mkgif

#!/bin/bash

# Generates an animated GIF from a source video (e.g. a .mov file)
# See:
# * http://superuser.com/questions/556029/how-do-i-convert-a-video-to-gif-using-ffmpeg-with-reasonable-quality
# * http://blog.pkh.me/p/21-high-quality-gif-with-ffmpeg.html
# Requires ffmpeg on the PATH

# Usage:
# mkgif filename [output_width]

set -euo pipefail

inputfile=""
outputfile=""
vidwidth=640
palettegenMode="full"

function usage() {
  echo "Usage:"
  echo "  ${0##*/} [--width|-w <value>] [--output <file path>] [-d | --optimize-diff] inputFilePath"
}
first_arg=""
second_arg="${DEFAULT_SECOND_ARG:-}"
positional_args=()

while [[ $# -gt 0 ]]; do
  case "$1" in
  -w | --width)
    vidwidth="$2"
    shift
    ;;
  -o | --output)
    outputfile="$2"
    shift
    ;;
  -d | --optimize-diff)
    palettegenMode="diff"
    ;;
  --help | -h)
    usage
    exit 1
    ;;
  -* | --*)
    usage
    exit 1
    ;;
  *)
    positional_args+=("$1")
    ;;
  esac

  shift
done
set -- "${positional_args[@]}"

inputfile="$1"
if [[ -z "$inputfile" ]]; then
  echo "No filename specified!"
  usage
  exit 1
fi

if [[ ! -f "$inputfile" ]]; then
  echo "File $inputfile does not exist!"
  usage
  exit 1
fi

if [[ -z "$outputfile" ]]; then
  outputfile=${inputfile%.*}.gif
fi

echo "Generating the GIF as $outputfile (width = $vidwidth)..."
ffmpeg -i "$inputfile" -vf "fps=10,scale=$vidwidth:-1:flags=lanczos,split[s0][s1];[s0]palettegen=stats_mode=$palettegenMode[p];[s1][p]paletteuse" "$outputfile"
echo "Done!"