Make internal mask an option ? about rio-cogeo HOT 1 CLOSED

Right now we have those two options to give info about the input dataset:

  --nodata INTEGER                Force mask creation from a given nodata
                                  value
  --alpha INTEGER                 Force mask creation from a given alpha band
                                  number

and by default we create an internal mask.

If we make mask creation optional there are plenty of scenario we should take care:

• input dataset has a nodata value (or user passes --nodata) :

  • rio-cogeo creates internal mask (--add-mask ?)
  • rio-cogeo creates an alpha band (--add-alpha ?)
  • rio-cogeo passes the nodata value to the output dataset (and add a warning for lossless compression) if none of the --add-mask or --add-alpha are passed

• input dataset has an alpha band (or user passes --alpha)

  • rio-cogeo creates internal mask (--add-mask ?)
  • rio-cogeo copy the alpha band to the output dataset (--add-alpha ?)

• input dataset has a mask

  • rio-cogeo creates internal mask (--add-mask ?)
  • rio-cogeo creates an alpha band (--add-alpha ?)

• input dataset has no mask, alpha, nodata (✨ )

  • rio-cogeo creates internal mask (--add-mask ?) but will be useless
  • rio-cogeo creates an alpha band (--add-alpha ?) but will be useless

Note:
we could also maybe rename --nodata to --src-nodata and --alpha to --src-nodata to avoid any ambiguity ?

cc @perrygeo @sgillies

from rio-cogeo.