[GRASSLIST:5062] Re: ps.map and PNG driver comparison

[Hamish]

> Why do raster layers printed with ps.map look more
> coarse (lower resolution) than ones printed with PNG
> driver?


The number of raster cells used in a ps.map map is exactly the same as
the number defined by rows and columns in the g.region settings.
Make sure you have the resolution correct before creating the map.

The number of cells used by the PNG driver will be resampled to fit in
the monitor height and width, after the region resolution resampling.

So theoretically the ps.map output should generally be higher resolution
than the PNG output.. usually you can lower the region's resolution
before running ps.map and still get high quality output from a much
smaller file. Otherwise you get 40mb postscript files...

But a printed page will have finer detail than your monitor. Standard
PostScript/PDF is 72 dpi but a fine raster might print at 300 dpi.
Your monitor (PNG driver output) will generally by only ca. 800 pixels
wide, ie the same as a 2.7 inch printed version. Expand that to a full
printed page and you apparenlty lower resolution ??



Hamish