#!/usr/bin/env bash

if [ $# -ne 3 ]; then
    echo -e "\033[31;1merror:\033[0m this script expects three arguments, the file, the starting time and the duration."
    exit 1
fi

if [ ! -f "$1" ]; then
    echo -e "\033[31;1merror:\033[0m couldn't open $1: no such file."
    exit
fi

palette_dir=$(mktemp -d)

ffmpeg -y -ss $2 -to $3 -i $1 \
    -vf fps=30,scale=320:-1:flags=lanczos,palettegen $palette_dir/palette.png > /dev/null 2>&1

ffmpeg -ss $2 -to $3 -i $1 -i $palette_dir/palette.png -filter_complex \
    "fps=30,scale=640:-1:flags=lanczos[x];[x][1:v]paletteuse" -y output.gif > /dev/null 2>&1

rm -rf $palette_dir