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Color Extraction Algorithm

Aether uses a pure Go median-cut algorithm to extract 16 ANSI-compatible colors from any wallpaper.

How It Works

1. Image Sampling

The image is loaded and scaled to 300x300 (preserving aspect ratio) using bilinear interpolation. Pixels are then sampled for analysis.

2. Median-Cut Quantization

The sampled pixels are fed into a median-cut algorithm that recursively splits the color space along its longest axis, producing dominant color clusters. This is more accurate than histogram-based approaches for identifying perceptually distinct colors.

3. Palette Mode

The dominant colors are then processed through one of eight palette generators:

  • normal (default) - Balanced extraction
  • monochromatic - Single-hue variations
  • analogous - Adjacent colors on the color wheel
  • pastel - Soft, muted colors
  • material - Google Material-inspired
  • colorful - High saturation, vibrant
  • muted - Desaturated, subtle
  • bright - High brightness colors

4. ANSI Color Mapping

Colors are mapped to the 16-color ANSI palette:

Index Role Description
0 Background Darkest color (light mode: lightest)
1 Red Hue ~0 degrees
2 Green Hue ~120 degrees
3 Yellow Hue ~60 degrees
4 Blue Hue ~240 degrees
5 Magenta Hue ~300 degrees
6 Cyan Hue ~180 degrees
7 White Light gray
8-14 Bright variants Boosted lightness and saturation
15 Bright White Brightest color (light mode: darkest)

5. Readability Normalization

Colors are adjusted to ensure readability against the background.

Light vs Dark Mode

Toggle light mode to swap darkest/lightest anchors:

  • Dark mode: color0 = darkest, color15 = lightest
  • Light mode: color0 = lightest, color15 = darkest

Caching

Extracted palettes are cached at ~/.cache/aether/color-cache/:

  • Cache key = MD5(path + mtime + mode)
  • Instant re-extraction for unchanged images
  • Editing a wallpaper in the Wallpaper Editor bypasses cache

Color Adjustments

After extraction, fine-tune with 12 adjustment sliders:

Saturation and Vibrance

Adjustment Range Effect
Vibrance -50 to +50 Intelligently boosts muted colors without over-saturating vivid ones
Saturation -100 to +100 Uniformly increases/decreases color intensity

Tone and Exposure

Adjustment Range Effect
Contrast -30 to +30 Difference between light and dark colors
Brightness -30 to +30 Overall lightness shift
Shadows -50 to +50 Dark tones only
Highlights -50 to +50 Bright tones only
Gamma 0.5 to 2.0 Non-linear brightness curve

Levels

Adjustment Range Effect
Black Point -30 to +30 Adjusts the darkest point
White Point -30 to +30 Adjusts the brightest point

Color Grading

Adjustment Range Effect
Hue Shift -180 to +180 degrees Rotates all colors around the color wheel
Temperature -50 to +50 Warm (orange/yellow) to cool (blue) shift
Tint -50 to +50 Green to magenta shift

Tips

  • Double-click any slider to reset it to default
  • Click on the value label to type a precise number
  • Use Reset Adjustments button to reset all sliders at once
  • Adjustments are saved with blueprints and restored when loading