The ExG operator algorithm computes the Excess Green Index from a given product.

The ExG results from the following equation:

ExG = 2 * G - R - B

, where:

The bands are:

- B is the Blue band
- G is the Green band
- R is the Red band

Also the processor computes an additional flags band called 'exg_flags' with the following bit coding:

Bit Position	Description
Bit 0	The computed value for ExG is NAN or is Infinite
Bit 1	The computed value for ExG is less than -1 (minus one)
Bit 2	The computed value for ExG is greater than 1 (one)