dn2nbr (short for Digital Numbers to Normalized Burn Ratio) is a plugin designed to work in Qgis to calculate the NBR from a Landsat 7 image with Digital Numbers values. 
Obtaining a NBR image is a tedious task since bands 4 and 7 of the scene have to be converted to radiance and reflectance values (using gap masks if necessary) prior to calculating the NBR itself, so this script was created to simplify the process.

2 new images will be created from the inputs with the radiance and reflectance values, each output will have the same name of the input along with the "_RAD" and "_REF" suffix respectively. The final NBR image's name will be specified by the user.

This is a first working version where the following should be noticed:

-Gap masks are mandatory
-There are 2 types of MTL files, one where radiance levels appear as LMAX_BANDx and other where theyr're found as RADIANCE_MAXIMUM_BAND_x the plugin currently supports only the latter. Future versions will accept both types.