Hello!
Why do raster layers printed with ps.map look more
coarse (lower resolution) than ones printed with PNG
driver?
Thanks in advance
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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
--- Hamish <hamish_nospam@yahoo.com> wrote:
> 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.
I did that.
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.
I set the environment variables GRASS_WIDTH and
GRASS_HEIGHT to match the g.region -p output, so the
PNG file should have exactly the same number of rows
and columns as ps.map output. But even printed to
paper (same size) the maps in detail look different.
The postscript file looks more "edgy" while the png
file looks smoother. I tried to print some
topographical maps with generaly rasterized line data.
Thanks for the reply, Miha Staut
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
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> 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.I set the environment variables GRASS_WIDTH and
GRASS_HEIGHT to match the g.region -p output, so the
PNG file should have exactly the same number of rows
and columns as ps.map output. But even printed to
paper (same size) the maps in detail look different.
The postscript file looks more "edgy" while the png
file looks smoother. I tried to print some
topographical maps with generaly rasterized line data.
what program are you using to print out the PNG file? It is likely that
is doing some smoothing (GIMP print filters, etc.) ?
Is it better detail or just soothness?
Hamish
--- Hamish <hamish_nospam@yahoo.com> wrote:
> > 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.
>
> I set the environment variables GRASS_WIDTH and
> GRASS_HEIGHT to match the g.region -p output, so
the
> PNG file should have exactly the same number of
rows
> and columns as ps.map output. But even printed to
> paper (same size) the maps in detail look
different.
> The postscript file looks more "edgy" while the
png
> file looks smoother. I tried to print some
> topographical maps with generaly rasterized line
data.what program are you using to print out the PNG
file? It is likely that
is doing some smoothing (GIMP print filters, etc.) ?Is it better detail or just soothness?
Hamish
I think just smoothness (printed with Photoshop 5.0).
I know that this does not regard GRASS necesarily but
also the ps2pdf command when displayed and printed
produced a kind of "preview". I will try to send you
an example but currently I can not as I am not at my
computer now.
Thanks, Miha Staut
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