Visible Atmospherically Resistant Index (VARI)
"The Visible Atmospherically Resistant Index (VARI) is designed to emphasize vegetation in the visible portion of the spectrum, while mitigating illumination differences and atmospheric effects. It is ideal for RGB or color images; it utilizes all three color bands.
VARI = (Green - Red)/ (Green + Red - Blue)
Green = pixel values from the green band
Red= pixel values from the red band
Blue = pixel values from the blue band
Reference: Gitelson, A., et al. "Vegetation and Soil Lines in Visible Spectral Space: A Concept and Technique for Remote Estimation of Vegetation Fraction." International Journal of Remote Sensing 23 (2002): 2537−2562." (ESRI, 2018)