What is this?

This is a library that takes general curves (expressed as line-strips) and compresses them. That is, finds a way to represent them using less vertices while aiming to maintain the original curve's shape. Please view the demo here.

Installation

Install via npm: npm install curve-compressor

The dist/ directory contains both a normal (CurveCompressor.js) as well as a minified version of the library (CurveCompressor.min.js). Include in the browser using: <script src="CurveCompressor.js"></script>

Usage

Curves as line-strips

First, represent your curve as a line-strip. That is, a sequence of vertices where each two adjacent vertices in the sequence represent a segment of the curve.

One way of doing this for a general curve is to sample it at regular intervals dt from t = 0.0 to t = 1.0. Typically dt should be small enough to represent your curve at a sufficient level of detail.

Your strip should then be an array of objects of the form {x: number, y: number}; representing the vertices in their sampling order.

Compression

Once you have a strip representative of your curve, compress it like so:

var strip = [...];
var tolerance = 0.01;
var compressed = CurveCompressor.compress_strip(strip, tolerance); 

The compression algorithm used tries to find sub-sequences of vertices on the strip that are roughly collinear - and reduces those to single line segments. For example: if in a section of the strip the sequence of points A, B, and C lie roughly on the same line, we may remove B from the strip and it will maintain its general shape (albeit not to the same degree of precision).

The parameter tolerance in compress_strip(strip, tolerance) represents the maximal angle (expressed as a fraction of Pi) between AB and BC that we are willing to tolerate losing when removing B.

That's it! compressed now contains the compressed version of the original strip. You can view this in action here.

License

This software is licensed under the MIT License. See the LICENSE file for more information.