Method for color transition detection

• US 20050024379A1
• Filed: 08/26/2004
• Published: 02/03/2005
• Est. Priority Date: 07/21/2000
• Status: Active Grant

• Current Assignee: Sony Interactive Entertainment Inc. (Sony Group Corp.)
• Original Assignee: Sony Computer Entertainment Incorporated (Sony Group Corp.)
• Inventors: Marks, Richard L.
• Granted Patent: US 7,113,193 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: A63F 2300/1012 involving biosensors worn by the player, e.g. for measuring heart beat, limb activity
• CPC Class Codes: A63F 2300/1093 using visible light
• CPC Class Codes: G06F 3/0304 Detection arrangements using opto-electronic means constructional details of pointing devices not related to the detection arrangement using opto-electronic means G06F3/033; optical digitisers G06F3/042
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06T 7/62 of area, perimeter, diameter or volume
• CPC Class Codes: G06T 7/66 of image moments or centre of gravity
• CPC Class Codes: G06T 7/73 using feature-based methods

Abstract

A hand-manipulated prop is picked-up via a single video camera, and the camera image is analyzed to isolate the part of the image pertaining to the object for mapping the position and orientation of the object into a three-dimensional space, wherein the three-dimensional description of the object is stored in memory and used for controlling action in a game program, such as rendering of a corresponding virtual object in a scene of a video display. Algorithms for deriving the three-dimensional descriptions for various props employ geometry processing, including area statistics, edge detection and/or color transition localization, to find the position and orientation of the prop from two-dimensional pixel data. Criteria are proposed for the selection of colors of stripes on the props which maximize separation in the two-dimensional chrominance color space, so that instead of detecting absolute colors, significant color transitions are detected. Thus, the need for calibration of the system dependent on lighting conditions which tend to affect apparent colors can be avoided.

Claims

1. A method for selecting colors to detect color transitions, comprising:

providing an object having at least two colors for which a color transition is to be detected, a first color of the at least two colors defined by a first chrominance coordinate in a color space and a second color of the at least two colors defined by a second chrominance coordinate in the color space;

projecting a line from each respective point defined by the first and second chrominance coordinates to a diameter having a given angle of orientation θ

on a color wheel defined by the color space, the lines being normal to the diameter;

calculating a distance D between respective points where the lines intersect the diameter; and

selecting for detection of color transitions only colors for which the calculated distance D exceeds a predetermined threshold.

2. The method of claim 1 wherein the first coordinate in the color space is (Cr₁, Cb₁).

3. The method of claim 1 wherein the second coordinate in the color space is (Cr₂, Cb₂).

4. The method of claim 1 further comprising detecting the at least two colors with a camera device.

5. The method of claim 1 wherein the color space comprises a two-dimensional color space.

6. The method of claim 1 wherein the distance D is calculated according to the equation D=[Cr₁·

cos θ

+Cb₁·

sin θ

]−

[Cr₂·

cos θ

+Cb₂·

sin θ

].

7. The method of claim 1 wherein the distance D is calculated according to the equation D=[(Δ

Cr)²+(Δ

Cb)²]^1/2.

8. The method of claim 1 wherein the at least two colors have a large separation in the color space.

9. The method of claim 1 further comprising selecting the diameter having the given angle of orientation θ

.

10. A method for identifying color pixels in a video image comprising:

tracking an object of interest against a background, wherein the object of interest has a first color and the background has a second color;

detecting the first and second color, wherein each color is represented as a respective color chrominance coordinate in a color wheel in a color space;

projecting a line from each respective point defined by the first and second chrominance coordinates to a diameter having a given angle of orientation θ

on the color wheel defined by the color space, the lines being normal to the diameter;

calculating a distance D between respective points where the lines intersect the diameter; and

identifying those pixels wherein the calculated distance D exceeds a predetermined threshold.

11. The method of claim 10 further comprising identifying the object of interest in the video image, the object being comprised of pixels.

12. The method of claim 10 further comprising selecting the diameter having the given angle of orientation θ

.

13. The method of claim 10 wherein the background is multi-colored.

14. The method of claim 10 wherein the background is non-static.

15. The method of claim 10 further comprising deriving a description of three-dimensional position of the object of interest wherein deriving the description is a result of identifying a pixel.

16. The method of claim 10 wherein the distance D is calculated according to the equation D=[Cr₁·

cos θ

+Cb₁·

sin θ

]−

[Cr₂·

cos θ

+Cb₂·

sin θ

].

17. A machine readable medium having embodied thereon a program being executable by a machine to perform a method comprising:

tracking an object of interest against a background, wherein the object of interest has a first color and the background has a second color;

detecting the first and second color, wherein each color is represented as a respective color chrominance coordinate in a color wheel in a color space;

projecting a line from each respective point defined by the first and second chrominance coordinates to a diameter having a given angle of orientation θ

on the color wheel defined by the color space, the lines being normal to the diameter;

calculating a distance D between respective points where the lines intersect the diameter; and

identifying those pixels wherein the calculated distance D exceeds a predetermined threshold.

18. The method of claim 17 wherein the method further comprises identifying the object of interest in the video image, the object being comprised of pixels.

19. The method of claim 17 wherein the method further comprises deriving a description of three-dimensional position of the object of interest wherein deriving the description is a result of identifying a pixel.

20. The method of claim 17 wherein the distance D is calculated according to the equation D=[Cr₁·

cos θ

+Cb₁·

sin θ

]−

[Cr₂·

cos θ

+Cb₂·

sin θ

].