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=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:[email protected]] *On > Behalf Of *Erik H > *Sent:* Monday, October 16, 2017 10:58 AM > *To:* [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. >
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