of a roadway.

22. The method of claim 14 in which the sample data is chosen according to the time of day and local sunrise and sunset times.

23. A computer readable material having programmable code which implements the method of claim 14.

24. A method for glare detection in a series of image frames, the method comprising the following steps:

acquiring a current frame of data elements and a reference frame of data elements;

comparing corresponding elements of the current frame and the reference frame; and

using the comparison of corresponding elements of the current frame and the reference frame to create a static glare map indicating which elements of the current frame correspond to glare.

25. The method of claims 24 in which comparing corresponding elements comprises eliminating from comparison elements that correspond to motion.

26. The method of claim 24 in which comparing corresponding elements of the current frame and the reference frame comprises determining if the luminance of an element location is over a threshold.

27. The method of claim 24 carried out as part of a method of video surveillance.

28. The method of claim 27 in which the method of video surveillance is video surveillance of a roadway.

29. A computer readable material having programmable code which implements the method of claim 24.