[Tilecache] bad quality with 8bit AGG PNG images and metaTile=true

[Guillaume Sueur]

I would suggest you output 24bits PNG and have them reduced to 8bits
overnight with the excellent pngnq lib. (http://pngnq.sourceforge.net/)


Ivan Mincik a écrit :
> I am using UMN Mapserver WMS server version 5.2.1 which is rendering PNG images using AGG backend. They are reduced to 8bit. 
> When the Tilecache option "metaTile" is set to false, I have nice looking tiles. For the layers containing  labeIs I need to use option "metaTile=true".
> 
> Using the option "metaTile=true" for 8bit AGG PNG images gets visibly worse looking results. Can it be some problem with combination PIL and reduced 8bit images ?
> 
> Tilecache version is 2.03-1.
> 
> MapFile options are:
> 
>        OUTPUTFORMAT
>                 NAME "PNG_AGGAQ"
>                 DRIVER "AGG/PNG"
>                 MIMETYPE "image/png"
>                 IMAGEMODE RGBA
>                 FORMATOPTION "QUANTIZE_FORCE=ON"
>                 FORMATOPTION "QUANTIZE_DITHER=OFF"
>                 FORMATOPTION "QUANTIZE_COLORS=256"
>                 FORMATOPTION  "INTERLACE=OFF"
>                 TRANSPARENT ON
>         END
> 
> Tilecache config:
> [layername]
> type=WMSLayer
> url=http://server/cgi-bin/mapserv?map=map.map&transparent=true
> layers=layername
> extension=png
> debug=on
> metaTile=true
> extent_type=loose
> srs=EPSG:2065
> bbox=-273393.437500, -1256155.375000, -255811.593750, -1227652.250000
> resolutions=176.38879363894028529, 88.19439681947014265, 35.27775872778806132, 17.63887936389403066, 8.81943968194701533, 3.52777587277880578, 1.76388793638940289, 0.88194396819470144, 0.35277758727788061, 0.17638879363894031
> 
> 
> Thanks 
> Ivan
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