US 6,574,363 B1 · Method for color detection in video images

Abstract

A method of identifying pixels of a given color in a field of YUV video manipulates color difference signals (R-Y, B-Y) corresponding to defining axes (U,V) of a color space to maximize the video signal in a region of interest of the space, and minimize the signal in all other regions. Additionally, the color difference signal corresponding to one axis may be rotated toward the other axis, or the entire color space may be rotated to bring the region of interest onto or near one of the axes. The signal gains and rotations may be carried out in the signal processing circuits (52) of a conventional color camera (50) so that only one comparator (90) is needed to detect the target color. After rotation and application of gain, the color difference signal defining the region of interest is compared with a threshold value to determine if a pixel is of the target color. A video camera may be mounted on an agricultural sprayer to detect green weeds on the brown soil, by identifying the green pixels in the image captured while the sprayer travels in the field. A spray material may be released upon the weed, once the weed is detected.

Claims10

Dependent claims

A method of processing a video signal to determine when a pixel belongs to a region of interest of a color space, the method comprising the steps of, for each pixel:

a) transforming the video signal into color difference signals corresponding to a set of defining axes of the color space;
b) minimizing signal gain for all color difference signals except for a color difference signal defining the region of interest;
c) establishing a threshold value representing the minimum magnitude that the color difference signal defining the region of interest must have when the pixel belongs to the region of interest of the color space;
and,
d) comparing the color difference signal defining the region of interest with the threshold value to determine if the pixel is in the region of interest of the color space, wherein said region of interest is green, said defining axes are a V axis and a U axis, wherein the V axis is defined as the red axis and the U axis is defined as the blue axis, and the color difference signal defining the region of interest is a negative V axis signal, and wherein the step of minimizing signal gain comprises minimizing the U axis signal and positive V axis signal.

2 more elements

Dependencies are inferred from the claim text.

Method for color detection in video images

Life of this patent

Method for color detection in video images

Life of this patent

Abstract

Claims10