Deep Dive: Weather Icon Colorization Pipeline

[ldmcclatchey]

I recently updated the weather demo with a new icon colorization pipeline, and
I wanted to share some of the technical details behind how it works.

Palette Extraction

The recolor engine analyzes each SVG icon and extracts a normalized palette
based on luminance buckets. This allows the system to classify each path into
roles (primary, secondary, highlight, shadow) regardless of the original icon
style.

Classification

Each path is run through a simple classifier that determines its semantic role
based on:

• relative brightness
• stroke vs fill
• contrast against neighboring paths
• structural hints in the SVG

This produces a stable mapping even across icons with different original
designs.

Recoloring

Once roles are assigned, the engine applies a theme palette. The demo currently
uses a light, neutral palette, but the system supports:

• dark mode palettes
• high‑contrast palettes
• custom theme packs
• per‑condition accent colors

Integration with the Demo

The demo loads the recolored icons directly from the generated output folder.
A versioned query string (?v=2) ensures browsers fetch the updated SVGs
instead of using cached versions.

Testing

The recolor engine includes:

• unit tests for palette extraction
• classifier tests
• integration tests validating full icon transforms
• fixture comparisons to ensure consistency

This keeps the output stable across updates.

If anyone is interested in extending the palette system or adding additional
themes, I’m open to ideas.