Image processing

• US 20020175921A1
• Filed: 05/10/2002
• Published: 11/28/2002
• Est. Priority Date: 12/10/1999
• Status: Active Grant

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Xu, Li-Qun, Izquierdo, Ebroul
• Granted Patent: US 7,050,646 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G06V 10/26 Segmentation of patterns in the image field; Cutting or merging of image elements to establish the pattern region, e.g. clustering-based techniques; Detection of occlusion
• CPC Class Codes: G06V 10/28 Quantising the image, e.g. histogram thresholding for discrimination between background and foreground patterns

Abstract

One aspect of the invention concerns a method and system for processing an image recorded by an imaging device. The method comprises the steps of:- a) providing an image comprising an array of adjacent elements each corresponding to a respective part of the image and having a respective intensity value associated therewith (400); b) processing the intensity values to determine an intensity contrast value for each respective element according to differences in intensity values between respective adjacent elements (402); c) determining a depth value for each element corresponding to the distance between the imaging device and at least part of an image forming object represented in the image by the respective element (404); d) processing the depth values to determine a depth contrast value for each respective element according to differences in depth values between respective adjacent elements (406); and, processing said intensity contrast values and said depth contrast values to identify at least one area of the image corresponding to one or more respective objects in the image being processed (408). Step (408) can be a non-linear diffusion process whereby variations in grey level values are diffused in regions corresponding to objects or background and enhanced in regions corresponding to object boundaries.

Claims

1. An method of processing an image recorded by an imaging device;

said method comprising the steps of;

a) providing an image comprising an array of adjacent elements each corresponding to a respective part of the image and having a respective intensity value associated therewith;

b) processing said intensity values to determine an intensity contrast value for each respective element according to differences in intensity values between respective adjacent elements;

c) providing a depth value for each element corresponding to the distance between the imaging device and at least part of an image forming object represented in the image by the respective element;

d) processing said depth values to determine a depth contrast value for each respective element according to differences in depth values between respective adjacent elements; and

,

e) processing said intensity contrast values and said depth contrast values to identify at least one area of the image corresponding to one or more respective objects in the image being processed.

2. A method according to claim 1 wherein said depth values are determined according to the spacing between corresponding points on a stereoscopic image pair.

3. A method according to claim 2 wherein the spacing between said points is determined by matching said corresponding points and estimating a vector value for the relative spacing and direction of said points.

4. A method according to any preceding claim wherein said area is determined by identifying an outline of said respective object or objects in the image.

5. A method according to any preceding claim wherein step e) comprises the step of altering the intensity values of each respective element in accordance with the respective intensity contrast value and the respective depth contrast value of the element.

6. A method according to claim 5 wherein the step of altering the intensity values comprises the step of modifying the respective intensity contrast values according to the respective depth contrast values, and altering the intensity values of the respective elements towards an average intensity value determined by intensity values of surrounding elements if the respective modified intensity contrast value of the element is below a threshold value.

7. A method according to claim 6 wherein the intensity contrast values are modified such that elements having a higher than average depth contrast value have their respective intensity values altered less than elements having a lower than average depth contrast value.

8. A method according to any preceding claim wherein step e) comprises a non-linear diffusion process for altering element intensity values in accordance with respective intensity contrast values modified in accordance with respective depth contrast values.

9. A method according to any one of claims 5 to 8 further comprising the step of de-lineating said object or objects from the image.

10. A method according to claim 9 wherein the delineating step comprises the steps of:

determining a distribution of the altered intensity values of the respective elements;

determining a threshold value or range of values to include all the intensity values of the respective elements of at least one identified area in the image; and

,

selecting elements having modified intensity values within the threshold range or above or below said threshold value; and

delineating image data relating to said selected elements from image data relating to the remaining elements.

14. A system configured to implement a method according to any preceding claim

11. An method of processing an image in accordance with a non-linear diffusion process;

said method comprising the steps of;

a) providing an image comprising an array of adjacent elements each orresponding to a respective part of the image and having a respective intensity value ssociated therewith;

b) processing said intensity values to determine an intensity contrast value for each respective element according to differences in intensity values between respective adjacent elements;

c) identifying from said array of elements object defining elements corresponding to points on respective objects in the image;

d) altering said element intensity values in accordance said respective intensity contrast values, whereby said elements are altered to a lesser or greater extent in dependence on whether said respective element is an object element.

12. A method according to claim 11 wherein step c) comprises the step of determining a depth value associated with a disparity field for each element in the image and identifying said object elements from said depth values.

13. A method according to claim 11 wherein step c) comprises the step of determining a motion value associated with a motion vector in a video sequence for each element in the image and identifying said object elements from said motion values.

15. An image processing system for processing an image recorded by an imaging device;

said system comprising;

a) a data receiver for receiving data relating to an image comprising an array of adjacent elements each corresponding to a respective part of the image and having a respective intensity value associated therewith;

an intensity value processor configured to determine an intensity contrast value for each respective element according to differences in intensity values between respective adjacent elements;

a depth value processor configured to determine a depth value for each element corresponding to the distance between the imaging device and at least part of an image forming object represented in the image by the respective element;

a depth contrast value processor configured to determine a depth contrast value for each respective element according to differences in depth values between respective adjacent elements; and

,

an object segment processor configured to process intensity contrast values and said depth contrast values to identify at least one area of the image corresponding to one or more respective objects in the image being processed.