COLOR INDEXES FOR WEED IDENTIFICATION UNDER VARIOUS SOIL, RESIDUE, AND LIGHTING CONDITIONS

Color slide images of weeds among various soils and residues were digi tized and analyzed for red, green, and blue (RGB) color content. Red, green, and blue chromatic coordinates (rgb) of plants were very differ ent from those of background soils and residue. To distinguish living plant material from a nonplant background, several indices of chromati c coordinates were studied, rested, and were successful in identifying weeds. The indices included r-g, g-b, (g-b)/\r-g\, and 2g-r-b. A modi fied hue was also used to distinguish weeds from non-plant surfaces. T he modified hue, 2g-r-b index, and the green chromatic coordinate dist inguished weeds from a nonplant background (0.05 level of significance ) better than other indices. However, the modified hue was the most co mputationally intense. These indices worked well for both nonshaded an d shaded sunlit conditions. These indices could be used for sensor des ign for detecting weeds for spot spraying control.