envi 2

right click on file.dat -> view metadata -> edit -> add

right click on file.dat -> view quick stats -> select plots -> all histograms

right click on file.dat -> profile -> spectral

click measure button, set cursor position at go to field in tool bar

click at center of crosshair, click on target. change unit

histogram stretch

reference:

Getting Started with ENVI Tutorial (l3harrisgeospatial.com)