GoogleChromeLabs/squoosh

Reduce palette - alpha only

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#819 opened on Sep 5, 2020

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good first issuehelp wanted

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

Tech stack
typescriptweb components
Domain
frontendtooling
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.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
TypeScriptimage processing concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Start by examining the existing palette reduction implementation, likely in the Squoosh codebase under 'src/features/processors/palette reduction.ts' or similar. Understand how the current reduction works on RGBA channels, then design a toggle to restrict reduction to the alpha channel only. Review comments in issue #819 for any previous suggestions or considerations. The implementation should involve adding a checkbox or switch in the UI and passing a flag to the processing logic.
Reduce palette - alpha only · GoogleChromeLabs/squoosh#819 | Good First Issue