Make a basic macOS dynamic wallpaper

make-dynamic-wallpaper.sh

#!/bin/sh
# A script version of the instructions here: https://remove.codes/01-dynamic-wallpaper

set -e

# Helper functions.

verbose() {
  echo >&2
  echo $ "$@" >&2
  "$@"
}

usage() {
  echo "Usage: $0 <light_mode_image> <dark_mode_image> <output_image>"
  echo "Creates a dynamic wallpaper from two images."
}

# Check that the args are valid, and calculate file paths.

SRC_LIGHT="$1"
SRC_DARK="$2"
OUT="$3"

if [ -z "$SRC_LIGHT" ] || [ -z "$SRC_DARK" ] || [ -z "$OUT" ]; then
  usage
  exit 1
fi

EXT="${SRC_LIGHT##*.}"
if [ "$EXT" != "${SRC_DARK##*.}" ]; then
  echo "Error: The two images must have the same file extension."
  exit 1
fi

DIR="make-dynamic-wallpaper.inprogress"
DST_LIGHT=$DIR/light-mode.$EXT
DST_LIGHT_XMP=$DIR/light-mode.xmp
DST_DARK=$DIR/dark-mode.$EXT

# Install dependencies.

brew list "libheif" "exiv2" >/dev/null || verbose brew install "libheif" "exiv2"

# Write and copy all necessary files.

verbose mkdir "$DIR"
verbose cp "$SRC_LIGHT" "$DST_LIGHT"
verbose cp "$SRC_DARK" "$DST_DARK"
verbose cat <<EOF >"$DST_LIGHT_XMP"
<?xpacket?>
<x:xmpmeta xmlns:x="adobe:ns:meta">
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns">
<rdf:Description xmlns:apple_desktop="http://ns.apple.com/namespace/1.0"
apple_desktop:apr=
"YnBsaXN0MDDSAQMCBFFsEAFRZBAACA0TEQ/REMOVE/8BAQAAAAAAAAAFAAAAAAAAAAAAAAAAAAAAFQ=="/>
</rdf:RDF>
</x:xmpmeta>
EOF

# Do the conversions.

verbose exiv2 -i X in "$DST_LIGHT"

if [ "$(echo "$EXT" | tr '[:upper:]' '[:lower:]')" = "png" ]; then
  verbose heif-enc -L "$DST_LIGHT" "$DST_DARK" -o "$OUT"
else
  verbose heif-enc "$DST_LIGHT" "$DST_DARK" -o "$OUT"
fi

# Clean up.

verbose rm -rf "$DIR"