Command line

Homebrew links undertone onto your PATH; it is also at Undertone.app/Contents/Helpers/undertone. It starts in milliseconds and needs no permission.

A new picture now, as Shuffle in the menu. Undertone must be running. For a hotkey, with skhd:

lcmd + alt - w : undertone shuffle

Draws one picture to a file, without the app and without touching the desktop:

undertone render --style silk --tonality dusk --appearance light --seed 9 -o silk.png
Option Default
--style mesh See undertone styles.
--tonality ember See undertone tonalities.
--appearance dark dark or light.
--seed 1 Any whole number; the same seed draws the same picture.
--grain 0.035 0 for none.
--vignette 1 0 for none.
--effect none Turns an effect on at its defaults; give it more than once for more. See undertone effects.
--size 3024x1964 In pixels (a 14-inch MacBook Pro).
--scale 2 Pixels to a point: grain, lines and text follow points.
--strip 0 A black strip across the top, in points (37 is a notched MacBook's menu bar).
--corners 0 Rounded corners below the strip, in points.
--title, --subtitle none Centred text.
-o required The file; .jpg writes a JPEG, anything else a PNG.

Every image in these docs was drawn this way, or by the app from the same renderer.

The same picture in motion, written as a movie: one seamless loop, then a settle that slows it to a stop on the still picture. It takes every render option, and:

Option Default
--seconds 12 The loop's length.
--fps 30 Frames per second.
--settle 2.5 The settle's length in seconds; 0 for none.
--movement 1 How far things move; 0.5 is subtle, 1.6 strong.
--easing easeOut glide, easeOut or spring.
--codec hevc hevc or h264. 
undertone movie --style aurora --tonality aurora --size 1920x1080 --scale 1 -o aurora.mp4

undertone config prints where the config file is; --defaults prints every setting at its default; --check [file] lists what Undertone cannot use in it, by line, and exits with 1 if there is anything.

List the names render takes, styles with a line on each.

The version, build number and commit of the app it belongs to.