[Mapserver-users] Drawing Lines - Perl

[Sean Gillies]

On Jun 14, 2004, at 9:28 AM, Sidnei de Souza wrote:

> Dear all,
>
> I'm having a problem drawing lines on-the-fly with Perl mapscript and 
> haven't found anything in the list archive that can help me.
> I'm attaching a perl script that I think should work, but a blank 
> image is produced.
> I'm trying this in a RedHat Linux, with mapserver 4.2.0
> If I change the layer and shape types to POLYGON instead of LINE, a 
> correct polygon is produced.
> Any help will be very welcome!
> Thanks
> sidnei
>

Sidnei,

I am going to weave a few comments and corrections into your script.

> #!/usr/local/bin/perl
>
> use mapscript;
>
> $map = new mapscript::mapObj('') || die;
> $map->setProjection('proj=longlat');
>
>
>  $map->{width}  = 300;
>  $map->{height} = 250;
>
>  $map->{extent}->{minx} = -53.11;
>  $map->{extent}->{maxx} = -44.16;
>  $map->{extent}->{miny} = -25.30;
>  $map->{extent}->{maxy} = -19.78;
>

best practice for changing extents is to use setExtent()

   $map->setExtebt(-53.11, -25.30, -44.16, -19.78);

this is because the map's scaling needs to be recalculated
after a change of extent.

>  my $img = $map->prepareImage();
>
>  my $point = new mapscript::pointObj();
>  my $line  = new mapscript::lineObj();
>  my $shape = new mapscript::shapeObj($mapscript::MS_SHAPE_LINE);
>
>  my $layer = new mapscript::layerObj($map);
>  $layer->{'type'} = $mapscript::MS_LAYER_LINE;
>  $layer->{'name'} = 'myline';
>  $layer->{'status'} = 1;
>
>  $layer->setProjection('proj=longlat');
>
>  my $class = new mapscript::classObj($layer);
>  $class->{numstyles} = 1;
>
>  $class->{name} = 'myclass';
>  $class->{styles}->{symbol} = 0;

Access to styles has been changed in version 4.2.  The recommended
usage is now

    $class->getStyle(0)->{symbol} = 0;

>  $class->{styles}->{color}->{red} = -1;
>  $class->{styles}->{color}->{green} = -1;
>  $class->{styles}->{color}->{blue} = -1;
>

Above you will need to define real color values because a LINE type
layer is rendered using COLOR and ignores OUTLINECOLOR.  Also, as with
extents, you should use the setRGB() method

   $style = $class->getStyle(0);
   $style->setRGB(255, 0, 0);

because there is a hidden pen parameter that needs to be set.

>  $class->{styles}->{outlinecolor}->{red} = 255;
>  $class->{styles}->{outlinecolor}->{green} = 0;
>  $class->{styles}->{outlinecolor}->{blue} = 0;
>
>
>  $class->{styles}->{'minsize'} = 2;
>  $class->{styles}->{'maxsize'} = 20;
>  $class->{styles}->{'size'} = 5;
>
>  $point->{x} = -47.0608;
>  $point->{y} = -22.9056;
>  $line->add($point);
>
>  $point->{x} = -45.65;
>  $point->{y} = -24.55;
>  $line->add($point);
>
>  $point->{x} = -46.65;
>  $point->{y} = -25.55;
>  $line->add($point);
>
>  $point->{x} = -47.0608;
>  $point->{y} = -22.9056;
>  $line->add($point);
>
>  $shape->add($line);
>  $shape->draw($map,$layer,$img);
>  $layer->draw($map,$img);
>
>  $img->save('myimage.png');
>
>
>
> -- 
> Sidnei de Souza
> Diretor de Informática, CRIA
>
> "Feliz aquele que transfere o que sabe e aprende o que ensina." [Cora 
> Coralina]
>

cheers,
Sean

--
Sean Gillies
sgillies at frii dot com
http://users.frii.com/sgillies