This script takes videofile and converts it to high quality GIF, using ffmpeg.

hdgif.sh

#!/bin/bash
# Usage:
# hdgif -f='/path/to/video.mp4' -w=720 -q=2 -fps=22 -a=1
# -f = input video file
# -w = width of the final gif
# -q = quality, sets the bayer scale, lower number mean higher quality
# -fps = frames per second in the final gif
# -a = convert automatically, uses default options if not set and converts without asking
# -d = destination of where to save the final gif

show_bold() {
  echo -e "\033[1;34m$@\033[0m"
}

# declaring a couple of associative arrays
declare -A arguments=();  
declare -A variables=();
# declaring an index integer
declare -i index=1;
# any variables you want to use here
# on the left left side is argument label or key (entered at the command line along with it's value) 
# on the right side is the variable name the value of these arguments should be mapped to.
# (the examples above show how these are being passed into this script)
variables["-f"]="file";
variables["--file"]="file";
variables["-w"]="width";
variables["--width"]="width";
variables["-q"]="quality";
variables["--quality"]="quality";
#variables["-b"]="batch";
#variables["--batch"]="batch";
variables["-fps"]="fps";
variables["--fps"]="fps";
variables["-a"]="auto";
variables["--auto"]="auto";
variables["-d"]="destination";
variables["--dest"]="destination";
# $@ here represents all arguments passed in
for i in "$@"  
do
  arguments[$index]=$i;
  prev_index="$(expr $index - 1)";
  # this if block does something akin to "where $i contains ="
  # "%=*" here strips out everything from the = to the end of the argument leaving only the label
  if [[ $i == *"="* ]]
    then argument_label=${i%=*} 
    else argument_label=${arguments[$prev_index]}
  fi
  # this if block only evaluates to true if the argument label exists in the variables array
  if [ -n ${variables[$argument_label]} ]
    then
    # dynamically creating variables names using declare
    # "#$argument_label=" here strips out the label leaving only the value
    if [[ $i == *"="* ]]
      then declare ${variables[$argument_label]}=${i#$argument_label=} 
      else declare ${variables[$argument_label]}=${arguments[$index]}
    fi
  fi
  index=index+1;
done;

if [ -z "$file" ]; then
  show_bold "##"
  show_bold "## Input file not set, please provide basic setting."
  show_bold "## Usage example:"
  show_bold "## $ hdgif /some/path/to/file.mp4"
  show_bold "##"
  exit
fi

if [ -z $destination ]; then
  if [ -z $auto ]; then
    show_bold "##"
    show_bold "## Destination (./ by default):"
    read destination
    if [ -z $destination ]; then
      declare destination=./
    fi
  else
    if [ -z $destination ]; then
      declare destination=./
    fi
  fi
fi

if [ -z $fps ]; then
  if [ -z $auto ]; then
    show_bold "##"
    show_bold "## FPS (22 by default):"
    read fps
    if [ -z $fps ]; then
      declare fps=22
    fi
  else
    if [ -z $fps ]; then
      declare fps=22
    fi
  fi
fi

if [ -z $quality ]; then
  if [ -z $auto ]; then
    show_bold "##"
    show_bold "## Bayer scale (0-5, 3 by default):"
    read quality
    if [ -z $quality ]; then
      declare quality=3
    fi
  else
    if [ -z $quality ]; then
      declare quality=3
    fi
  fi
fi

if [ -z $width ]; then
  if [ -z $auto ]; then
    show_bold "##"
    show_bold "## Width (720 by default):"
    read width
    if [ -z $width ]; then
      declare width=720
    fi
  else
    if [ -z $width ]; then
      declare width=720
    fi
  fi
fi

dir=$(dirname "${file}")
parentdir=$(dirname "$dir")
filename=$(basename "${file}")
extension="${filename##*.}"
filename="${filename%.*}"
number=1
while [ -f $parentdir/gif/$filename"["$number-w$width-q$quality"].gif" ]
do (( number++ ))
done
outputpath=$parentdir/gif/$filename"["$number-w$width-q$quality"].gif"

touch $parentdir/gif/ || mkdir $parentdir/gif/
touch $parentdir/palette/ || mkdir $parentdir/palette/

echo
show_bold "##"
show_bold "## Convert video -> gif"
show_bold "## Path: $outputpath"
show_bold "## FPS: $fps"
show_bold "## Quality: $quality"
show_bold "## Width: $width"
show_bold "##"

do_convert() {
  # Filters and palette file
  palette="$parentdir/palette/$filename-palette.png"
  filters="fps=$fps,scale=$width:-1:flags=lanczos"
  # Generate palette
  # -v warning
  ffmpeg -i $file -pix_fmt yuvj422p -vf "$filters,palettegen=stats_mode=diff" -y $palette
  # MP4 to GIF
  # -v warning
  ffmpeg -i $file -pix_fmt yuvj422p -i $palette -lavfi "$filters [x]; [x][1:v] paletteuse=dither=bayer:bayer_scale=$quality" -y $outputpath
}

if [ -z $auto ]; then
  show_bold "##"
  show_bold "## Start Convert? [y/n]:"
  read startconvert
  if [ "$startconvert" == "y" ]; then
    do_convert
  fi
else
  do_convert
fi