antialiased lines with AGG

[rich.fromm]

Summary: I was previously trying to get antialiased lines working with
cartographic symbols and having no luck.  I've now switched my rendering
backend from GD to AGG and am still not able to get antialiased lines
working.

I have downloaded and installed AGG 2.5.  I realize that for licensing
reasons, mapserver is currently suggesting AGG 2.4.  Might this be
significant?  I haven't yet tried this with AGG 2.4, I had thought the issue
was just one of licensing, and not functionality.  In case it's at all
relevant, some details of my install and build experience can be found here:

http://lists.umn.edu/cgi-bin/wa?A2=ind0711&L=mapserver-users&D=1&T=0&O=D&X=5A77662D019C30E09D&Y=nospam420%40yahoo.com&P=52157
http://www.nabble.com/AGG-install-tf4390828.html#a13979959

As suggested by Stephen Woodbridge <woodbri at SWOODBRIDGE.COM>:

http://lists.umn.edu/cgi-bin/wa?A2=ind0711&L=mapserver-users&D=1&T=0&O=D&X=5A77662D019C30E09D&Y=nospam420%40yahoo.com&P=51780
http://www.nabble.com/AGG-docs-%28and-5.0.0-docs-in-general%29---tf4879380.html

I am using the following as my reference for AGG:

http://mapserver.gis.umn.edu/docs/howto/agg-rendering-specifics/?searchterm=agg

There it says:

---
All rendering is now done antialiased by default. All ANTIALIAS keywords are
now ignored
---

I have narrowed things down to a fairly small testcase, with just a single
line layer:

    LAYER
        NAME      majhwys
        DATA      MajHwys
        STATUS    DEFAULT           # DEFAULT means on
        TYPE      LINE
        CLASS
            NAME     "Major Highways"
            STYLE
                COLOR      32 32 32
            END
        END
    END

I have alternatively tried all three of the suggested PNG OUTPUTFORMAT's
from
that web page (only one at a time, of course):

    OUTPUTFORMAT
        NAME 'AGG'
        DRIVER AGG/PNG
        IMAGEMODE RGB
    END

    OUTPUTFORMAT
        NAME 'AGG'
        DRIVER AGG/PNG
        IMAGEMODE RGBA
    END

    OUTPUTFORMAT
        NAME 'AGG_Q'
        DRIVER AGG/PNG
        IMAGEMODE RGB
        FORMATOPTION "QUANTIZE_FORCE=ON"
        FORMATOPTION "QUANTIZE_DITHER=OFF"
        FORMATOPTION "QUANTIZE_COLORS=256"
    END

And I have also tried the following suggested OUTPUTFORMAT from
http://mapserver.gis.umn.edu/development/rfc/ms-rfc-32/?searchterm=AGG

    OUTPUTFORMAT
        NAME 'AGG_PNG24'
        DRIVER AGG/PNG
        IMAGEMODE RGB
    END

I have not tried JPEG, as I have not compiled with jpeg support.

Additionally, I have alternatively tried this:

    IMAGETYPE      PNG

vs. this:

    IMAGETYPE      PNG24

So 8 permutations total.  In none of the cases am I rendering antialiased
lines.

I tried adding 'ANTIALIAS TRUE' to the STYLE section (contrary to the advice
in the docs), and indeed it does not help.

Antialiased text (in a more complex example) is working for me.  And indeed
I
no longer need the 'ANTIALIAS TRUE' in the corresponding LABEL section like
I
used to with GD.  The text is indeed antialiased automatically without it
now,
like the docs claim.

But I can't get antialiased lines.  This is true if I specify no width (and
get lines of width 1), or if I specify a width with the WIDTH parameter in
the
STYLE section.

See the attached png image which was generated using the first IMAGETYPE and
first OUTPUTFORMAT shown above, and has all of the major highways in all of
CA
and NV drawn with a single pixel width. [I hope this worked, the nabble web
interface to this mailing list isn't all that clear on whether or not it
did...]

This is with mapserver-5.0.0, running on debian sarge (3.1), served via CGI
with apache2 2.0.54-5sarge1.

Thanks for any help that anyone might be able to provide.

- Rich Fromm

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