GoogleChromeLabs/squoosh

Reduce palette - alpha only

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#819 opened on Sep 5, 2020

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good first issuehelp wanted

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Description

WebP and JPEG-XL encode alpha data 'losslessly'. I'm not 100% sure with JPEG-XL, but WebP's compression benefits from palette reduction.

It'd be good to add a toggle to palette reduction that makes it only act on the alpha channel of the image.

Contributor guide

Research direction
Investigate how WebP and JPEG XL handle alpha channel compression. Familiarize yourself with Squoosh's palette reduction code (likely in lib/codecs or processors). Implement a checkbox or toggle that applies palette reduction only to the alpha channel. Test with images containing transparency to verify compression benefits.
Tech stack
typescript
Domain
frontend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
TypeScriptImage compression fundamentals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65