The ExGR operator algorithm computes the ExG - ExR Vegetation Index from a given product.

The ExGR results from the following equation:

ExGR = (2.0 * G - R - B) - (1.3 * R - G)

, 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 'exgr_flags' with the following bit coding:

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