affinefit

affinefit

Fit an affine transformation to given points

Table of Contents

• Description
  • Usage
  • Example
• Contribution and License Agreement
• License
• References

Description

Fit an affine transformation to given points

This module finds, by least squares fitting, an affine transformation that (approximately) transforms given set of points/vertices/vector to another. It works with arbitrary dimensional points and requires at least dim points, when your points are dim-dimensional.

The original algorithm from Jarno Elonen [e-mail] was translated from python to javascript and can be found at python affine-fit.

Usage

var affineFit = require('affinefit')

var res
var fromPts = [[1, 1], [1, 2], [2, 2], [2, 1]]   // a 1x1 rectangle
var toPts   = [[4, 4], [6, 6], [8, 4], [6, 2]]   // scaled x 2, rotated 45 degrees and translated

var trn = affineFit(fromPts, toPts)

res = trn([1, 2])
//> [ 5.999999999999998, 5.999999999999999 ]
res = trn([1.5, 1.5])
//> [ 6, 4 ]

// to obtain the matrix in "Row echelon form" use `trn.M`
var matrix = trn.M
//> [ [ 1, 0, 0, 2, -2 ],
//>   [ 0, 1, 0, 2,  2 ],
//>   [ 0, 0, 1, 0,  4 ] ]

Example

Run the example from ./test/example.js which transforms the given svg image

using the transform

[[1, 1], [1, 2], [2, 2], [2, 1]] => [[4, 4], [6, 6], [8, 4], [6, 2]]

Contribution and License Agreement

If you contribute code to this project, you are implicitly allowing your code to be distributed under the CC0 1.0 license. You are also implicitly verifying that all code is your original work or correctly attributed with the source of its origin and licence.

License

CC0 1.0 Universal Public Domain Dedication

See LICENSE for more info.

References

• LICENSE
• python affine-fit