query_points.pl

Perl mapscript 3.6.4 example of creating a queryable layer of point objects, by creating them as Layer Features without an associated shape file or database connection. The points are in the perl program. The .map EXTENT must match the points you want to display. One other subtle point: The points layer in the map file must have a TEMPLATE for the layer to queryable, even thought it is not used.

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#!/usr/bin/perl
# This is an example of creating a layer of point objects (actually buoys in the Gulf of Maine, U.S.) It should be
# easily adaptable to any set of points.  It creates the points as features in the layer which means that they
# can still be retrieved using $layer->queryByPoint() even though no shape file or database connection exists
# for them. The layer has a connectiontype of MS_INLINE
# Author: Eric Bridger eric@gomoos.org eric@maine.com
# This has only been tested with mapserver 3.6.4

use strict;
use mapscript;
use CGI ":cgi";

my $q = new CGI;
my $msg = '';

# A hash of points. First field will be the label.
my %points = (
    J0202 =>    {'longitude' => -67.0173,
                'latitude'  => 44.8911,
                },
    K0103 =>    {'longitude' =>  -66.0146,
                'latitude' => 45.2045,
                },
    E0105 =>    {'longitude' => -68.3578,
                'latitude' => 43.7148,
                },
    L0102 =>    {'longitude' => -66.5528,
                'latitude' => 43.6243,
                },
    F0105 =>    {'longitude' => -68.9983,
                'latitude' => 44.0555,
                },
    M0102 =>    {'longitude' => -67.8800,
                'latitude' => 43.4900,
                },
    A0104 =>    {'longitude' => -70.5665,
                'latitude' => 42.5185,
                },
    B0103 =>    {'longitude' => -70.4278,
                'latitude' => 43.1807,
                },
    I0104 =>    {'longitude' => -68.1087,
                'latitude' => 44.1058,
                },
    C0202 =>    {'longitude' => -70.0578,
                'latitude' => 43.5673,
                },
);

my $image_name = sprintf("%0.10d",rand(1000000000)) . ".png";
# see points.map
my $map = new mapscript::mapObj("query_points.map");

if(!$map){
    warn "New mapObj() error: $mapscript::ms_error->{message}\n";
}

# Create a point object representing the mouse click on the map.
my ($x, $y) = get_click($q, $map);

my $click_pt = undef;
if($x != 0 && $y != 0){
    $click_pt = new mapscript::pointObj();
    $click_pt->{x} = $x;
    $click_pt->{y} = $y;
}

my $img = $map->prepareImage();

if(!$img){
    warn "prepareImage() error: $mapscript::ms_error->{message}\n";
}

my $layerObj = undef;

# Add points as Features to the point layer. Save any info in a lookup table. The shape objects and the
# index into the lookup table will be the same.
$layerObj = $map->getLayerByName('points');
my $point = new mapscript::pointObj();

# Queries will return index into this array.
my @point_lookup = ();
my $i = 0;
foreach my $point_id (keys %points){
    $point->{x} = $points{$point_id}{longitude};
    $point->{y} = $points{$point_id}{latitude};
    # Features require shape objects, which require lines, so create a single point line.
    my $line = new mapscript::lineObj();
    $line->add($point);
    my $shp = new mapscript::shapeObj($mapscript::MS_SHAPE_POINT);
    $shp->add($line);
    $shp->setBounds();
    $shp->{text} = $point_id;
    # set the shape index to the index into our lookup table.
    $shp->{index} = $i;
    if($layerObj->addFeature($shp) == -1){
        warn "addFeature failed\n";
    }
    push @point_lookup, $point_id;
    $i++;
}

