APCA (Accessible Perceptual Contrast Algorithm) is a new method for predicting contrast for use in emerging web standards (WCAG 3) for determining readability contrast. APCA is derived form the SAPC (S-LUV Advanced Predictive Color) which is an accessibility-oriented color appearance model designed for self-illuminated displays.
APCA™ is the Accessible Perceptual Contrast Algorithm, a new way to predict contrast for text and non-text content on self-illuminated displays. This repository is for the documentation, for issue tracking, and for the discussion forum. The code, apps, variants, and supporting libraries, are in separate repos.
These are intended for end users, and those interested in a plain language overview without a lot of the math & theory.
For comments or questions see the SAPC-APCA forum here, please post all comments, questions, or discussions regarding theory, math, code, third-party tools, etc., here and not in the satellite repositories, so they can be tracked and resolved. Discussion here may eventually become part of the FAQ and guidelines.
npm i apca-w3
Maths! Vision Science! Photons on Parade!
You are here 🎯 this index page is served at the github APCA documentation repo.
Over there is the APCA W3 version, and it's the same as the published npm package "apca-w3".
The BridgePCA is backwards compatible with WCAG 2, and it's the same as the published npm package "bridge-pca".
ColorParsley is a micro library for auto parsing color strings of all kinds, also on npm.
SeeStars is a micro library for creating CIE Lstar $(L*)
$, also on npm.
DeltaPhiStar is an ultra simple general purpose contrast equation.
The canonical demo tool at Myndex
Try out the Bridge PCA tool at Myndex
Color insensitive vision simulation (aka colorblind). Includes deuteranopia, protanopia, tritanopia, and blue cone monochromacy/achromatopsia.
IRT is a California nonprofit, dedicated to developing tecnologies to improve visual accessibility for all, and home to the APCA Readability Criterion.
The APCA base color-pair formula, in math notation. 0.0.98G-4g