[MAPSERVER-USERS] help! agg palette quantize algorithm imperfection

[BrainDrain]

Thanks, i already read about preparing palette index file & I see 2
obstacles:
1) I need to monitor my map file (big size) to keep relevant my palette
file. It is inflexible to extract rgb colors used in pixmap symbols
(hundreds, updatable). Can I use html palette for ex. (or any other
'universal' palette) - to make this process not so time-consuming?
2) If I have strict palette, can I be sure that agg renderer will always use
the nearest(?) color from my palette?

pagameba wrote:
> 
> Use:
> 
> OUTPUTFORMAT
>    OUTPUTFORMAT
>    NAME "AGG_Q"
>    DRIVER "AGG/PNG"
>    MIMETYPE "image/png; mode=8bit"
>    IMAGEMODE RGB
>    EXTENSION "png"
>    FORMATOPTION "PALETTE_FORCE=TRUE"
>    FORMATOPTION "PALETTE=/path/to/palette.txt"
> END
> 
> where palette.txt is a text file with RGB tuples in the form:
> 
> RRR,GGG,BBB
> 
> For example:
> 
> 0,0,0
> 255,255,255
> 127,127,127
> 
> MapServer will use AGG 24 bit rendering but reduce the output file to  
> 8 bit and reserve the colours in your palette.txt file.  This will  
> give you consistent colours for the ones you care about.   
> Specifically, you should reserve all the colours that you actually  
> reference in your map file plus any colours of pixmap symbols.  Don't  
> put in more colours than you actually need to because MapServer needs  
> to use whatever space is left (255 less your colours) for antialiasing.
> 
> Cheers
> 
> Paul
> 
> On 6-Jun-08, at 7:53 AM, BrainDrain wrote:
> 
>>
>> I use this output format in my map file:
>> OUTPUTFORMAT
>> NAME "AGG_Q"
>> DRIVER "AGG/PNG"
>> MIMETYPE "image/png; mode=8bit"
>> IMAGEMODE RGB
>> EXTENSION "png"
>> FORMATOPTION "QUANTIZE_FORCE=ON"
>> FORMATOPTION "QUANTIZE_DITHER=OFF"
>> FORMATOPTION "QUANTIZE_COLORS=256"
>> END
>> but every time map draw called (or map image requested fom cgi  
>> mapserv.exe)
>> polygons has a little difference in fill color (I think this is  
>> because
>> color palette recalculated slightly different each time). This is
>> unacceptable for me. How can i correct this? (maybe some  
>> FORMATOPTION?)
>> -- 
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>>
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>> mapserver-users at lists.osgeo.org
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> 
> 
> __________________________________________
> 
>     Paul Spencer
>     Chief Technology Officer
>     DM Solutions Group Inc
>     http://www.dmsolutions.ca/
> _______________________________________________
> mapserver-users mailing list
> mapserver-users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapserver-users
> 
> 

-- 
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