SVGPathCommander

A modern set of Typescript tools for manipulating the d (description) attribute for SVGPathElement items. The library is implementing modern JavaScript API to produce reusable path strings with lossless quality. In addition, you also have a powerful tool to convert other SVG shapes like <circle> or <rect> to <path>.

While you may find familiar tools inside, this library brings new additions:

• the build in getBBox, getPointAtLength and getTotalLength are more reliable and much more accurate than the native methods, not to mention their high performance ratings;
• thanks to the community contributions we've implemented useful tools like getPropertiesAtLength, getSegmentOfPoint or isPointInStroke;
• a tool that can reverse path draw direction without altering path commands, even with specific shorthand path commands;
• a unique tool that can reverse path draw direction for path strings with only 'C' path commands;
• a new and unique tool to apply transform functions to path commands via the modern DOMMatrix API.

The key differences with other libraries:

• Typescript sourced with modernized codebase, all inherited codebase has been modernized as well;
• along with the modern codebase, the library also comes with strong TypeScript definitions;
• this library can create 3D to 2D projections, making your SVGs look like 3D but in the SVG coordinate system;
• you can use this library in both web apps and Node.js, you are not restricted to a single environment;
• path command transformations are all consistent with the SVG coordinates system, where others compute transform origin only for rotation transformation.

SVGPathCommander can use the DOMMatrix API for SVGPathElement path command transformation and implements a very fast and modernized DOMMatrix shim. There are a couple of good reasons for this implementation:

• WebKitCSSMatrix and SVGMatrix APIs are slowly pushed away by DOMMatrix, the green light for new and modern implementations;
• we can actually apply a 3D transformation matrix to SVG path commands, by calculating a 2D projection of the actual shape in 3D coordinates;
• when most tools available will be rendered absolete, we are ready for new challenges.

This library is available on CDN and npm.

Install

npm install svg-path-commander

CDN

<script src="https://cdn.jsdelivr.net/npm/svg-path-commander/dist/svg-path-commander.js">

Quick Guide

Flip a path on the X axis:

import SVGPathCommander from 'svg-path-commander';

const path = 'M0 0L100 0L50 100';

const flippedPathString = new SVGPathCommander(path).flipX().toString();
// result => 'M0 100h100L50 0'

Optimize a path string for best outcome by using the round: 'auto' option which will determine the amount of decimals based on the shape's bounding box:

const optimizedPathString = new SVGPathCommander(path, {round: 'auto'}).optimize().toString();

Or why not apply a 2D transformation and even a 3D transformation:

// a transform object
const transform = {
  translate: 15, // X axis translation
  rotate: 15, // Z axis rotation
  scale: 0.75, // uniform scale on X, Y, Z axis
  skew: 15, // skew 15deg on the X axis
  origin: [15, 0] // if not specified, it will use the default origin value [0, 0]
}
const transformed2DPathString = new SVGPathCommander(path).transform(transform).toString();

// apply a 3D transformation
const transform = {
  translate: [15, 15, 15], // `[15, 15]` would apply a 2D translation, and only `15` for X axis translation
  rotate: [15, 15, 15], // or only "15" for 2D rotation on Z axis
  scale: [0.7, 0.75, 0.8], // or only "0.7" for 2D scale on all X, Y, Z axis
  skew: [15, 15], // or only "15" for the X axis
  origin: [15, 15, 15] // full `transform-origin` for a typical 3D transformation
}
const transformed3DPathString = new SVGPathCommander(path).transform(transform).toString();

Access the bbox instance property to apply a consistent transform-origin:

// apply a 3D transformation with a consistent origin
const transformed3DPath = new SVGPathCommander(path);
const { cx, cy, cz } = transformed3DPath.bbox;
const transform = {
  translate: [15, 15, 15], // `[15, 15]` would apply a 2D translation, and only `15` for X axis translation
  rotate: [15, 15, 15], // or only "15" for 2D rotation on Z axis
  scale: [0.7, 0.75, 0.8], // or only "0.7" for 2D scale on all X, Y, Z axis
  skew: [15, 15], // or only "15" for the X axis
  origin: [cx, cy, cz] // the origin
}
const transformed3DPathString = transformed3DPath.transform(transform).toString();

SVGPathCommander comes with a full range of additional static methods, here's how to normalize a path:

const path = 'M0 0 H50';

const normalizedPath = SVGPathCommander.normalizePath(path);
// result => [['M', 0, 0], ['L', 50, 0]]

Reverse a path:

const path = 'M0 0 H50';

const reversedPath = SVGPathCommander.reversePath(path);
// result => [['M', 50, 0], ['H', 0]]

Export to string:

const myPathString = SVGPathCommander.pathToString([['M', 0, 0], ['L', 50, 0]]);
// result => 'M0 0 L50 0'

Check a path string validity:

SVGPathCommander.isValidPath(path);
// result => boolean

Check if path is a certain kind of PathArray:

SVGPathCommander.isAbsoluteArray([['M', 0, 0], ['L', 50, 0]]);
// result => true

Create a custom function to apply a 3D transformation using static methods:

import { parsePathString, getPathBBox, transformPath, pathToString } from 'svg-path-commander';

function myTransformFn(pathInput: string | PathArray, transformObject: TransformObject) {
  const path = parsePathString(pathInput);
  const { cx, cy, cz } = getPathBBox(path);

  return pathToString(
    transformPath(path, {
      ...transformObject, origin: [cx, cy, cz]
    })
  )
}

In extreme cases where performance is paramount, you can consider the parent SVG viewBox attribute to extract a bounding box required for a consistent transform origin.

