EVOLUTION-MANAGER

Edit File: cv.dox

/*! \page create_vector Creating a vector dataset

The code here does not have any warranty. It is recommended that
before using any of this code, you look into it and try to understand
what it does, what input it needs, etc. Do not blindly execute
anything!

This example creates a new layer to a data source in memory. The layer
will contain polygon features and each feature will contain a string
as an attribute value. The name of the attribute will be 'key'. Each
polygon will have four vertices. The SRS is set to WGS84.

\code
use Geo::GDAL;

# information that we need:
my $driver = 'Memory';
my $dsname = ".";    # name of the datasource
my $lname = "boxes"; # name of the layer
my @data;            # array which contains the data as hashref items,
                     # each item comprises items 'points' and 'key'
                     # 'points' is in this case an array of four points
                     # which are refs to arrays (x,y)
                     # 'key' is a string
@data = (
    { key => 'rect1', points => [[0,0],[1,0],[1,1],[0,1]] },
    { key => 'rect2', points => [[5,5],[7,5],[7,6],[5,6]] }
    );
eval {
    $datasource = Geo::OGR::Driver($driver)->Create($dsname);
};
die "Can't create data source $dsname: $@" if $@;

$osr = Geo::OSR::SpatialReference->new(WGS => 84);

$layer = $datasource->CreateLayer(
    Name => $lname,
    SRS => $osr,
    # add the fields as in @data
    Fields => [
        { Name => 'key', Type => 'String' },
        { Name => 'geom', Type => 'Polygon' }
    ]
    );

for $item (@data) {
    my @ring = ( $item->{points}[0],
                 $item->{points}[1],
                 $item->{points}[2],
                 $item->{points}[3],
                 $item->{points}[0] # close the ring
        );
    my %feature_data = (
        key => $item->{key},
        # a polygon is an array of rings, here we define just the outer ring
        geom => { Points => [ \@ring ] }
        );
    $layer->InsertFeature(\%feature_data);
}

# check that we got it ok

$layer = $datasource->GetLayer($lname);
while ($feature = $layer->GetNextFeature()) {
    $feature->DumpReadable;
}
\endcode