autoscreen

Automatically take screenshots at a random time every hour. Wayland only, using grim.

What you can change:

• frequency: OnCalendar value in systemd-service/autoscreen.timer
• directory from where autoscreen will be run: WorkingDirectory value in systemd-service/autoscreen.service
• directory where the screenshots will be stored: DESTINATION_DIR variable in autoscreen.sh (overridable at runtime with the AUTOSCREEN_DESTINATION_DIR environment variable)
• file name suffix: AUTOSCREEN_FILENAME_SUFFIX environment variable, inserted just before autoscreen.png (useful to tell machines/installations apart)
• output format: AUTOSCREEN_FORMAT environment variable — png (default), jpeg, ppm, webp, avif or jxl
• encoder quality: AUTOSCREEN_QUALITY environment variable, 0-100 (default 90, higher is better; ignored for png/ppm)

Requirements

• grim
• for webp / avif / jxl output: cwebp (libwebp), avifenc (libavif), cjxl (libjxl) respectively

Installation

git clone https://github.com/dbeley/autoscreen
cd autoscreen
chmod +x autoscreen.sh
cp systemd-service/* ~/.config/systemd/user
systemctl --user daemon-reload
systemctl --user enable --now autoscreen.timer
systemctl --user status autoscreen

Nix / NixOS

A flake is provided, exposing the package, an overlay and a Home Manager module.

Try it without installing:

nix run github:dbeley/autoscreen

Home Manager

Add the flake as an input:

# flake.nix
inputs.autoscreen.url = "github:dbeley/autoscreen";

Then import the module and enable the service:

{
  imports = [ inputs.autoscreen.homeModules.default ];

  services.autoscreen = {
    enable = true;
    # destinationDir = "%h/Nextcloud/07_Images/01_autoscreen";
    # filenameSuffix = "nixos_";
    # format = "png";    # png | jpeg | ppm | webp | avif | jxl
    # quality = 90;      # 0-100, higher is better (ignored for png/ppm)
    # onCalendar = "hourly";
    # randomizedDelaySec = 3600;
  };
}

Note: destinationDir uses the systemd %h specifier for the user's home directory instead of $HOME (systemd expands %h in Environment=, not $HOME).

Formats

A PNG of a 4K screenshot is large (several MB, more on detailed content such as games). The lossy formats are roughly an order of magnitude smaller:

format	relative size (4K content)	notes
png	100 % (baseline)	lossless, grim-native
jxl	~8–10 %	best perceived quality, grim cannot emit it
avif	~5–10 %	smallest, but visible artifacts on fine texture
webp	~10–40 %	broadest viewer support
jpeg	~9 % on photos, >100 % on flat UI	grim-native, but poor for screenshots

quality is passed straight to the encoder (grim -q, cwebp -q, avifenc -q, cjxl -q), so it means the same thing everywhere: higher is better, 100 is lossless for avif and jxl.

Package / overlay

# packages
nix build github:dbeley/autoscreen

# overlay
{
  inputs.autoscreen.url = "github:dbeley/autoscreen";
  nixpkgs.overlays = [ inputs.autoscreen.overlays.default ];
  # pkgs.autoscreen is then available
}