NAME
Geo::GDAL::FFI - A foreign function interface to GDAL
VERSION
Version 0.04
SYNOPSIS
This is an example of creating a vector dataset.
use Geo::GDAL::FFI;
my $gdal = Geo::GDAL::FFI->new();
my $sr = Geo::GDAL::FFI::SpatialReference->new(EPSG => 3067);
my $layer = $gdal
->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->Defn);
$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;
my $gdal = Geo::GDAL::FFI->new();
my $layer = $gdal->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;
my $gdal = Geo::GDAL::FFI->new();
my $tiff = $gdal->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;
my $gdal = Geo::GDAL::FFI->new();
my $band = $gdal->Open($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 = $max";DESCRIPTION
This is a foreign function interface to the GDAL geospatial data access library.
METHODS
The progress function argument used in many methods should be a reference to a subroutine. The subroutine is called with three arguments ($fraction, $msg, $data), where $fraction is a number, $msg is a string, and $data is a pointer that is given as the progress data argument.
new
my $gdal = Geo::GDAL::FFI->new;Create a new Geo::GDAL::FFI object. All GDAL functions that are available (the C API is used) are attached to this class. The other classes in this distribution are there to provide an easier to use object oriented Perl API.
Capabilities
my @caps = $gdal->Capabilities;Returns the list of capabilities (strings) a GDAL major object (Driver, Dataset, Band, or Layer in Geo::GDAL::FFI) can have.
OpenFlags
my @flags = $gdal->OpenFlags;Returns the list of opening flags to be used in the Open method.
DataTypes
my @types = $gdal->DataTypes;Returns the list of raster cell data types to be used in e.g. the CreateDataset method of the Driver class.
FieldTypes
my @types = $gdal->FieldTypes;Returns the list of field types.
FieldSubtypes
my @types = $gdal->FieldSubTypes;Returns the list of field subtypes.
Justifications
my @justifications = $gdal->Justifications;Returns the list of field justifications.
ColorInterpretations
my @interpretations = $gdal->ColorInterpretations;Returns the list of color interpretations.
GeometryTypes
my @types = $gdal->GeometryTypes;Returns the list of geometry types.
GetVersionInfo
my $info = $gdal->GetVersionInfo;Returns the version information from the underlying GDAL library.
GetDrivers
my @drivers = $gdal->GetDrivers;Returns a list of all available driver objects.
GetDriver
my @driver = $gdal->GetDriver($name);Returns the specific driver object.
Open
my $dataset = $gdal->Open($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.
LICENSE
This software is released under the Artistic License. See perlartistic.
AUTHOR
Ari Jolma - Ari.Jolma at gmail.com