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Geo::ShapeFile::Shape - Geo::ShapeFile utility class.
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);
This is a utility class for L<Geo::ShapeFile> that indexes shape objects.
This is a 2-d block-based index class for Geo::ShapeFile::Shape objects. It probably has more generic applications, of course.
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.
None by default.
- 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.
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.
Please send any bugs, suggestions, or feature requests to https://github.com/shawnlaffan/Geo-ShapeFile/issues.
Shawn Laffan, <email@example.com>
Copyright 2014 by Shawn Laffan
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.