line-interpolate-points

line interpolate points

A Node module that interpolates the coordinates of any number of equidistant points along a line composed of one or more line segments, at an optional offset. It's particularly useful for GIS applications, and is analogous to the PostGIS ST_LineInterpolatePoint() and Python Shapely's shapely.geometry.LineString.interpolate(). Here's an example of points interpolated over different multi-segment lines (the second group has been offset):

the api

The module exports a single function, interpolateLineRange( ctrlPoints, number, offsetDist ).

• ctrlPoints is an array of 2D point arrays, like [ [ 5, 10 ], [ 7, 10 ], [ 14, 13 ] ]
• number is the number of points to interpolate (the endpoints included)
• offsetDist is an optional distance to move each interpolated point from its container line segment.

> var interpolateLineRange = require( 'line-interpolate-points' )
> interpolateLineRange( [ [ 3, 10 ], [ 4, 10 ] ], 2 )
[ [ 3, 10 ], [ 4, 10 ] ]
> interpolateLineRange( [ [ 3, 10 ], [ 4, 10 ] ], 4 )
[ [ 3, 10 ],
  [ 3.3333333333333335, 10 ],
  [ 3.666666666666667, 10 ],
  [ 4, 10 ] ]
> interpolateLineRange( [ [ 4, 4 ], [ 4, 10 ], [ 7, 17 ] ], 6, 1 )
[ [ 3, 4 ],
  [ 3, 6.723154621172782 ],
  [ 3, 9.446309242345563 ],
  [ 3.9354486533919397, 12.387971226535829 ],
  [ 5.008151811686941, 14.890945262557498 ],
  [ 6.080854969981942, 17.393919298579167 ] ]

Install Dev Dependencies

$ npm install

Contributing

Please fork and pull request against upstream master on a feature branch. Please provide unit tests and script fixtures in the test directory.

Running Unit Tests

$ npm test

Continuous Integration

Travis tests every release against node version 0.10