[GRASS5] [bug #3011] (grass) d.mon CELL doesn't work

[Paul Kelly]

On Sun, 24 Jul 2005, Maciek Sieczka wrote:

> Because we are talking here about substituting the CELL driver 
> functionality. And as I understand it, CELL driver is for obtaining a 
> Grass layer out of the monitor content (not a particular layer, like 
> r.out.gdal, or a fragment of layer currently displayed, like r.out.tiff 
> -t) with a colortable stored.

The only thing I can think that would be useful for was before there were 
direct monitor output methods like the PNG driver, you could write the 
monitor to a GRASS raster layer and then use r.out.tiff or whatever to get 
it into an output file.

>
>> unlikely to be georeferenced correctly).
>
> Sure.
>
> So here all arguments for having CELL driver to Grass61:
> 1. d.out.png + r.in.gdal requires an intermediate file to duplicate the 
> CELL driver functionality

But I can't think of a reason why you would want a monitor image as a 
GRASS raster; rather I would put it that it is the CELL driver that 
requires two images to get to an output graphics file.

> 2. r.region is required to georeference the PNG image dump back after 
> r.in.gdal

LIkewise for the CELL driver directly; the output image is not 
georeferenced as Glynn said.

> 3. if the image dump was over 8 bit, r.composite is required to merge the 
> 3 layers output by r.in.gdal; moreover, using r.composite, it is unlikely 
> to obtain an exact copy of the original PNG image dump

Make the image dump in 8-bit colour then.

> 4. alltogether, even if possible to overcome all these problem, CELL 
> driver seems much easier in use - one operation instead of 3 or 4.

It makes it easy to convert a monitor image into a GRASS raster, but what 
use is it once you've got it there? I feel it is an historical 
anachronism.

[...]
>> [1] Or, preferably, r.in.png once I add it to 6.1; I've only just
>> realised it was missing.
>
> Why do we need r.in.png if r.in.gdal provides this functionality?

I suppose it is simpler and doesn't rely in having GDAL working properly; 
Glynn may be able to describe technical advantages it has over GDAL 
specifically for the PNG format?

Just thought I'd join in, because I actually used the CELL driver for 
something years ago and so understand how useless it is :)

Paul