Library for common CIE color difference measurements
npm install empfindungempfindung
==========
A library for calculating the perceptual difference between colors (∆E). _Empfindung_ is German for 'sensation', and its use in the context of color difference measurement stems from the ilk of Messrs. Hermann von Helmhotz and Ewald Hering.
The following measurements are supported:
- CIE76 (1976)
- CIE94 (1994)
- CIEDE2000 (2000)
- CMC l:c (1984)
All calculations are performed in either L\a\b or L\C\H\ space (as the metrics prescribe).
Why, we exist only to serve!
A closer look reveals that the CIEDE2000 calculations are... numerous. But we bravely proceed. Another attempt already exists here, but it does not implement the rest of the metrics. This version implements everything on the Wikipedia page with good test coverage.
This library is available on NPM, like so:
``shell`
npm install --save empfindung
To use it, simply require the package:
`javascript
import DeltaE from empfindung;
DeltaE.cie1976([50, 25, 39], [80, 12, 93]); // returns ~63.127
DeltaE.cie1994([55, 60, 48], [55, 65, 53], 'graphicArts'); // returns ~1.61
DeltaE.cie1994([55, 60, 48], [55, 65, 53], 'textiles'); // returns ~1.54
DeltaE.ciede2000([55, 60, 48], [55, 65, 53]); // returns ~1.58
DeltaE.cmc1984([55, 60, 48], [55, 65, 53], 'acceptability'); // returns ~2.339
DeltaE.cmc1984([55, 60, 48], [55, 65, 53], 'imperceptibility'); // returns ~2.339
`
Tests and code coverage use ava and nyc respectively. Running npm test will do the honors.
Code style is enforced using ESLint, and running npm run prebuild will lint the source files in an ES6-compliant manner.
_Detailed JSDoc comments accompany each function inline, if you so desire._
The color difference metrics are implemented via the following functions:
- CIE76: cie1976(a, b)
- CIE94:
- CIEDE2000:
- CMC l:c:
The first two inputs for any function (a and b, or ref and sample) should be a pair of arrays corresponding to 3-channel colors in L\a\b\* space. The nomenclature is exactly [L, A, B]. If a color with more than 3 channels is provided (normally because there is some kind of opacity/alpha channel that wasn't stripped), ChannelCountError will be thrown. If each channel falls outside the acceptable domain (normally because the color has not been converted from RGB), CoordinateRangeError will be thrown.
CIE94 and CIEDE2000 are asymmetric measurements, hence the first input is the reference color (ref), and the second input is the sampled color (sample).
CIE94 and CMC l:c also accept an optional parameter adjusting the metric for the kind of quasimetric being evaluated. CIE94 offers an application type choice (via applicationType) of either 'graphicArts' or 'textiles' for their eponymous use. CMC l:c offers a threshold choice (via threshold) of either 'acceptability' or 'imperceptibility' that nuances the just-noticeable difference between the colors. In both cases, the bolded option is the default if nothing is specified.
Development will be maintained under the Semantic Versioning guidelines as much as possible in order to ensure transparency and backwards compatibility.
Releases will be numbered with the following format:
And constructed with the following guidelines:
+ Breaking backward compatibility bumps the major (and resets the minor and patch)
+ New additions without breaking backward compatibility bump the minor (and resets the patch)
+ Bug fixes and miscellaneous changes bump the patch
For more information on SemVer, visit http://semver.org/.
Have a bug or a feature request? Please open a new issue.
Before opening any issue, please search for existing issues and read the Issue Guidelines.
Please submit all pull requests against \*-wip branches. All code should pass ESLint validation using the .eslintrc file that is provided. To make life easy for everyone, use indentation guidelines specified in .editorconfig. Note that files in /lib` are written in ES2015 syntax.
The MIT License (MIT)
Copyright (c) 2016 Kenneth Lim
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