[GRASS-user] Raster Import

[Glynn Clements]

Hamish wrote:

> > > Can i remove unrectified former 3 seperate rgb files?
> > Yes, after r.composite you can remove them.
> 
> but note that you will lose information. the 3 bands will
> probably be stored with 256 bit precision,

That's 256 levels = 8 bits per component, 24 bits total.

> r.composite will reduce fidelity down to probably 32 bit.

That's 32 levels = 5 bits per component, 15 bits total.

r.composite can generate ouput with 256 levels (8 bits per component,
24 bits total), but the resulting colour tables are large, which
creates a significant performance issue for any operation which needs
to perform colour lookup (e.g. d.rast).

> If you are doing any numerical analysis on satellite images, etc,
> this matters a lot and it's best to work with the raw bands, d.rgb,
> etc. If you are just using it for visual use maybe it doesn't
> matter.

Indeed.

-- 
Glynn Clements <glynn at gclements.plus.com>