Ok,
the discussion about DPI and rescaling did not exacly go well...
Jody suggested that my second attempt on GeoServer mailing list
(which basically suggests to do the work only on the server side)
is clearer in terms of explanations so... let me paste it here as well:
---------------------------------------------------------------
Hi,
I have someone interested in sponsoring better support for
raster printouts on high resolution devices.
Basically they want to generate an image that when printed
at 300dpi will look like what you get on the screen, which
really means you need:
- a bigger image
- scaled up labels, strokes and whatnot
- the scale computation taking into account the scale up
and ending up with the same scale denominator as the
image on the screen
This is how MapServer is doing it:
http://mapserver.org/development/rfc/ms-rfc-55.html
So they state the image size and the target dpi separately.
Seems like a sane way to proceed to me.
---------------------------------------------------------------
DeeGree and MapGuide also support this rescaling approach
using terms like resolution and dpi again:
http://trac.osgeo.org/mapguide/wiki/HttpApi/RenderingService#SetDisplayDpi1.0
http://download.deegree.org/deegree2.1/api/org/deegree/ogcwebservices/wmps/configuration/PrintMapParam.html#getTargetResolution%28%29
I understand this is quite WMS oriented... so if people don't
think it's a good idea to implement it in the rendering subsystem
straight I'll just rescale the styles in GeoServer when setting
up the map context and leave GeoTools untouched.
Otherwise the idea is to have the client code pass the dpi as
a rendering hint, and apply the RescaleStyleVisitor
using targetdpi/ogcdpi as the scale factor right after the
uom rescaling has happened (and regardless of whether there
is a uom rescaling or not).
Cheers
Andrea
--
Andrea Aime
OpenGeo - http://opengeo.org
Expert service straight from the developers.
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