I'd guess it's simply the use of another scanline rasterizer. The demo http://www.antigrain.com/demo/rasterizers.cpp.html is an example of drawing as polygon aliased and anti-aliased side by side.
> -----Ursprüngliche Nachricht----- > Von: mapserver-users [mailto:[email protected]] Im > Auftrag von Richard Greenwood > Gesendet: Dienstag, 17. Oktober 2017 03:44 > An: Erik H > Cc: [email protected] > Betreff: Re: [mapserver-users] Draw roads WITHOUT anti-aliasing > > On Mon, Oct 16, 2017 at 1:23 PM, Erik H <[email protected]> wrote: > > > I don't think we have much use for lines that are one pixel wide. > > I'm surprised at how difficult this is; isn't there some driver > other than AGG/PNG I could use? > > > In mapserver versions before 7.0 there is the GD driver. I use it for 8 > bit GIFs. Not sure what it does with 24 images. > > Rich > > > > > > > On Mon, Oct 16, 2017 at 2:50 PM, Lime, Steve D (MNIT) > <[email protected]> wrote: > > > So you really do need 24-bit output. I was looking back > through the mailing list archives and it was mentioned back in 2012 that > aliased output could be implemented for simple (1 pixel-wide) lines and > polygons – so there is hope but I don’t believe (looking through the > source) that Thomas ever fully implemented it. In mapagg.cpp there are > ifdef’s for a symbol named AGG_ALIASED_ENABLED which makes me wonder if > work was started. I tried setting that in mapagg.cpp but ran into > compile errors and didn’t try and track those down. > > > > Of course you’d have to live with 1 pixel wide lines… > > > > Steve > > > > From: Erik H [mailto:[email protected]] > Sent: Monday, October 16, 2017 1:15 PM > To: Lime, Steve D (MNIT) <[email protected]> > Cc: [email protected] <mailto:mapserver- > [email protected]> > Subject: Re: [mapserver-users] Draw roads WITHOUT anti- > aliasing > > > > Thanks for your reply, but I should have mentioned that I > have a LOT of different colors to be displayed, almost a million... > > > > I should also have mentioned that I've already tried to > filter out the anti-aliased pixels by setting all alpha bytes to 255 and > then assuming that all pixels that don't have alpha=255 in the PNG can > be removed, but that assumption seems to be wrong. > > > > On Mon, Oct 16, 2017 at 2:00 PM, Lime, Steve D (MNIT) > <[email protected]> wrote: > > Hmmm… I wonder if you just could use a pre-computed > palette to control quantizing to 8 bits. You can supply a palette file > (RGB or RGBA) and the MapServer will map 24/32-bit values to those in > the palette. Format options are: > > > > FORMATOPTION "PALETTE_FORCE=TRUE" > > FORMATOPTION "PALETTE=palette.txt" > > > > This will definitely limit the colors in your output > image to those you specify. The question is whether or not the anti- > aliased colors will map to the right color and that will depend on your > palette. I did write a simple test with a 5 color palette (black, white, > red, green and blue) and it seems to work ok but that’s a very simple > palette… Based on your application it might work though. > > > > - http://maps1.dnr.state.mn.us/cgi- > bin/mapserv70?map=/usr/local/mapserver/apps/test/palette/test.map&mode=m > ap <http://maps1.dnr.state.mn.us/cgi- > bin/mapserv70?map=/usr/local/mapserver/apps/test/palette/test.map&mode=m > ap> (24-bit) > > - http://maps1.dnr.state.mn.us/cgi- > bin/mapserv70?map=/usr/local/mapserver/apps/test/palette/test.map&mode=m > ap&map.imagetype=png8 <http://maps1.dnr.state.mn.us/cgi- > bin/mapserv70?map=/usr/local/mapserver/apps/test/palette/test.map&mode=m > ap&map.imagetype=png8> (8-bit w/5 colors) > > > > Steve > > > > From: mapserver-users [mailto:mapserver-users- > [email protected] <mailto:[email protected]> > ] On Behalf Of Erik H > Sent: Monday, October 16, 2017 10:58 AM > To: [email protected] <mailto:mapserver- > [email protected]> > Subject: [mapserver-users] Draw roads WITHOUT anti- > aliasing > > > > I'm running a tiling server that uses MapServer 7.0.4 > to generate PNGs. > > > > My colleagues came up with an ingenious idea to animate > traffic conditions that would require them to identify road segments > based on their color. They asked me to generate tiles with a > predetermined RGBA value per road segment. > > > > I configured a layer of type LINE, with a STYLE section > containing 'COLOR [palette]' (palette being a field in the database > query). Initially, I thought I was creating the images my colleagues > needed, but it seems that the anti-aliasing causes some pixels to have > colors other than the one I specified; this prevents us from identifying > the road segments. > > > > We can live without anti-aliasing, but I was unable to > turn it off; I tried both the AGG/PNG and GD/PNG drivers and messed with > various FORMATOPTION identifiers, but nothing seemed to make any > difference. > > > > Any suggestions? > > > > Thanks. > > > > > > _______________________________________________ > mapserver-users mailing list > [email protected] <mailto:mapserver- > [email protected]> > https://lists.osgeo.org/mailman/listinfo/mapserver-users > <https://lists.osgeo.org/mailman/listinfo/mapserver-users> > > > > > > -- > > Richard W. Greenwood, PLS > www.greenwoodmap.com _______________________________________________ mapserver-users mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/mapserver-users
