Script for pixel-perfect scaling of Pokémon sprites or other pixel art for use as Discord or Mastodon emotes

pokescale.sh

#!/bin/bash

if [ $# -lt 2 ]; then
    echo "usage: $0 <infile> <outfile>"
    echo "use TARGET environment variable to set target size (default: 128)"
    exit 1
fi

convert -trim +repage "$1" "$2"
read -r w h <<<"$(identify -format '%[fx:w] %[fx:h]' "$2")"

size=$(python3 <<EOF
d=max($w, $h)
print("{0}x{0}".format(d*(${TARGET:-128}//d)))
EOF
)

mogrify -sample "$size" "$2"
optipng -quiet "$2"