[mapserver-users] Draw roads WITHOUT anti-aliasing

[Erik H]

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?



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
> *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=map (24-bit)
>
> -          http://maps1.dnr.state.mn.us/cgi-bin/mapserv70?map=/usr/
> local/mapserver/apps/test/palette/test.map&mode=map&map.imagetype=png8
> (8-bit w/5 colors)
>
>
>
> Steve
>
>
>
> *From:* mapserver-users [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
> *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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