[mapserver-users] Draw roads WITHOUT anti-aliasing

[Eichner, Andreas - SID]

Nope, this won't work:

  r->default_gamma = atof(msGetOutputFormatOption( format, "GAMMA", "0.75" ));
  if(r->default_gamma <= 0.0 || r->default_gamma >= 1.0) {
    r->default_gamma = 0.75;
  }

From mapagg.cpp lines 844-847 forces 0 < GAMMA < 1
Also note that MapServer uses a linear gamma function defined as

       double operator() (double x) const
        {
            if(x < m_start) return 0.0;
            if(x > m_end) return 1.0;
            return (x - m_start) / (m_end - m_start);
        }

Where m_start is _always_ set to 0 and m_end is set to the GAMMA value given by you (or the default 0.75).
I think someone should check this - to me it seems a power function was intented...

HTH

> -----Ursprüngliche Nachricht-----
> Von: mapserver-users [mailto:mapserver-users-bounces at lists.osgeo.org] Im
> Auftrag von lars.schylberg at blixtmail.se
> Gesendet: Mittwoch, 18. Oktober 2017 14:05
> An: mapserver-users at lists.osgeo.org
> Betreff: Re: [mapserver-users] Draw roads WITHOUT anti-aliasing
> 
> Hi,
> 
> 
> 
> 
> I did some quick tests with :
> 
> 
> 
> 
>   OUTPUTFORMAT
>     NAME "png_G0"
>     DRIVER AGG/PNG
>     MIMETYPE "image/png"
>     IMAGEMODE RGB
>     EXTENSION "png"
>     FORMATOPTION "GAMMA=0.0"
>   END
> 
> 
> 
> 
> and shp2img with options -i
> 
> 
> eg: shp2img -m 01_polygon_td_poly.map -o 01_polygon_td_poly.png -i
> png_G0
> 
> 
> 
> 
> 
> I did some tests with both polygons, polygon outlines and lines and they
> all seems to have anti-aliasing as far as I could see.
> 
> Would this be an ok way to test it?  I also have some people that would
> like to do lines without anti-aliasing for a strange reason.
> 
> 
> 
> 
> 
> Lars Schylberg
> 
> 
> 
> 
> 
> -----Originalmeddelande-----
> > Från: "Rahkonen Jukka (MML)" <jukka.rahkonen at maanmittauslaitos.fi>
> > Till: "Eichner, Andreas - SID" <Andreas.Eichner at sid.sachsen.de>, "Erik
> H" <erik.h11.01 at gmail.com>
> > Kopia: mapserver-users at lists.osgeo.org
> > Datum: 2017-10-18 11:13
> > Ämne: Re: [mapserver-users] Draw roads WITHOUT anti-aliasing
> >
> > Hi,
> >
> > I suppose that the amount of antialiasing with AGG is set with "gamma"
> parameter.  Mapserver supports that at least for polygons as documented
> in http://www.mapserver.org/mapfile/outputformat.html but you could try
> if using gamma=0.0 has an effect on lines as well. It may be that it
> does not because search
> >
> https://github.com/mapserver/mapserver/search?utf8=%E2%9C%93&q=gamma&typ
> e=
> > seems to find only something that is tied to polygon outlines
> > https://github.com/mapserver/mapserver/blob/branch-7-
> 0/renderers/agg/include/agg_renderer_outline_aa.h
> >
> >
> > If gamma does not work for lines then it could be worth making a
> feature request for adding a new formatoption "GAMMA_LINE=[].
> >
> > Couple of Mapnik links dealing with the same issue:
> > http://gis.19327.n8.nabble.com/Turning-off-anti-aliasing-
> td5339458.html
> > http://mapnik.org/mapnik-reference/#3.0.6/line-gamma-method
> >
> > -Jukka Rahkonen-
> >
> >
> >
> > -----Alkuperäinen viesti-----
> > Lähettäjä: mapserver-users [mailto:mapserver-users-
> bounces at lists.osgeo.org] Puolesta Eichner, Andreas - SID
> > Lähetetty: 18. lokakuuta 2017 9:57
> > Vastaanottaja: Erik H <erik.h11.01 at gmail.com>
> > Kopio: mapserver-users at lists.osgeo.org
> > Aihe: Re: [mapserver-users] Draw roads WITHOUT anti-aliasing
> >
> > Damn... missed attaching the images.
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: mapserver-users [mailto:mapserver-users-
> bounces at lists.osgeo.org]
> > > Im Auftrag von Eichner, Andreas - SID
> > > Gesendet: Mittwoch, 18. Oktober 2017 08:28
> > > An: Erik H
> > > Cc: mapserver-users at lists.osgeo.org
> > > Betreff: Re: [mapserver-users] Draw roads WITHOUT anti-aliasing
> > >
> > > Hi,
> > >
> > > I just meant that it seems to be pretty easy to implement aliased
> > > rendering with AGG.
> > > Simply changing the typedef in line 91 of mapagg.cpp from
> > >
> > >   typedef mapserver::renderer_scanline_aa_solid<renderer_base>
> > > renderer_scanline;
> > >
> > > to
> > >
> > >   typedef mapserver::renderer_scanline_bin_solid<renderer_base>
> > > renderer_scanline;
> > >
> > > turns of anti-aliased rendering. I've attached the output of
> "shp2img
> > > -m line_simple.map" from the msautotests.
> > > An additional member in class AGG2Renderer for the aliased
> rasterizer
> > > and conditionally passing one or the other to render_scanlines()
> > > depending on some value of strokeStyleObj might be enough.
> > >
> > > Regards
> > >
> > > > -----Ursprüngliche Nachricht-----
> > > > Von: Erik H [mailto:erik.h11.01 at gmail.com]
> > > > Gesendet: Dienstag, 17. Oktober 2017 17:34
> > > > An: Eichner, Andreas - SID
> > > > Cc: Richard Greenwood; mapserver-users at lists.osgeo.org
> > > > Betreff: Re: [mapserver-users] Draw roads WITHOUT anti-aliasing
> > > >
> > > > As for Andreas' remark about 'simply the use of another scanline
> > > > rasterizer.' - I'm sorry but I'm not much of a C++ developer. If I
> > > have
> > > > to do rasterizing, I'd skip MapServer altogether and generate the
> > > > PNG
> > > in
> > > > Java.
> > > >
> > > _______________________________________________
> > > mapserver-users mailing list
> > > mapserver-users at lists.osgeo.org
> > > https://lists.osgeo.org/mailman/listinfo/mapserver-users
> > _______________________________________________
> > mapserver-users mailing list
> > mapserver-users at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/mapserver-users
> 
> 
> 
> 
> 
> 
> 
> --
> 
>