#!/bin/bash
function runffmpeg() {
    echo --------------------------------------------
    echo "ffmpeg" "$@"
    echo --------------------------------------------
    ffmpeg -hide_banner "$@"
}

# color curves
function curves() { echo -n "colorbalance=$1:$1:$1:$2:$2:$2:$3:$3:$3"; }
# scale videos with sar≠1 to have given width and pixel size 1x1
function SARscale() { echo -n "scale=trunc($1/2)*2:trunc((ih*$1)/(iw*sar*2))*2,setsar=1"; }
# usage: scale <width> [<height>]
function scale() { [ -n "$2" ] && echo -n "scale=$1:$2" || scale $1 -1; }
function fps() { [ -n "$1" ] && echo -n "fps=$1,"; }

function print_vars() {
    echo "w            = $w"
    echo "cropw        = $cropw"
    echo "croph        = $croph"
    echo "cropx        = $cropx"
    echo "cropy        = $cropy"
    echo "colors       = $colors"
    echo "fps          = $fps"
    echo "ss           = $ss"
    echo "d            = $d"
    echo "dither       = $dither"
    echo "bayer_scale  = $bayer_scale"
    echo "out          = $out"
    echo "curves       = $curves"
    echo "vidstab      = $vidstab"
    echo "vidstab_shakiness = $vidstab_shakiness"
    echo "vidstab_stepsize  = $vidstab_stepsize"
}

function print_help() {
    echo "converts video to gif"
    echo "usage: ${0##*/} [-y|-v|-h] [<file>]"
    echo ""
    echo "Options:"
    echo "  -y - automatically override the output file"
    echo "  -v - print user-set variables, final variables and then exit"
    echo "  -h - print help, user-set variables and exit"
    echo ""
    echo "The following enviroment variables can be set:"
    echo ""
    echo "  file - the file to convert, has to be defined or passed as an argument to the script"
    echo "  w - width, height is set to keep the aspect ratio, default: iw"
    echo "  cropx, cropy, cropw, croph - crop x/y (top left corner of crop) and with/height"
    echo "    defaults are 0/0, iw/ih"
    echo "  colors - the number of colors in gif, default: 50"
    echo "  fps - fps, default is empty string - keep fps of the source"
    echo "  ss - seek position, default: 0:00"
    echo "  d - duration, default: 5.0"
    echo "  out - filename of output (without extension), default: out"
    echo "  vidstab - 1 => use vidstab, not set by default"
    echo "  vidstab_shakiness - shakiness for vidstab, default: 8"
    echo "  vidstab_stepsize - step size for vidstab, default: 1"
    echo "  dither, bayer_scale - dithering method, and bayer scale (if dither == bayer)"
    echo "    default: bayer, 2"
    echo "  curves - applies colorbalance filter, is defined as 'a:b:c' where 0:0:0"
    echo "    is standard color balance with range -1 to 1 (the filter separates r/g/b,"
    echo "    this script doesn't)"
    echo ""
    echo "vars: "
    print_vars
    [ -z "$1" ] || exit "$1"
}

set -e
case "$1" in
    (-h*) print_help 0;;
    (-v) check_vars=1; shift;;
    (-y) y="-y"; shift;;
esac
[ $# -eq 0 ] || file="$1"
[ -n "$file" ] || print_help 1

echo "user set vars:"
print_vars

[ -n "$w"            ] || w=iw
[ -n "$cropw"        ] || cropw=iw
[ -n "$croph"        ] || croph=ih
[ -n "$cropx"        ] || cropx=0
[ -n "$cropy"        ] || cropy=0
[ -n "$colors"       ] || colors=50
[ -n "$fps"          ] || fps=''
[ -n "$ss"           ] || ss=0:00
[ -n "$d"            ] || d=5.0
[ -n "$vidstab"      ] || vidstab=''
[ -n "$dither"       ] || dither=bayer
[ -n "$bayer_scale"  ] || bayer_scale=2
[ -n "$out"          ] || out=out
[ -n "$vidstab_shakiness" ] || vidstab_shakiness=8
[ -n "$vidstab_stepsize"  ] || vidstab_stepsize=1
if [ -n "$curves" ]; then
    if [[ ! ( "$curves" =~ [0-9.]+:[0-9.]+:[0-9.]+ ) ]];then
        echo "Bad curves definition \'$curves' on line $LINENO"
        exit 1
    fi
    c1=${curves%%:*}
    c3=${curves##*:}
    ctmp=${curves#*:}
    c2=${ctmp%:*}
    curves_filter="$(curves $c1 $c2 $c3),"
fi

echo "final vars:"
print_vars
[ "$check_vars" != 1 ] || exit 0

crop="crop=$cropw:$croph:$cropx:$cropy"
filters="trim=duration=$d,$(fps $fps)${curves_filter}setpts=PTS-STARTPTS,$(SARscale iw),
    $(scale $w $h),$crop,format=yuv420p"
palette=/tmp/ffgif-$$-p.png

vidstab1="vidstabdetect=shakiness=$vidstab_shakiness:stepsize=$vidstab_stepsize"
vidstab2="vidstabtransform"

palettegen="palettegen=$colors:0:diff"
paletteuse="paletteuse=$dither:$bayer_scale"

if [ "$vidstab" != 1 ]; then
    runffmpeg -ss $ss -i "$file" -vf "$filters,$palettegen" $y "$palette"
    runffmpeg -ss $ss -i "$file" -i "$palette" \
        -lavfi "[0:v]$filters[x],[x][1:v]$paletteuse[o]" \
        -map [o] $y "${out}.gif"
    rm "$palette"
else
    tmpfile=/tmp/ffgif-$$-clip.mp4
    runffmpeg -ss $ss -i "$file" -t $d -b:v 2000k -vf "$filters" "$tmpfile"

    runffmpeg -i "$tmpfile" -vf "$palettegen" $y "$palette"
    runffmpeg -i "$tmpfile" -pass 1 -vf "$vidstab1" -f null -
    runffmpeg -i "$tmpfile" -i "$palette" -pass 2 \
        -lavfi "[0:v]$vidstab2[x],[x][1:v]$paletteuse[o]" \
        -map [o] $y "${out}.gif"
    rm "$tmpfile"
    rm "$palette"
fi