extract-frame

#!/bin/sh

# extract a frame froma a video as a png file

# script usage
usage()
{
# if argument passed to function echo it
[ -z "${1}" ] || echo "! ${1}"
# display help
echo "\
# extract a frame froma a video as a png file
https://trac.ffmpeg.org/wiki/Seeking

$(basename "$0") -i infile.(mp4|mov|mkv|m4v|webm) -s 00:00:00.000 -o outfile.png
-i infile.(mp4|mov|mkv|m4v)
-s 00:00:00.000    :optional argument # if option not provided defaults to 00:00:00
-o outfile.png     :optional agument # if option not provided defaults to infile-name-frame-date-time"
exit 2
}

# error messages
NOTFILE_ERR='not a file'
INVALID_OPT_ERR='Invalid option:'
REQ_ARG_ERR='requires an argument'
WRONG_ARGS_ERR='wrong number of arguments passed to script'
NOT_MEDIA_FILE_ERR='is not a media file'

# if script is run arguments pass and check the options with getopts,
# else display script usage and exit
[ $# -gt 0 ] || usage "${WRONG_ARGS_ERR}"

# timecode - match 00:00:00.000
timecode='^[0-9]\{2\}:[0-9]\{2\}:[0-9]\{2\}([.]\{1\}[0-9]\{1,3\})?$'

# getopts check and validate options
while getopts ':i:s:o:h' opt
do
  case ${opt} in
     i) infile="${OPTARG}"
	[ -f "${infile}" ] || usage "${infile} ${NOTFILE_ERR}";;
     s) seconds="${OPTARG}"
	expr "${seconds}" : "${timecode}" 1>/dev/null;;
     o) outfile="${OPTARG}";;
     h) usage;;
     \?) usage "${INVALID_OPT_ERR} ${OPTARG}" 1>&2;;
     :) usage "${INVALID_OPT_ERR} ${OPTARG} ${REQ_ARG_ERR}" 1>&2;;
  esac
done
shift $((OPTIND-1))

# infile, infile name
infile_nopath="${infile##*/}"
infile_name="${infile_nopath%.*}"

# file command check input file mime type
filetype="$(file --mime-type -b "${infile}")"

# video mimetypes
mov_mime='video/quicktime'
mkv_mime='video/x-matroska'
mp4_mime='video/mp4'
m4v_mime='video/x-m4v'
webm_mime='video/webm'

# outfile file recording destination
outfile_default="${infile_name}-frame-$(date +"%Y-%m-%d-%H-%M-%S").png"
seconds_default='00:00:00'

# image to video function
extract () {
  ffmpeg \
  -hide_banner \
  -stats -v panic \
  -ss "${seconds:=${seconds_default}}" \
  -i "${infile}" \
  -q:v 2 -f image2 \
  -vframes 1 \
  "${outfile:=${outfile_default}}"
}

# check the files mime type
case "${filetype}" in
    ${mov_mime}|${mkv_mime}|${mp4_mime}|${m4v_mime}|${webm_mime}) extract "${infile}";;
    *) usage "${infile} ${NOT_MEDIA_FILE_ERR}";;
esac