Usage: img2tif [-i img_filename] [-o tif_basename] [-c] 
               [-rgb [red green blue]] [-v  n...] [-?] [-quiet]

Arguments:
    -i    <input .img file>
    -o    <output base file name>
          Output files will be named base_name1.tif ... base_nameN.tif,
          where N = no. of bands.
    -rgb  produce an RGB image file from the indicated red, green and blue
          bands.
    -c    [packbits compress flag (def=uncompressed)]
    -v    [overview sampling increment(s) (0=single, 98=full set minus 2x,
           99=full set, def=98)  Examples: -v 2 4 8   -v 0   -v 99]
    -quiet Don't produce a translation report.
    -?    Print explanation of command line arguments

Other notes:
 o If the -rgb switch isn't given then a greyscale, or pseudocolored TIFF
   file will be generated for each band in the source file.

 o If the source file has no image bands an error message will be produced
   and execution stopped. 

 o The translation report (on by default) would indicate the source
   projection, total number of bands and their types, and any other meta
   information I judge to be potentially useful.

 o As discussed, I will extract the image pyramids and write them to the
   GeoTIFF file if they are available.  If the -v flag is given existing
   pyramids will be ignored, and new ones generated on the fly.

 o The output file would always be tiled, with the same tiling arrangement
   as the source Imagine file.

 o The .img Descriptor_Table.Statistics.minimum, and maximum fields will be
   used to set the MinSampleValue, and MaxSampleValue fields in the TIFF file
   if they are available.