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https://github.com/Myndex/SAPC-APCA

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.
https://github.com/Myndex/SAPC-APCA

accessibility apca cieluv color color-contrast color-contrast-checker color-models color-theory colorimetry contrast contrast-calculator css luminance readability srgb vision wcag wcag-contrast web

Last synced: 2 months ago
JSON representation

Host: GitHub
URL: https://github.com/Myndex/SAPC-APCA
Owner: Myndex
License: other
Created: 2019-09-18T22:25:55.000Z (over 5 years ago)
Default Branch: master
Last Pushed: 2024-05-28T00:39:41.000Z (8 months ago)
Last Synced: 2024-08-04T01:27:20.670Z (6 months ago)
Topics: accessibility, apca, cieluv, color, color-contrast, color-contrast-checker, color-models, color-theory, colorimetry, contrast, contrast-calculator, css, luminance, readability, srgb, vision, wcag, wcag-contrast, web
Language: CSS
Homepage: https://git.apcacontrast.com/documentation/APCAeasyIntro
Size: 12.8 MB
Stars: 423
Watchers: 13
Forks: 14
Open Issues: 4
Metadata Files:
- Readme: README.md
- License: LICENSE.md

Awesome Lists containing this project

awesome-list - SAPC-APCA - LAB Advanced Perceptual Contrast) is an accessibility appearance model which spawned APCA (Advanced Perceptual Contrast Algorithm) for use in emerging web standards. | Myndex | 74 | (JavaScript)

README

        






  





  





   

  





  

  






  





  

  





  

  





  



# [APCA Documentation Repo](https://github.com/Myndex/SAPC-APCA)

## 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?**](https://git.apcacontrast.com/documentation/APCAeasyIntro) A plain-language introduction to perceptually uniform contrast.

- [**Bronze Simple Mode**](https://readtech.org/ARC/tests/bronze-simple-mode/?tn=criterion) A "most basic" design guideline, intended for users migrating from WCAG 2 contrast.

### _Additional documentation_

- **APCA™ [Linktree](https://linktr.ee/Myndex)** Brief curated link collection—an ideal starting point.

- **APCA™ [Catalog of Resources, Articles, & Links](https://git.myndex.com)** Large main catalog of articles, repos, white papers, and more!

- [**Main Readme Doc**](https://git.apcacontrast.com/documentation/README) 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?**](https://git.apcacontrast.com/documentation/WhyAPCA) A basic overview at the shallow end of the pool.

- [**APCA in a nutshell**](https://git.apcacontrast.com/documentation/APCA_in_a_Nutshell) An early _minimum user guide_, largely superceeded by [APC-RC](https://readtech.org/ARC/tests/bronze-simple-mode/?tn=criterion)

- [**APCA FAQ**](https://git.apcacontrast.com/documentation/APCA_FAQ) Frequently Asked Questions (work in progress)

### _DESIGN GUIDELINES_

- The draft independent [**APCA Readability Criterion**](https://readtech.org/ARC/) is up as a work in progress, still sections to be added and/or adjusted.

- **Direct links to subpages:**

    - [**Bronze Simple Mode**](https://readtech.org/ARC/tests/bronze-simple-mode/?tn=criterion) A "most basic" design guideline, intended for users migrating from WCAG 2 contrast.

    - [**Visual Readability Contrast**](https://readtech.org/ARC/tests/visual-readability-contrast/?tn=criterion) 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**](https://readtech.org/ARC/guides/designing-with-visual-contrast/?tn=get-started) Practical design advice with examples.

    - [**Design Guide: Paper Reading Experience**](https://readtech.org/ARC/guides/paper-reading-experience/?tn=intro) (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**](https://github.com/Myndex/SAPC-APCA/discussions) 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_

- [**Color and Contrast Tools Listing**](https://git.apcacontrast.com/documentation/thirdpartytools) Many third party tools, as well as canonical technology demonstrators.

### _CODE_

- [***apca-w3***](https://github.com/Myndex/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!

- [The base APCA-W3 formula](https://github.com/Myndex/SAPC-APCA/blob/master/documentation/APCA-W3-LaTeX.md) in LaTeX math for your viewing and calculating pleasure.

- [The Realities And Myths Of Contrast And Color](https://www.smashingmagazine.com/2022/09/realities-myths-contrast-color/) color and contrast feature article at Smashing Magazine.

- [Peer Review and Third Party Analysis](https://git.apcacontrast.com/documentation/independent-review) APCA and APC-RC are derived from decades of peer-reviewed science.

- [Regarding Exponents](https://git.apcacontrast.com/documentation/regardingexponents) Is delta-gamma some kinda frat house? Nope... It's math.

- [Standard Observer Model](https://git.apcacontrast.com/documentation/StandardObserverModel) The setting for a mathematical eyeball.

