#!/bin/bash
#default values
#based on http://superuser.com/questions/556029/how-do-i-convert-a-video-to-gif-using-ffmpeg-with-reasonable-quality
fps=15
width=320

filename() {
    if [ ! -f "$1" ]; then return 1; fi
    filename1=$(basename "$1")
    filename1="${filename1%.*}"
    echo "$filename1"
}

numcomp() {
    #compare two floating point numbers
    #example: numcomp 2 -gt 3   - return status 1
    if [ "$#" -ne 3 ]; then echo "compare: wrong number of parameters" >&2; return 1; fi
    case "$2" in
    '-gt') op='>';;
    '-ge') op='>=';;
    '-lt') op='<';;
    '-le') op='<=';;
    *) echo "compare: wrong operator" >&2; exit 1 ;;
    esac
    output="$(echo "$1 $op $3" 2>&1 | bc -l 2>&1)"
    case "$output" in
    '0') return 1;;
    '1') return 0;;
    *) echo "compare error: $output"; exit 1;;
    esac
}

gengif() {
    if [ ! -f "$1" ]; then
    echo "$1 doesn't exists!" >&2
    return 1
    fi
    f_width="$(mediainfo '--Inform=Video;%Width%' "$1")"
    f_fps="$(mediainfo '--Inform=Video;%FrameRate%' "$1")"
    if [ "$fps" = 'auto' ] || [ "$fps" = '0' ]; then
    fps=$f_fps
    echo "fps value set to $fps - from source video"
    elif numcomp "$f_fps" -lt "$fps"; then
    echo "File fps [$f_fps] is lower than target fps [$fps]. Setting target fps to $f_fps ."
    fps="$f_fps"
    fi

    if [ "$width" = 'auto' ] || [ "$width" = '0' ]; then
    width=$f_width
    echo "Width value set to $width - from source video"
    elif [ "$f_width" -lt "$width" ]; then
    echo "File width [$f_width] is lower than target width [$width]. Setting target width to $f_width ."
    width="$f_width"
    fi
    output="$(filename "$1")-${width}p-${fps}fps.gif"
    if [ -f "$output" ]; then
    echo "$output already exists!" >&2
    exit 1
    fi
    palette="$(mktemp ./palette.XXXXXX.png)"
    echo "ffmpeg -y -i $1 -vf fps=$fps,scale=$width:-1:flags=lanczos,palettegen $palette"
    ffmpeg -y -i "$1" -vf fps=$fps,scale=$width:-1:flags=lanczos,palettegen "$palette"
    echo "ffmpeg -i $1 -i $palette -filter_complex fps=$fps,scale=$width:-1:flags=lanczos[x];[x][1:v]paletteuse $output"
    ffmpeg -i "$1" -i "$palette" -filter_complex \
       "fps=$fps,scale=$width:-1:flags=lanczos[x];[x][1:v]paletteuse" "$output"
    rm "$palette"
}

help() {
    echo "
 VIDEO TO GIF GENERATOR
 USAGE: $0 [-f FPS] [-w WIDTH] [-h] MOVIE1 [MOVIE2 ...]
 OPTIONS:
  -h       - print this help
  -f FPS   - output fps. Can be floatpoint. (default is $fps)
           '0' or 'auto' to set to source video fps
  -w WIDTH - output width (default is $width)
           '0' or 'auto' to set to sorce video width
 If provided fps or width is greater than in source video, then value from source video will be used.
"
    exit 0
}

if [ $# -eq 0 ]; then
    help
fi

while [ $# -gt 0 ]; do
    case "$1" in
    -f)  fps="$2"; shift;;
    -w)  width="$2"; shift;;
    -h)  help;;
    --)  shift; break;;
    -*)  help
        exit 1;;
    *)  break;;# terminate while loop
    esac
    shift
    # all command line switches are processed,
    # "$@" contains all file names
done

for k in "$@"; do
    gengif "$k"
done