Simple bash script to convert MP4 videos to GIF

mp4-to-gif.sh

#!/bin/bash

#############################################
#
# mp4-to-gif
#
# Convert MP4 videos to GIF images
# Requires ffmpeg and imagemagick
#
# -g and --gifsicle options create a second optimised GIF for your consideration
# this obviously requires the gifsicle package
# http://www.lcdf.org/gifsicle/
#
# Add to PATH and alias for easy converting
# alias m2g='mp4-to-gif.sh'
#
# Author: Daniel Bennett
# License: BSD 3-Clause <https://opensource.org/licenses/BSD-3-Clause>
# Source: https://gist.github.com/Ultrabenosaurus/bbd4606ff444b4dc89c7e7b93b21c3ee
#
# Only tested on Windows 10 using the Ubuntu shell under Windows Subsystem for Linux
# I fully accept the possibility that this code is a demonstration of how not to code for bash
# but it works (for me)
#
#############################################

e=0

if [ $# -eq 0 ] || [ ! -f "`realpath "$1"`" ] ; then
    echo "No file specified for conversion!"
    echo "Usage: mp4-to-gif.sh path/to/video.mp4"
    e=1
fi
if [ "$(which ffmpeg)" = "" ] ; then
    if [ $e = 1 ] ; then
        echo ""
    fi
    echo "ffmpeg is required but not installed"
    e=1
fi
if [ "$(which convert)" = "" ] ; then
    if [ $e = 1 ] ; then
        echo ""
    fi
    echo "imagemagick is required but not installed!"
    e=1
fi
if [ $# -eq 2 ] ; then
    if [ $2 = "-g" ] || [ $2 = "--gifsicle" ] ; then
        if [ "$(which gifsicle)" = "" ] ; then
            if [ $e = 1 ] ; then
                echo ""
            fi
            echo "gifsicle is not installed - install it or stop using --gifsicle / -g options"
            e=1
        fi
    fi
fi
if [ $e = 1 ] ; then
    echo ""
    echo "Add to PATH for easy converting"
    echo "Add alias m2g='mp4-to-gif.sh' to your ~/.profile"
    echo ""
    echo "Only tested on Windows 10 using the Ubuntu shell under Windows Subsystem for Linux"
    exit 0
fi

n=$RANDOM
t="mp4-to-gif"
r=10
s=320
p=`realpath "$1"`
d=`dirname "$p"`
f=`basename "$p"`
f=${f%.*}

while [ -d "./$t-$n" ] ; do
    n=$RANDOM
done

mkdir -p ./$t-$n
ffmpeg -i "$p" -vf scale=$s:-1:flags=lanczos,fps=$r ./$t-$n/ffout%03d.png
convert -loop 0 ./$t-$n/ffout*.png "$d/$f.gif"
rm -r ./$t-$n
if [ $# -eq 2 ] ; then
    if [ $2 = "-g" ] || [ $2 = "--gifsicle" ] ; then
        gifsicle "$d/$f.gif" --colors 256 --optimize=3 > "$d/$f.g.gif"
    fi
fi

#############################################
# 
# Copyright 2019, Daniel Bennett
# 
# Redistribution and use in source and binary forms, with or without modification, are 
# permitted provided that the following conditions are met:
# 
# 1. Redistributions of source code must retain the above copyright notice, this list
#    of conditions and the following disclaimer.
# 
# 2. Redistributions in binary form must reproduce the above copyright notice, this
#    list of conditions and the following disclaimer in the documentation and/or other
#    materials provided with the distribution.
# 
# 3. Neither the name of the copyright holder nor the names of its contributors may be
#    used to endorse or promote products derived from this software without specific
#    prior written permission.
# 
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
# SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
# TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
# BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
# DAMAGE.
# 
# https://opensource.org/licenses/BSD-3-Clause
# 
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