Preview

The preview command shows the resolved palette families and semantic tokens for a seed color and template without writing any files. It is a quick way to inspect what colors a particular seed and template combination produces before committing to a full generate run.

Usage

chromasync preview --seed "#ff6b6b" --template brutalist

Preview prints a plain-text summary to stdout and exits. No targets are invoked and no files are created.

Options

Flag	Required	Default	Description
`--seed`	yes	—	Seed color in `#RRGGBB` format
`--template`	yes	—	Template name or path to a template TOML file
`--mode`	no	`dark`	Theme mode: `dark` or `light`
`--contrast`	no	`relative-luminance`	Contrast heuristic: `relative-luminance` or `apca-experimental`

The --template flag accepts the same values as in generate — a built-in template name, a user-config template name, or a file path.

Output format

The output has three sections: a header with generation parameters, a palette families block, and a semantic tokens block.

Seed: #ff6b6b
Mode: dark
Template: brutalist
Contrast: relative-luminance
Template Source: built-in (brutalist-dark.toml)
Description: High-contrast theme with louder borders and harder accent separation

The header shows the seed, mode, template name, contrast strategy, where the template was loaded from, and its description (if any).

Palette families

Palette Families
primary         hue=12.34 chroma=0.123  0=#111111 10=#1a1a1a 20=#222222 ...
secondary       hue=45.67 chroma=0.098  0=#111111 10=#1a1a1a 20=#222222 ...
neutral         hue=12.34 chroma=0.008  0=#111111 10=#1a1a1a 20=#222222 ...
...

Each row shows a palette family with its hue and chroma values, followed by tone samples rendered as hex colors. This lets you see the full color ramp available to template rules.

Semantic tokens

Semantic Tokens
bg              #1a1a1a
bg_secondary    #202020
surface         #252525
surface_elevated #2a2a2a
text            #e0e0e0
text_muted      #a0a0a0
border          #404040
border_strong   #505050
accent          #ff6b6b
accent_hover    #ff5555
accent_active   #ff4444
accent_fg       #ffffff
selection       #ff6b6b
link            #6b9bff
success         #6bff6b
warning         #ffff6b
error           #ff6b6b

All 17 resolved tokens are listed with their final hex values. These are the exact colors that targets would substitute into output files during generate.

Comparing templates

Preview is useful for comparing how different templates interpret the same seed:

chromasync preview --seed "#4ecdc4" --template minimal
chromasync preview --seed "#4ecdc4" --template brutalist
chromasync preview --seed "#4ecdc4" --template terminal

Comparing modes

Check how dark and light modes differ for the same seed and template:

chromasync preview --seed "#4ecdc4" --template minimal --mode dark
chromasync preview --seed "#4ecdc4" --template minimal --mode light

Contrast strategies

The --contrast flag controls how Chromasync ensures readable foreground colors. The default relative-luminance uses WCAG 2.x contrast ratio (minimum 4.5:1). The apca-experimental option uses the APCA algorithm instead. Preview shows which strategy was used in the header so you can verify the resolved tokens meet your accessibility requirements.

chromasync preview \
  --seed "#4ecdc4" \
  --template minimal \
  --contrast apca-experimental

See Contrast strategies for details on the available algorithms.

Preview vs generate

	preview	generate
Output	Text to stdout	Files to disk
Targets	Not used	Required (`--targets`)
Output directory	Not used	Required (`--output`)
Purpose	Inspect colors	Create theme files

Both commands use the same palette generation and token resolution pipeline, so the colors shown by preview are exactly what generate would produce.

Keyboard shortcuts

Chromasync