[GRASS-user] Problem with display resolution / resampling / smoothing

[Sebastian Beyer]

So there is no way of changing the nearest-neighbour resampling in d.rast to lanczos for example?

> If you want optimal output, the display size needs to match the
> current region, 
How do I adjust the current region to match the display size? Region works with rows and columns, so what is the connection to my display pixels?

> Either that, or render the map at its native resolution, then resample
> using an image-processing program.
This is not an option, because I need the 'prettier' image inside GRASS to vectorize some features.


Thank you,
-- 
Sebastian Beyer


On Friday, July 8, 2011 at 6:00 AM, Glynn Clements wrote:

> 
> sleepysebi wrote:
> 
> > since April I'm working with GRASS and I think by now I got the basics.
> > Now I'm working with high resolution satellite data, looking for small
> > structures in ice.
> > My Rasterimages have got a resolution up to 2.5 meters per pixel, but most
> > of the time
> > I don't zoom in that far.
> > So the Problem is, when zoomed out GRASS doesn't displays the raster the way
> > I want it to.
> > To me it seems that it's a problem with resampling the image when
> > displaying, but I'm not shure if I'm missing something.
> > To make it clear I made a little screenshot:
> > 
> > http://imageshack.us/f/225/resamplecomparison.png/
> > 
> > So when at the same zoom lvl in EOG, it does some kind of 'smoothing' which
> > looks way better.
> > 
> > I know I can use *r.resamp.interp to resample, using lanczos for example,
> > but this is more for the final output, not for working inside GRASS
> > (vectorizing,...).
> 
> The GRASS library resamples all input maps to the current region using
> nearest-neighbour resampling. d.rast then resamples the data to the
> display (image or window) size, again using nearest-neighbour
> resampling.
> 
> If you want optimal output, the display size needs to match the
> current region, and the input map needs to be explicitly resampled to
> the current region using e.g. r.resamp.interp or r.resamp.filter.
> 
> Either that, or render the map at its native resolution, then resample
> using an image-processing program.
> 
> -- 
> Glynn Clements <glynn at gclements.plus.com (mailto:glynn at gclements.plus.com)>

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