[MAPSERVER-USERS] help! agg palette quantize algorithmimperfection

[Steve Lime]

I choose my sample image carefully and have mosaic'd a couple of them together to make sure I get most
all colors. For example:

  http://maps.dnr.state.mn.us/compass/compass_color_master.gif 

Those missing colors will be assigned the closest match if there is no room in the palette. I can't recall if extra
space in the palette is filled or not (it might). My master image allocates 128 colors and the results via tilecache 
are terrific. 

Steve


>>> On 6/7/2008 at 8:35 AM, in message <17708955.post at talk.nabble.com>, BrainDrain
<paulborodaev at gmail.com> wrote:

> hmmm, like sample map image with all layers (and most symbols) turned on?
> sounds reasonable
> That would be enough? (not all colors in sample: the nearest colors will be
> used?) Sorry for importunity.
> 
> Steve Lime wrote:
>> 
>> 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.
>>>>>>>
>>>>>>> _______________________________________________
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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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