Create new technique for new contrast formula (threshold value)

[alastc]

One approach to dealing with the updated colour contrast value is to add a new technique using the new value, making it a sufficient one for the contrast criteria.
https://www.w3.org/2020/07/14-ag-minutes.html#item07

[bruce-usab]

Deprecated formula is currently referenced in Note to glossary reference for relative luminance, see:
https://www.w3.org/TR/WCAG21/#dfn-relative-luminance

Three instances:

if RsRGB <= 0.03928 ...
if GsRGB <= 0.03928 ...
if BsRGB <= 0.03928 ...

Should be:

if RsRGB <= 0.04045 ...
if GsRGB <= 0.04045 ...
if BsRGB <= 0.04045 ...

See Issue #360 for the long version.

Here is a graphic of the formula from Issue w3c/wcag3#192

[alastc]

Hi @bruce-usab, I think the task was to create a technique (maybe based on G18?) that would use the newer value.

That could be copy-paste G18 into a Google doc and highlight the updates you make, or:

• Create a new branch (e.g. wcag22-contrast-technique)
• Duplicate techniques/general/G18.html to contrast-update.html
• Make the text changes.
• Create a PR from that branch.

[bruce-usab]

Thank you @alastc for that clear direction. My comment above was mostly to distill for myself the specifics of the discrepancy.

[alastc]

Sorry if I was 'process-splaining'! I'm just running through issue statuses and working out where things are.

[bruce-usab]

No, that was helpful!

[bruce-usab]

I have created PR #1223 using the correct threshold value.

[alastc]

Hi Andy,

That's just a WCAG 2.x update allowing for the use of the 'newer' value.

-Alastair