[MAPSERVER-USERS] help! agg palette quantize algorithmimperfection

[Steve Lime]

I've generated palettes by rendering a large 24-bit sample image and then reducing colors using
tools like Photoshop, GIMP or ImageMagick. Then I just run gdalinfo output on the reduced color
image through a perl script to extract the palette.

#!/usr/bin/perl

$doit = 0;
while(<>) {
  if($_ =~ /Color Table/) {
    $doit = 1;
    next;
  }

  if($doit) {
    ($r,$g,$b,$a) = split /,/, substr($_,7); 
    print "$r,$g,$b\n";
  }
}

Works just fine...

Steve

>>> On 6/6/2008 at 3:24 PM, in message <17700473.post at talk.nabble.com>, BrainDrain
<paulborodaev at gmail.com> wrote:

> $? You're kidding)) Anyway, thanks for advise. Will try. 
> And what about agg rgba mode (bug, invalid color interpretation (inverting?)
> or something like that)? When
> this problem will be fixed? I need it, because I want to use map
> transparency (only rgba mode) to combine with google map layer in openlayers
> rich client app.
> 
> Stephen Woodbridge wrote:
>> 
>> Hey, that's what they pay you the BIG BUCKS for! :)
>> 
>> Write a perl/bash/{your favorite} script to grab all the COLOR lines 
>> from you mapfile and reformat the r g b to r,g,b in you palette file.
>> 
>> I have a few hundred symbols in my symbol library, but I only use about 
>> 10 of them regularly so I made sure the primary colors were also in the 
>> palette file. I make the script add them so I don't have to think about
>> it.
>> 
>> It sounds like a big deal, but it not that bad.
>> 
>> YMMV,
>>    -Steve W
>> 
>> BrainDrain wrote:
>>> 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?)
>>>>> -- 
>>>>> View this message in context:
>>>>> 
> http://www.nabble.com/help%21-agg-palette-quantize-algorithm-imperfection-tp1766773 
> 3p17667733.html
>>>>> Sent from the Mapserver - User mailing list archive at Nabble.com.
>>>>>
>>>>> _______________________________________________
>>>>> mapserver-users mailing list
>>>>> mapserver-users at lists.osgeo.org 
>>>>> http://lists.osgeo.org/mailman/listinfo/mapserver-users 
>>>>
>>>> __________________________________________
>>>>
>>>>     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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