[mapserver-users] geotiff resampling and transparency - artifact problem

[thomas bonfort]

Hi Oliver,

Are you using mapserver's OFFSITE parameter, and/or do your tiff files have
a nodata pixel set ?
What happens if you convert your tiff to 32bit RGBA? (Not suggesting this
is a valid workaround, just trying to narrow down the reasons for this).

--
thomas


On 18 April 2013 15:27, Oliver Christen <oliver.christen at camptocamp.com>wrote:

> dear all
>
> Im having some issue when applying PROCESSING "RESAMPLE=AVERAGE" or
> "RESAMPLE=BILINEAR" on some geotiff with transparency.
> Either a clear or dark artifact appears on the border of the image, as
> seen on these examples:
>
> http://dev.camptocamp.com/**files/mapserver/fuzzy_edge_**AVERAGE.png<http://dev.camptocamp.com/files/mapserver/fuzzy_edge_AVERAGE.png>
> http://dev.camptocamp.com/**files/mapserver/fuzzy_edge_**BILINEAR.png<http://dev.camptocamp.com/files/mapserver/fuzzy_edge_BILINEAR.png>
>
> if I specify no PROCESSING at all, the transparency is correct (but not
> the image "quality" which I wanted to improve with the PROCESSING ):
> http://dev.camptocamp.com/**files/mapserver/fuzzy_edge_**NOPROCESSING.png<http://dev.camptocamp.com/files/mapserver/fuzzy_edge_NOPROCESSING.png>
>
> at first I though the problem may have been caused by a fuzzy edge on the
> transparent edges in the geotiff:
> http://dev.camptocamp.com/**files/mapserver/fuzzy_edge.png<http://dev.camptocamp.com/files/mapserver/fuzzy_edge.png>
> so I retreated one image to have clean edges:
> http://dev.camptocamp.com/**files/mapserver/clean_edge.png<http://dev.camptocamp.com/files/mapserver/clean_edge.png>
>
> but I couldnt see much difference in the result:
> http://dev.camptocamp.com/**files/mapserver/clean_edge_**AVERAGE.png<http://dev.camptocamp.com/files/mapserver/clean_edge_AVERAGE.png>
> http://dev.camptocamp.com/**files/mapserver/clean_edge_**BILINEAR.png<http://dev.camptocamp.com/files/mapserver/clean_edge_BILINEAR.png>
>
> there is no visible artifact for all border multipe of 90° (horizontal and
> vertical edges), only the non 90° edges show that problem.
>
> Im not knowledgeable with image manipulation and resampling with
> transaprency, so I dont know if this is normal or not.
>
> Any idea if there is some way to "solve" this "problem" ?
>
> thank you for your attention
>
> best regards
> Oliver
>
>
>
> --
> Camptocamp SA
> Oliver Christen
> PSE A
> CH-1015 Lausanne
>
> www.camptocamp.com
>
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>
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