Helpers to compress PNG images

crush

#!/bin/bash

command_exists() {
  type "$1" &> /dev/null
}

for X in "$@"; do
  if [ ${X: -4} == '.png' ]; then
    if command_exists zopflipng; then
      zopflipng "$X" "$X"
    else
      pngcrush -ow "$X"
    fi
  elif [ ${X: -4} == '.svg' ]; then
    svgo $X
  else
    echo "? $X" 1>&2
  fi

done

pcrush

#!/bin/bash

DIR=$(dirname "$0")

# TODO: probably only works on macOS
CPUS=$(sysctl -n hw.ncpu)
PROCS=$((CPUS / 2))  # run half as many tasks as CPUs

if [[ "$PROCS" == "0" ]]; then
  PROCS="1"
fi

echo "Using $PROCS tasks..."
printf '%s\0' "${@}" | xargs -0 -P $PROCS -n 1 -I % bash -c "${DIR}/crush \"%\""