// const svgViewBox = document.getElementById('my-svg').getAttribute('viewBox');
const viewBox = '0 0 24 24';

const [x, y, width, height] = viewBox.split(/\s/).map(Number);
const origin = [
  x + width / 2, // CX
  y + height / 2, // CY
  Math.max(width, height) + Math.min(width, height) / 2, // CZ
];

// use this origin for your shape transformation
const myNewString = new SVGPathCommander('M0 0 H50')
  .transform({ rotate: [35, 0, 0], origin })
  .toString();

Convert a shape to <path> and transfer all non-specific attributes

const myCircle = document.getElementById('myCircle');
SVGPathCommander.shapeToPath(myCircle, true);

Alternatively you can create <path> from specific attributes:

const myRectAttr = {
  type: 'rect',
  x: 25,
  y: 25,
  width: 50,
  height: 50,
  rx: 5
};

const myRectPath = SVGPathCommander.shapeToPath(myRectAttr);
document.getElementById('mySVG').append(myRectPath);

Server-side using jsdom:

const { document } = new JSDOM(
  `<html>
  <head></head>
  <body>
    <svg id="mySVG" viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
      <rect id="myRect" x="0" width="100" height="100" rx="15" />
    </svg>
  </body>
</html>`,
  {
    pretendToBeVisual: true,
  }
).window;

const myRect = document.getElementById('myRect');
SVGPathCommander.shapeToPath(myRect, true, document);

Get the path length:

const myPathLength = SVGPathCommander.getTotalLength('M0 0L50 0L25 50z');
// result => 161.80339887498948

Get a point along the path:

const myPoint = SVGPathCommander.getPointAtLength('M0 0L50 0L25 50z', 85);
// result => {x: 34.34752415750147, y: 31.304951684997057}

Get the path bounding box:

const myPathBBox = SVGPathCommander.getPathBBox('M0 0L50 0L25 50z');
// result => {width: 50, height: 50, x: 0, y: 0, x2: 50, y2: 50, cx: 25, cy: 25, cz: 75}

WIKI

For developer guidelines, and a complete list of static methods, head over to the wiki pages.

What Is It For?

• converting and optimizing SVGPathElement for use in third party application; our KUTE.js animation engine is using it to process SVGPathElement coordinates for SVG morphing and SVG cubic morphing;
• animators that work with SVGs and need tools for performing specific path command processing;
• front-end developers looking to spice up the content by combining, splitting or transforming paths;
• font-icon creators can use it in both Node.js and web applications to process, optimize and test their creations.

Technical Considerations

• the optimize() instance method will not merge path segments (for instance two or more cubic-bezier segments into one or more arc segments); however, the script will try to provide shorthand notations where possible, pick the shortest string for each segment, and generally try to deliver the best possible outcome;
• all tools processing path segments will never round float values, however pathToString, optimizePath and especially roundPath will always round values to the default of 4 decimals; EG: 0.56676 => 0.567, 0.50 => 0.5; you can change the default option with SVGPathCommander.options.round = 2 or remove the value rounding all together with SVGPathCommander.options.round = false; you can also control this feature via instance options;
• the getSVGMatrix utility we developed will always compute the matrix by applying the transform functions in the following order: translate, rotate, skew and scale, which is the default composition/recomposition order specified in the W3C draft;
• all 3d transformations as well as skews will convert A (arc) path commands to C (cubic bezier) due to the lack of resources;
• most tools included with SVGPathCommander should work in your Node.js apps, but feel free to report any issue;
• other path commands like R (catmulRomBezier), O, U (ellipse and shorthand ellipse) are not present in the current draft and are not supported;
• normalization can mean many things to many people and our library is developed to convert path command values to absolute and shorthand to longhand commands to provide a solid foundation for the main processing tools of our library;
• when compared to the native methods like SVGPathElement.getTotalLength() or SVGPathElement.getPointAtLength(), the output of our static methods is within a [0.002 - 0.05] margin delta, but from our experience it's proven to be a more consistent outcome.

Special Thanks

• Dmitry Baranovskiy for his Raphael.js
• Vitaly Puzrin & Alex Kocharin for their SvgPath
• Jürg Lehni & Jonathan Puckey for their Paper.js
• Andrew Willems for his awesome guide
• Mike 'Pomax' Kamermans for his awesome svg-path-reverse, bezierjs and bezierinfo
• Nicolas Debeissat for the inspiration on svg3d
• Mike Bostock for his awesome closestPoint
• James Halliday for his excelent point-at-length
• Eric Eastwood for his excelent svg-curve-lib
• PhET Interactive Simulations for their kite
• herrstrietzel for his awesome svg-pathdata-getbbox

License

SVGPathCommander is released under MIT Licence.