# add layer to map img.
$layerObj->draw($map, $img);


# Query based on the mouse click point.
if($click_pt){
    my $record = -1;
    $msg .= "<p>\n";
    $layerObj = $map->getLayerByName('points');
#   $msg .= "tolerance $layerObj->{tolerance}<br>\n";
#   $msg .= "connection type $layerObj->{connectiontype} ";
#   if($layerObj->{connectiontype} == $mapscript::MS_INLINE){
#       $msg .= " INLINE<br>";
#   }
#   if($layerObj->{connectiontype} == $mapscript::MS_SHAPEFILE){
#       $msg .= " SHAPEFILE<br>";
#   }

    if($layerObj->queryByPoint($map,$click_pt,$mapscript::MS_SINGLE,0)){
        $msg .= "No Points found<br>\n";
    }else{
        my $results = $layerObj->{resultcache};
        my $num_results = $results->{numresults};
        $msg .= "Found $num_results points.<br>\n";
        # we only expect one result.
        my $rslt = $layerObj->getResult(0);
        # this is an index into the point lookup table.
        my $record = $rslt->{shapeindex};
        my $point_name = $point_lookup[$record];
        $msg .= "Click found point: $point_name.<br>\n";
    }
    $msg .= "</p>\n";

}

# display the click point
if($click_pt){
    $layerObj = $map->getLayerByName('click');
    $click_pt->draw($map, $layerObj, $img, undef, "Click");
}


$map->drawLabelCache($img);

$img->saveImage($image_name, $mapscript::MS_PNG, $map->{transparent}, $map->{interlace}, 0);

$img->free();

# Output the HTML form and map

print $q->header();
print $q->start_html(-title=>'MapServer - Dynamic Points', -bgcolor=>"#ffffff");

print "<form name=\"pointmap\" action=\"query_points.pl\" method=\"GET\">\n";
print "<table border=\"1\" cellpadding=\"5\" cellspacing=\"2\">\n";
print "<tr>\n";
print "<td>\n";
print "<input border=\"2\" type=\"image\" name=\"img\" src=\"$image_name\">\n";
print "</td>\n";
print "</tr>\n";
print "</table>\n";
print "</form>\n";
print "$msg<br>\n";
print "<a href=\"query_points.pl\"> Start over </a><br>\n";
print "<p><br><br><br></p>\n";

print $q->end_html();
# translate mouse click x,y into map longitude, latitude based on map extent. This is based on set_extent() in
# mapquakes.pl

sub get_click {
    my ($q, $map) = @_;
    my ($x, $y, $cx, $cy) = (0,0,0,0);
    my $minx = $map->{extent}->{minx};
    my $miny = $map->{extent}->{miny};
    my $maxx = $map->{extent}->{maxx};
    my $maxy = $map->{extent}->{maxy};

    if($q->param('img.x')) { # Make sure we got a click
        $x = $q->param('img.x');
        $y = $q->param('img.y');

        $cx = ($maxx-$minx)/($map->{width}-1); # calculate cellsize in x and y
        $cy = ($maxy-$miny)/($map->{height}-1);

        $x = $minx + $cx*$x; # change x,y from image to map coordinates
        $y = $maxy - $cy*$y;
    }

    return ($x, $y);
}

query_points.map

MAP
  STATUS ON
  EXTENT -71.5 39.5 -63.0 46.0
  SIZE 504 385
  IMAGETYPE PNG
  UNITS DD

SYMBOL
  TYPE ELLIPSE
  NAME "circle"
  POINTS 1 1 END
  FILLED TRUE 
END

SYMBOL
  TYPE VECTOR
  NAME "plus"
  POINTS .5 0 .5 1 -99 -99 0 .5 1 .5 END
END 

LAYER 
  NAME "points"
  TYPE POINT
  STATUS ON
  TOLERANCE 10
  # Need fake template for querys to work
  TEMPLATE "bogus.html"
  CLASS
    NAME "buoy"
    SYMBOL "circle"
    SIZE  8
    COLOR 255 0 0
    OUTLINECOLOR 0 0 0
    LABEL
      COLOR 255 0 0
      TYPE BITMAP
      SIZE MEDIUM
      POSITION AUTO
      PARTIALS FALSE
      BUFFER 2
    END # end of label
  END
END
LAYER
  NAME "click"
  TYPE POINT
  STATUS ON
  CLASS
    NAME "click"
    SYMBOL "plus"
    SIZE  6
    COLOR 0 0 0
    LABEL
      TYPE BITMAP
      SIZE TINY
      COLOR 0 0 0
      POSITION AUTO
      PARTIALS FALSE
      BUFFER 1
    END
  END
END

END

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