A theme from your wallpaper

Take every colour of the shell from your wallpaper, and follow it when the wallpaper changes. Strand reads the picture, builds a Material 3 palette from it, and springs every colour on screen to the new palette. For the whole theme file, with token sets and a look switcher, see the guide's level 5.

#The files

// theme.strand: the palette comes from the wallpaper
state prefs from "prefs.toml" {
  wallpaper: path = "~/Pictures/wall.jpg"; accent: color = #7aa2f7
}
let scheme: Palette = material(image: prefs.wallpaper, dark: system.dark)
                      ?? material(seed: prefs.accent, dark: system.dark)   // until the picture is read
use palette scheme
file "~/.cache/strand/accent.txt" { text: $accent }   // kept in step with every switch

A bar to see it on:

bar Top {
  edge: top; height: 32
  bg: $surface; font: $font.ui; color: $fg
  split { pad: 0, $space.3
    start { box { size: 12; radius: full; bg: $accent } }
    center { text clock.format("%H:%M") }
    end { text pct(battery.percent) { color: $fg.muted } }
  }
}

Point the setting at your wallpaper. prefs.toml is in your config directory and is plain TOML; Strand makes it the first time a value is written:

wallpaper = "~/Pictures/mountains.jpg"

or, from a terminal or a wallpaper script:

strand set prefs.wallpaper ~/Pictures/mountains.jpg

Here the bar starts in a purple picture's colours; then the setting points at another picture, and every colour springs to its palette:

#How it works

• material(image: …) builds a palette from a picture. It quantises a 128 px downscale of the image away from the logic thread, and caches the result by the file's content, so the same picture is not quantised twice.
• It is an Async. Reading the picture takes a moment, so its value is not there at first. ?? material(seed: …) is the palette to use until it is. While a new picture is read the old palette holds, so the screen never flashes other colours.
• The file is watched, and so is the target of a link to it. A script that writes a new picture over it, or swaps the link, re-themes the shell; so does pointing prefs.wallpaper at another file.
• use palette scheme makes it the palette in force. With no tokens of your own, the built-in spacing, radii, fonts and springs stay as they are.
• The last palette is kept across restarts, so the shell starts in your wallpaper's colours rather than the default ones.
• dark: system.dark follows your desktop's light or dark setting.

When the palette changes, the colours spring to the new one in OKLab, and the shell's state stays as it was: an open launcher keeps its query. Tokens and theming says how a swap animates.

#Your colours for other programs

The file line writes your accent to ~/.cache/strand/accent.txt as #rrggbb and rewrites it after every switch, once, with the new palette's value. A file with a template: writes a whole stylesheet or config; strand export writes the palette once:

strand export json                                   # the palette as data
strand export base24 -o ~/.cache/strand/base24.yaml  # for base16/base24 templates

Strand ships no per-app themes or templates: these are generic outputs, and the community's base16 and base24 templates work with the base24 export. The guide's level 5 writes a CSS file.

#Variations

• Another flavour of palette. material(image: …, variant: vibrant) picks another Material 3 scheme: tonal_spot (the default), vibrant, expressive, neutral, monochrome, fidelity, content, rainbow or fruit_salad.
• More contrast. contrast: system.contrast follows the desktop's contrast preference, 0 for normal and 1 for high.
• A published scheme instead. import("catppuccin:mocha") is a palette too, and so are base16 and base24 schemes, matugen output and W3C design-token files.