#!/bin/bash

# install ffmpeg and gifsicle if not exists
which ffmpeg > /dev/null || brew install ffmpeg
which gifsicle > /dev/null || brew install gifsicle

usage () {
  echo "Usage:" 1>&2
  echo "  mov2gif [-d delay] [-o 1|2|3] [-r frame_rate] [-w width] input_file" 1>&2
  echo "" 1>&2
  echo "Example:" 1>&2
  echo "  mov2gif -w 640 -r 24 ~/Desktop/example.mov" 1>&2
  echo "" 1>&2
  echo "Options:" 1>&2
  echo "  -d delay   Set the delay between frames to time in hundredths of a second." 1>&2
  echo "  -o level   Optimize output GIF animations for space. Level determines how much optimization is done; higher levels take longer, but may have better results." 1>&2
  echo "  -r rate    Set frame rate." 1>&2
  echo "  -w width   Set width of output GIF." 1>&2
  exit 1
}

while getopts "d:o:r:w:h" opt
do
  case $opt in
    d) DELAY=$OPTARG ;;
    o) OPTIMIZE=$OPTARG ;;
    r) RATE=$OPTARG ;;
    w) WIDTH=$OPTARG ;;
    h) usage ;;
  esac
done

shift $((OPTIND - 1))
FILE=$1

if [ -z "$DELAY" ]; then
  DELAY=3
fi

if [ -z "$OPTIMIZE" ]; then
  OPTIMIZE=3
fi

if [ -z "$RATE" ]; then
  RATE=24
fi

if [ -z "$WIDTH" ]; then
  WIDTH=640
fi

if [ -z "$FILE" ]; then
  echo "Please specify input file path." 1>&2
  echo "" 1>&2
  usage
fi

# Split frames into gifs with `ffmpeg` and then combine them into an animated gif with `gifsicle`
ffmpeg -i "$FILE" -vf scale=$WIDTH:-1 -r $RATE -f gif - | gifsicle --optimize=$OPTIMIZE --delay=$DELAY -o "$FILE.gif"

echo "" 1>&2
echo "generated $(cd $(dirname "$FILE.gif"); pwd)/$(basename "$FILE.gif")" 1>&2

# I like to check generated gif in a browser (with Chrome)
open -a 'Google Chrome.app' "$FILE.gif"