[Feature request] NBITS option for COG

[arkanoid87]

The current COG driver does not support NBITS option, which is available in GTIFF driver.

with COG:

gdal_translate -of byte -of COG -co NBITS=1 input.tif output_1bpp.tif
Warning 6: driver COG does not support creation option NBITS
# option ignored                                                                                                                                               

With GTIFF:

gdal_translate -of byte -of gtiff -co NBITS=1 input.tif output_1bpp.tif
# success                                                                                                                                                     

To get the equivalent of a COG with NBITS < 8 with GEOTIFF, it would be required to manually add all the settings collected into aosOptions variable here as creation options of a GTIFF file

gdal/frmts/gtiff/cogdriver.cpp

Line 1217 in 9c0d353

poGTiffDrv->CreateCopy(pszFilename, poCurDS, false, aosOptions.List(),

But the contents of the variable is not dumped in debug log

Having a COG with smaller-than-byte NBITS is useful to get faster I/O using less CPU, and possibly also smaller files depending on compression strategy.

[arkanoid87]

thanks!