Welcome!
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.
Simple Overview & QuickStart
These are intended for end users, and those interested in a plain language overview without a lot of the math & theory.
- Easy Intro to APCA? A plain-language introduction to perceptually uniform contrast.
- Bronze Simple Mode A "most basic" design guideline, intended for users migrating from WCAG 2 contrast.
Additional documentation
- APCA™ Linktree Brief curated link collection—an ideal starting point.
- APCA™ Catalog of Resources, Articles, & Links Large main catalog of articles, repos, white papers, and more!
- Main Readme Doc This page includes a discussion of the math, code walkthroughs, and links to developer related goodies. If you'd like to dive into the deep end, you could jump in here—but deep waters can be murky...
- Why APCA? A basic overview at the shallow end of the pool.
- APCA in a nutshell An early minimum user guide, largely superceeded by APC-RC
- APCA FAQ Frequently Asked Questions (work in progress)
DESIGN GUIDELINES
- The draft independent APCA Readability Criterion is up as a work in progress, still sections to be added and/or adjusted.
- Direct links to subpages:
- Bronze Simple Mode A "most basic" design guideline, intended for users migrating from WCAG 2 contrast.
- Visual Readability Contrast The multi-level conform guideline: Bronze, Silver, Gold, for basic to enhanced accessibility.
- [Non Text Contrast]() PLACEHOLDER for the non-text guidelines (coming soon!)
- Design Guide: Visual Contrast Practical design advice with examples.
- Design Guide: Paper Reading Experience (Work in progress) Guidelines for a reduced-fatigue design for light mode.
- [Design Guide: Non Text Contrast]() PLACEHOLDER Practical design advice with examples.
FORUMS
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.
TOOLS
CODE
- apca-w3 This satellite repository is the approved code intended for public guidelines, and is the only code that should be used for any development purpose.
- The code is also available as a package at
npm i apca-w3
Sciency Stuff!
Maths! Vision Science! Photons on Parade!
Social Media
Local Repo Documentation
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