antialiasing line features..

[thomas bonfort]

actually there's a smarter fix, but that still requires patching gd.c
without trying it and seeing if it stops your problem, I can't say
much more wether it corresponds to your case or not.
you'll have to download and patch the last version of gd, and make
sure mapserv is linked to the patched version.

the patch is to add this near line 3035 of gd.c at the beginning of
static void gdImageSetAAPixelColor(gdImagePtr im, int x, int y, int
color, int t)

if(x<0||y<0||x>=im->sx||y>=im->sy)
{
       return;
}


cheers,
tb


On 11/2/05, Dylan Beaudette <dylan at iici.no-ip.org> wrote:
> Interesting...
>
> I am having sporadic segfaults from mapserv, especially when there are a lot
> of line features, that are set to use antialiasing...
>
> Any ideas if this is related to your problems?
>
> Note that maps are generated fine for lines with few elements...
>
> Dylan
>
>
> On Tuesday 25 October 2005 11:55 pm, thomas bonfort wrote:
> > hi list,
> > I'm also having problems with mapserver or mapscript dying on certain
> > antialiased lines. I think I tracked the bug down to gd, I still have
> > to find the time to find out in what cases it happens. For those
> > interrested, for me gd segfaults for me in file gd.c on line 3055,
> > because it is called with out of bounds values for pixel position. the
> > call is being made on lines 3098 or 3119, with the argument
> > (y>>16)+1 (line 3098)
> > or
> > (x>>16)+1 (line 3119)
> > which seems to me to be out of image bounds.
> >
> > My fix is to set the clipping regions of lines 3069-3071 to 1 pixel
> > inside, which is a quick workaround which prevents the segfaults, but
> > produces poor quality for short line segments.
> >
> > cheers,
> > tb
> >
> > On 10/26/05, Flavio Hendry <flavio at tydac.ch> wrote:
> > > hi Abe
> > >
> > > as said, I had problems with it (hanging mapserver). and the ones which
> > > seemed to work, I did not see a difference (was using jpeg as output).
> > > png24 is no option, resulting size of images too large.
> > >
> > > Mit freundlichem Gruss / Best Regards
> > > Flavio Hendry
> > >
> > > ----------------------------------------------------------------
> > > TYDAC NEWS http://www.tydac.ch/german/index.php?menu=News_actual
> > > ----------------------------------------------------------------
> > > ############ Mit freundlichen Gruessen / Kind Regards
> > > ############ mailto:flavio at tydac.ch
> > > ############ TYDAC AG - http://www.tydac.ch
> > > #### #### Geographic Information Solutions
> > > #### #### Luternauwg 12 -- CH-3006 Bern
> > > ############ Tel +41 (0)31 368 0180 - Fax +41 (0)31 368 1860
> > > ----------------------------------------------------------------
> > >
> > >
> > > -----Original Message-----
> > > From: Abe Gillespie <abe.gillespie at GMAIL.COM>
> > > To: MAPSERVER-USERS at LISTS.UMN.EDU
> > > Date: Tue, 25 Oct 2005 12:11:00 -0400
> > > Subject: Re: [UMN_MAPSERVER-USERS] antialiasing line features..
> > >
> > > > Hey everyone,
> > > >
> > > > Sorry, a somewhat OT - This thread has piqued my interest a little.
> > > > Would someone mind posting examples of aliased vs. antialiased
> > > > images?
> > > >  I'm just curious about the results you can get.
> > > >
> > > > Thanks!
> > > > -Abe
> > > >
> > > > On 10/25/05, Dylan Beaudette <dylan at iici.no-ip.org> wrote:
> > > > > On Oct 25, 2005, at 2:54 AM, Flavio Hendry wrote:
> > > > > > Ciao Giorgio
> > > > > >
> > > > > > It might not be the antialiasing but the png24. png24 files tend
> > > >
> > > > to get
> > > >
> > > > > > very large, i.e. 400k compared to 70k as a JPEG (check your
> > > >
> > > > output
> > > >
> > > > > > directory). Maybe you try JPEG.
> > > > > >
> > > > > > However, I had quite problems with the antialiasing, working on
> > > >
> > > > some
> > > >
> > > > > > layer and on some the system hung (no error messages, just
> > > >
> > > > hanging when
> > > >
> > > > > > zooming). Removing the antialiasing from the layer worked.
> > > >
> > > > Strange
> > > >
> > > > > > behaviour, anybody having this problem?
> > > > > >
> > > > > > Mit freundlichem Gruss / Best Regards
> > > > > > Flavio Hendry
> > > > > >
> > > > > > ----------------------------------------------------------------
> > > > > > TYDAC NEWS http://www.tydac.ch/german/index.php?menu=News_actual
> > > > > > ----------------------------------------------------------------
> > > > > > ############ Mit freundlichen Gruessen / Kind Regards
> > > > > > ############ mailto:flavio at tydac.ch
> > > > > > ############ TYDAC AG - http://www.tydac.ch
> > > > > > #### #### Geographic Information Solutions
> > > > > > #### #### Luternauweg 12 -- CH-3006 Bern
> > > > > > ############ Tel +41 (0)31 368 0180 - Fax +41 (0)31 368 1860
> > > > > > ----------------------------------------------------------------
> > > > >
> > > > > Yes. I am noticing a seemingly erratic behavior: If I enable
> > > > > antialiasing with JPEG output format, it does not work. If I enable
> > > > > antialiasing in a tiled line layer it does not work...
> > > > >
> > > > > Are there some good ground rules for antialiasing? i.e. ONLY PNG24,
> > > > > etc. ?
> > > > >
> > > > > Thanks!
> > > > >
> > > > > --
> > > > > Dylan Beaudette
> > > > > Soils and Biogeochemistry Graduate Group
> > > > > University of California at Davis
> > > > > 530.754.7341
>
> --
> Dylan Beaudette
> Soils and Biogeochemistry Graduate Group
> University of California at Davis
> 530.754.7341
>