Mpv - Taking screenshots of a movie file

#!/bin/bash
set -e
# Description: Take screenshots from video file using mpv.
script_name=$(basename "$0")
 
num_of_screenshots=$1
video_file=$2
 
# Error handling.
  usage_example="   e.g.: ${script_name} num_of_screenshot video_file"
 
  is_number_regex='^[0-9]+$'
  if ! [[ "${num_of_screenshots}" =~ ${is_number_regex} ]] ; then
    echo "Error: ${num_of_screenshots} is not a number. Aborted!"
    echo "${usage_example}"
    exit 1;
  fi
 
  if [ ! -f "${video_file}" ]; then
    echo "Error: ${video_file} is not file. Aborted!"
    echo "${usage_example}"
    exit 1;
  fi
 
# Take screenshots.
  increment=$(perl -E "say 98/${num_of_screenshots}")
  padding_size=$(echo -n "${num_of_screenshots}" | wc -m)
 
  position=${increment}
  for ((i=0; i < num_of_screenshots ; i++)); do
    printf -v position_format "%0${padding_size}d" ${i}  # Zero padding.
    output_file="${video_file}_${position_format}".ms.jpg
    mpv "${video_file}" --no-terminal --no-audio --vo=image --start=${position}% --frames=1  -o "${output_file}"
    echo "${output_file} created."
 
    position=$(perl -E "say ${position} + ${increment}")
  done