[GRASSLIST:8398] Re: ps.map resolution

[Glynn Clements]

Ian MacMillan wrote:

> Hi all, I don't think this has been discussed on the mailing list 
> before, sorry if it has.  Is there any way to increase the resolution 
> of a raster using ps.map?
> 
>   As near as I can tell, all rasters come out at 72 dpi.  My work-around 
> so far has been to use ps.map, then double, triple, or quadruple my 
> scale on a huge page, then use some other software to scale that back 
> down to increase the resolution of the raster within the postscript 
> file.  This gets cumbersome for large maps.
> 
> One used to be able to mess around in $GISBASE/etc/paint/ps.devices so 
> that you could add or delete different paper sizes with their 
> resolutions I believe, but that is no longer an option it seems with 
> ps.map.  Looking at the paper.h file of the source, it seems that the 
> preset page sizes do not have a resolution option either.

PostScript files are rendered at the resolution of the output device. 
For a printer, this will typically be between 300 and 1200 dpi; for a
monitor it's usually between 75 and 120 dpi. If you render to an image
file with Ghostscript, it will use whatver resolution you tell it to
via the -r switch (IIRC, the default is 75 dpi).

The raster which is embedded in the PostScript file will be generated
using the region settings, so if your current region has a lower
resolution than the raster itself, the resolution will be reduced.

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