NAME

SYNOPSIS

  use Geo::ShapeFile::Shape::Index;

  my $index = Geo::ShapeFile::Shape->new;
  #  $pt1 and $pt2 are point objects in this example.  
  my $segment = [$pt1, $pt2];  #  example of something to pack into the index.
  my @bbox = ($x_min, $y_min, $x_max, $y_max);
  $index->insert($segment, @bbox);

ABSTRACT

  This is a utility class for L<Geo::ShapeFile> that indexes shape objects.

DESCRIPTION

It uses a flat 2-d structure comprising a series of blocks of full width which slice the shape along the y-axis (it should really also use blocks along the x axis).

The index coordinates are simply the number of blocks across and up from the minimum coordinate specified in the new() call. These are stoed as strings jpoined by a colon, so 0:0 is the lower left. Negative block coordinates can occur if data are added which fall outside the speficied bounds. This should not affect the index, though, as it is merely a relative offset.

It is used internally by Geo::ShapeFile::Shape, so look there for examples. The method names are adapted from Tree::R to make transition easier during development, albeit the argument have morphed so it is not a drop-in replacement.

METHODS

new($n_blocks_y, @bbox)

Creates a new Geo::ShapeFile::Shape::Index objectand returns it.

$n_blocks_y is the number of blocks along the y-axis. @bbox is the bounding box the index represents (x_min, y_min, x_max, y_max).

insert($item, $min_x, $min_y, $max_x, $max_y)

Adds item $item to the blocks which overlap with the specified bounds. Returns the number of blocks the item was added to.

query_point($x, $y)

Returns an array of objects on the block contains point $x,$y. Returns an arrayref in scalar context.

get_x_max() get_x_min() get_y_max() get_y_min()

Bounds of the index, as set in the call to ->new(). There is no guarantee they are the bounds of the data, as data outside the original bounds can be indexed.

get_y_res()

Block resolution along the y-axis.

snap_to_index ($x, $y)

Returns the index key associated with point $x,$y. Does not check if it is outside the bounds of the index, so negative index values are possible.

REPORTING BUGS

SEE ALSO

AUTHOR

COPYRIGHT AND LICENSE

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.