img2mercgrd(1gmt) on Linux
The text 1a82b6c85666, as Debian 8 (Jessie) shipped it. The page shows this text now.
Extract region of img, preserving Mercator, save as grd
Flags it lists
-
-C -
-D -
-G -
-N -
-R -
-S -
-T -
-V -
-W -
-m