Ubuntu Manpage: Geo::GDAL::FFI - A foreign function interface to GDAL

Provided by: libgeo-gdal-ffi-perl_0.11-1build2_amd64

NAME

       Geo::GDAL::FFI - A foreign function interface to GDAL

VERSION

       Version 0.11

SYNOPSIS

       This is an example of creating a vector dataset.

        use Geo::GDAL::FFI qw/GetDriver/;

        my $sr = Geo::GDAL::FFI::SpatialReference->new(EPSG => 3067);
        my $layer = GetDriver('ESRI Shapefile')
            ->Create('test.shp')
            ->CreateLayer({
                Name => 'test',
                SpatialReference => $sr,
                GeometryType => 'Point',
                Fields => [
                {
                    Name => 'name',
                    Type => 'String'
                }
                ]
            });
        my $f = Geo::GDAL::FFI::Feature->new($layer->GetDefn);
        $f->SetField(name => 'a');
        my $g = Geo::GDAL::FFI::Geometry->new('Point');
        $g->SetPoint(1, 2);
        $f->SetGeomField($g);
        $layer->CreateFeature($f);

       This is an example of reading a vector dataset.

        use Geo::GDAL::FFI qw/Open/;

        my $layer = Open('test.shp')->GetLayer;
        $layer->ResetReading;
        while (my $feature = $layer->GetNextFeature) {
            my $value = $feature->GetField('name');
            my $geom = $feature->GetGeomField;
            say $value, ' ', $geom->AsText;
        }

       This is an example of creating a raster dataset.

        use Geo::GDAL::FFI qw/GetDriver/;

        my $tiff = GetDriver('GTiff')->Create('test.tiff', 3, 2);
        my $ogc_wkt =
               'GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS84",6378137,298.257223563,'.
               'AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,'.
               'AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,'.
               'AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]]';
        $tiff->SetProjectionString($ogc_wkt);
        my $transform = [10,2,0,20,0,3];
        $tiff->SetGeoTransform($transform);
        my $data = [[0,1,2],[3,4,5]];
        $tiff->GetBand->Write($data);

       This is an example of reading a raster dataset. Note that using PDL and MCE::Shared can
       greatly reduce the time needed to process large raster datasets.

        use Geo::GDAL::FFI qw/Open/;

        my $band = Open($ARGV[0])->GetBand;
        my ($w_band, $h_band) = $band->GetSize;
        my ($w_block, $h_block) = $band->GetBlockSize;
        my $nodata = $band->GetNoDataValue;
        my ($xoff, $yoff) = (0,0);
        my ($min, $max);

        while (1) {
            if ($xoff >= $w_band) {
                $xoff = 0;
                $yoff += $h_block;
                last if $yoff >= $h_band;
            }
            my $w_real = $w_band - $xoff;
            $w_real = $w_block if $w_real > $w_block;
            my $h_real = $h_band - $yoff;
            $h_real = $h_block if $h_real > $h_block;

            my $data = $band->Read($xoff, $yoff, $w_real, $h_real);

            for my $y (0..$#$data) {
                my $row = $data->[$y];
                for my $x (0..$#$row) {
                    my $value = $row->[$x];
                    next if defined $nodata && $value == $nodata;
                    $min = $value if !defined $min || $value < $min;
                    $max = $value if !defined $max || $value > $max;
                }
            }

            $xoff += $w_block;
        }

        say "min = $min, max = $max";

DESCRIPTION

       This is a foreign function interface to the GDAL geospatial data access library.

IMPORTABLE FUNCTIONS

       The most important importable functions are GetDriver and Open, which return a driver and
       a dataset objects respectively. GetDrivers returns all available drivers as objects.

       Other importable functions include error handling configuration (SetErrorHandling and
       UnsetErrorHandling), functions that return lists of strings that are used in methods
       (Capabilities, OpenFlags, DataTypes, ResamplingMethods, FieldTypes, FieldSubtypes,
       Justifications, ColorInterpretations, GeometryTypes, GeometryFormats, GridAlgorithms),
       also functions GetVersionInfo, HaveGEOS, SetConfigOption, GetConfigOption, FindFile,
       PushFinderLocation, PopFinderLocation, and FinderClean can be imported.

       :all imports all above functions.

   GetVersionInfo
        my $info = GetVersionInfo($request);

       Returns the version information from the underlying GDAL library. $request is optional and
       by default 'VERSION_NUM'.

   GetDriver
        my $driver = GetDriver($name);

       Returns the specific driver object.

   GetDrivers
       Returns a list of all available driver objects.

   Open
        my $dataset = Open($name, {Flags => [qw/READONLY/], ...});

       Open a dataset. $name is the name of the dataset. Named arguments are the following.

       "Flags"
           Optional, default is a reference to an empty array. Note that some drivers can open
           both raster and vector datasets.

       "AllowedDrivers"
           Optional, default is all drivers. Use a reference to an array of driver names to limit
           which drivers to test.

       "SiblingFiles"
           Optional, default is to probe the file system. You may use a reference to an array of
           auxiliary file names.

       "Options"
           Optional, a reference to an array of driver specific open options. Consult the main
           GDAL documentation for open options.

   Capabilities
       Returns the list of capabilities (strings) a GDAL major object (Driver, Dataset, Band, or
       Layer in Geo::GDAL::FFI) can have.

   OpenFlags
       Returns the list of opening flags to be used in the Open method.

   DataTypes
       Returns the list of raster cell data types to be used in e.g. the CreateDataset method of
       the Driver class.

   FieldTypes
       Returns the list of field types.

   FieldSubtypes
       Returns the list of field subtypes.

   Justifications
       Returns the list of field justifications.

   ColorInterpretations
       Returns the list of color interpretations.

   GeometryTypes
       Returns the list of geometry types.

   SetErrorHandling
       Set a Perl function to catch errors reported within GDAL with CPLError. The errors are
       collected into @Geo::GDAL::FFI::errors and confessed if a method fails. This is the
       default.

   UnsetErrorHandling
       Unset the Perl function to catch GDAL errors. If no other error handler is set, GDAL
       prints the errors into stderr.

METHODS

   get_instance
        my $gdal = Geo::GDAL::FFI->get_instance;

       Obtain the Geo::GDAL::FFI singleton object. The object is usually not needed.

LICENSE

       This software is released under the Artistic License. See perlartistic.

AUTHOR

       Ari Jolma - Ari.Jolma at gmail.com

NAME

VERSION

SYNOPSIS

DESCRIPTION

IMPORTABLE FUNCTIONS

METHODS

LICENSE

AUTHOR

SEE ALSO