simple-image-gallery.sh

#!/bin/bash

if [ $# -lt 2 ]
then
  echo "Usage: $0 output inputs*"
  exit 1
fi

set -e

OUTPUT="$1"
shift

SIZE=256
TARGET="$(mktemp -d)"
TOTAL=$#
NPROCS="$(nproc)"

running_jobs() {
  jobs="\\j"
  echo -n "${jobs@P}"
}

waitjob() {
  wait -n || echo failed
  echo -en "\rThumbnail $completed of $TOTAL ...\e[K"
  let completed+=1
}

let completed=1

for INPUT in "$@"
do
  if [ $(running_jobs) -ge $NPROCS ]
  then
    waitjob
  fi

  convert -resize "${SIZE}x${SIZE}" "$INPUT" "$TARGET/${INPUT//\//-}" &
done

while [ $(running_jobs) -gt 0 ]
do
  waitjob
done

echo
echo Creating "$OUTPUT"
montage "$TARGET"/* "$OUTPUT"