PaletteGuard — Palette Auditor for Aseprite

You picked a palette. Then you anti-aliased something, or pasted art in from another file, or ran it through a lossy round trip — and now there are colours in your sprite that are almost right.

You cannot see them. Your engine can. So can anyone who opens the file.

PaletteGuard finds every colour that is not in your palette and tells you exactly what it is, how many pixels it affects, and what it should be. Then it snaps them all — in one undo.

What it does

• Audit — lists every off-palette colour, sorted by how many pixels it covers, with the nearest palette entry and how far off it is
• Snap — rewrites those pixels to the nearest palette colour, whole sprite or active cel
• One undo — the entire fix is a single transaction, so Ctrl+Z takes all of it back
• Tolerance — treat near-misses as acceptable, or demand exact matches
• Transparent pixels are left alone: their RGB is meaningless and snapping them would invent edits

Nearest means nearest to the eye

Colour matching is weighted (green heaviest, blue lightest) rather than raw RGB distance. Unweighted matching picks visibly wrong targets — it will happily snap a mid-green to a blue that is the same arithmetic distance away. This does not.

Tested against real Aseprite

The matching core has a headless suite covering weighting, exact membership, tolerance, transparency handling and report ordering. On top of that, an end-to-end test runs real Aseprite in batch mode: it builds a sprite, dirties it with known off-palette pixels, asserts the audit finds exactly those, snaps them, verifies the actual pixel values afterwards, and checks that one undo restores every one of them.

Install

Double-click the .aseprite-extension file, or Edit → Preferences → Extensions → Add. Requires Aseprite 1.3+. Find it under Sprite → PaletteGuard: Audit Palette...

Transparency: PaletteGuard’s code is AI-assisted, disclosed via itch’s AI tagging. It generates no imagery — it only moves your pixels onto colours you already chose.