[mapserver-users] Draw roads WITHOUT anti-aliasing

Tue Oct 17 01:53:03 PDT 2017

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:mapserver-users-bounces at lists.osgeo.org] Im
> Auftrag von Richard Greenwood
> Gesendet: Dienstag, 17. Oktober 2017 03:44
> An: Erik H
> Cc: mapserver-users at lists.osgeo.org
> Betreff: Re: [mapserver-users] Draw roads WITHOUT anti-aliasing
> 
> On Mon, Oct 16, 2017 at 1:23 PM, Erik H <erik.h11.01 at gmail.com> 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)
> <steve.lime at state.mn.us> 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:erik.h11.01 at gmail.com]
> 		Sent: Monday, October 16, 2017 1:15 PM
> 		To: Lime, Steve D (MNIT) <steve.lime at state.mn.us>
> 		Cc: mapserver-users at lists.osgeo.org <mailto:mapserver-
> users at lists.osgeo.org>
> 		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)
> <steve.lime at state.mn.us> 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-
> bounces at lists.osgeo.org <mailto:mapserver-users-bounces at lists.osgeo.org>
> ] On Behalf Of Erik H
> 			Sent: Monday, October 16, 2017 10:58 AM
> 			To: mapserver-users at lists.osgeo.org <mailto:mapserver-
> users at lists.osgeo.org>
> 			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.
> 
> 
> 
> 
> 
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> 
> 
> 
> 
> --
> 
> Richard W. Greenwood, PLS
> www.greenwoodmap.com