- [Visual Contrast Draft Whitepaper](https://www.w3.org/WAI/GL/task-forces/silver/wiki/Visual_Contrast_of_Text_Subgroup/Whitepaper) Almost as tasty as a draft beer! This is a very early white-paper draft as part of the Visual Contrast group of Silver/WCAG 3. Here for historical reasons, the above links such as "Why APCA" provide a clearer understanding.



               






---

## Social Media

- [Myndex Research](https://twitter.com/MyndexResearch) on Twitter/X

- [Inclusive Reading Technologies](https://x.com/A11yReadTech) on Twitter/X

- [Myndex](https://techhub.social/@Myndex) on Mastodon

- [Myndex](https://www.linkedin.com/in/andrew-m-somers/) on Linkedin

- [Myndex](https://stackoverflow.com/users/10315269/myndex) on Stack Overflow

- [Myndex Gists](https://gist.github.com/Myndex) on GitHub

- [TangledWeb.xyz](https://tangledweb.xyz) related tech blog

---

## Local Repo Documentation

- [**Why APCA:**](/documentation/WhyAPCA.md) A brief plain language overview of APCA and readability contrast.

- [**Peer and Third Party Review:**](/documentation/independent-review.md) APCA and APC-RC in real world testing and review.

- [**APCA in a Nutshell:**](/documentation/APCA_in_a_Nutshell.md) Quick overview of levels, use cases, and font sizing.

- [**APCA Main Documentation (READ ME):**](/documentation/README.md) The repo basic readme file for an overview and quickstart.

- [**APCA Documentation Index:**](/documentation/) An index of relevant APCA documentation.

- [**APCA Formula 0.9.98g4g:**](https://github.com/Myndex/SAPC-APCA/blob/master/documentation/APCA-W3-LaTeX.md#latex-of-the-apca-w3-base-formula) LaTeX of the APCA formula.

- [**Repo List:**](/documentation/repoList.md) A list of specific versions of APCA, Bridge PCA, and support libraries.

- [**Standard Observer Model:**](/documentation/StandardObserverModel.md) Draft Standard Observer.

- [**Important Change Notices:**](/documentation/ImportantChangeNotices.md) General Change History (see individual repos for specifics)

- [**Regarding Exponents:**](/documentation/regardingexponents.md) Notes on the exponents used in APCA.

- [**Accessibility Statement:**](/documentation/accessibilitystatement.md) A statement for beta testers and early adopters to use place on sites using APCA 

- [**APCA Minimum Compliance for Developers:**](/documentation/minimum_compliance.md) Standards for what can be called APCA™.

- [**APCA FAQ:**](/documentation/APCA_FAQ.md) Just starting, so few Q/A yet.

### [The SAPC APCA Documentation Repository](https://github.com/Myndex/SAPC-APCA/#apca--sapc--sacam-primary-repository)

**You are here** 🎯 this index page is served at the github APCA documentation repo.

### [The APCA-W3 GitHub Repo](https://github.com/Myndex/apca-w3/)

Over there is the **APCA W3 version**, and it's the same as the published npm package "apca-w3".

### [The Bridge-PCA GitHub Repo](https://github.com/Myndex/bridge-pca/)

The **BridgePCA** is backwards compatible with WCAG 2, and it's the same as the published npm package "bridge-pca".

### [The ColorParsley GitHub Repo](https://github.com/Myndex/colorparsley/)

**ColorParsley** is a micro library for auto parsing color strings of all kinds, also on npm.

### [The SeeStars GitHub Repo](https://github.com/Myndex/seestars/)

**SeeStars** is a micro library for creating CIE Lstar $`(L*)`$, also on npm.

### [The ColorParsley GitHub Repo](https://github.com/Myndex/deltaphistar/)

**DeltaPhiStar** is an ultra simple general purpose contrast equation.

---

### [APCA Contrast Calculator](https://www.myndex.com/APCA/)

The canonical demo tool at Myndex

### [Bridge PCA Contrast Calculator](https://www.myndex.com/BPCA/)

Try out the Bridge PCA tool at Myndex

### [Myndex CVD Simulator](https://www.myndex.com/CVD/)

Color insensitive vision simulation (aka colorblind). Includes deuteranopia, protanopia, tritanopia, and blue cone monochromacy/achromatopsia.

### [Inclusive Reading Technologies, Inc.](https://readtech.org/ARC/)

**IRT is a California nonprofit**, dedicated to developing tecnologies to improve visual accessibility for all, and home to the [**APCA Readability Criterion**](https://readtech.org/ARC/).

### [Basic APCA Math in LaTeX](https://github.com/Myndex/SAPC-APCA/blob/master/documentation/APCA-W3-LaTeX.md#latex-of-the-apca-w3-base-formula)

The APCA base color-pair formula, in math notation. 0.0.98G-4g




[](https://apcacontrast.com)




[](https://readtech.org/ARC/)




[](https://github.com/Myndex/deltaphistar)




[](https://readtech.org/ARC/)




[](https://twitter.com/i/communities/1500595480790593537)




[](https://readtech.org/ARC/)