#!/bin/sh
#
# video-thumbnails: A simple shell script to generate video thumbnails/screencaps
#
# Author: rumia <https://github.com/rumia>
# License: WTFPL
#

function quit {
   rm -rf "$1"
   exit
}

function get_seconds {
   if [[ "$1" == *:* ]]; then
      local tm_rev="$(echo "$1" | rev)"
      local ss="$(echo "$tm_rev" | cut -d: -f1 | rev)"
      local mm="$(echo "$tm_rev" | cut -d: -f2 | rev)"
      local hh="$(echo "$tm_rev" | cut -d: -f3 | rev)"
      local hhmmss="$(printf "%02d:%02d:%02d" "${hh:-0}" "${mm:-0}" "${ss:-0}")"
      date +%s -d "1970-01-01 $hhmmss UTC"
   else
      echo $1
   fi
}

usage="Generate screencaps for a video

Usage: $(basename "$0") [options] video-filename [interval-in-seconds]

Options:
   -t w[xh]       Numbers of tile (default: 4)
   -q quality     Image quality (default: 98)
   -d n           Divisor for frame dimension (default: 2)
   -b color       Background color (default: white)
   -f font        Default font (default: Droid-Sans-Regular)
   -s size        Default text size (default: 15)
   -p position    Timestamp position (default: NorthWest)
   -c color       Timestamp color (default: rgba(255, 255, 255, 0.7))
   -o color       Timestamp outline color (default: rgba(0, 0, 0, 0.2))
   -w px          Timestamp outline width (default: 2)
   -F font        Header font (will use default font if not specified)
   -S size        Header text size (will use default text size if not specified)
   -P position    Header text position (default: NorthWest)
   -C color       Header text color (default: black)
   -B color       Header background color (the default is the color specified by -b)
   -k n           Skip n seconds before capturing
   -h             Display this help
"

text_font="Droid-Sans-Regular"
text_size=15
timestamp_color="rgba(255, 255, 255, 0.7)"
timestamp_offset="+10+5"
timestamp_position="NorthWest"
outline_color="rgba(0, 0, 0, 0.2)"
outline_width=2
quality=98
tile=4
dim_divisor=2
background="white"
skip_sec=0

while getopts ":b:f:s:c:p:o:w:q:t:d:F:S:P:B:C:k:h" opt; do
   case "$opt" in
      b) background="$OPTARG" ;;
      f) text_font="$OPTARG" ;;
      s) text_size="$OPTARG" ;;
      c) timestamp_color="$OPTARG" ;;
      p) timestamp_position="$OPTARG" ;;
      o) outline_color="$OPTARG" ;;
      w) outline_width="$OPTARG" ;;
      q) quality="$OPTARG" ;;
      t) tile="$OPTARG" ;;
      d) dim_divisor="$OPTARG" ;;
      F) header_font="$OPTARG" ;;
      S) header_text_size="$OPTARG" ;;
      P) header_position="$OPTARG" ;;
      C) header_color="$OPTARG" ;;
      B) header_background="$OPTARG" ;;
      k) skip_sec=$(get_seconds "$OPTARG") ;;
      h)
         echo "$usage"
         exit 0
         ;;
      :)
         echo "Option -$OPTARG requires a value" >&2
         exit 1
         ;;
   esac
done

shift $((OPTIND-1))

input="$1"
if [ "$input" = "" ]; then
   echo "$usage" >&2
   exit 1
fi

if [ ! -e "$input" ]; then
   echo "No such file: $input" >&2
   exit 1
fi

filesize="$(stat -c %s "$input")"
if [ ${filesize:-0} -lt 1 ]; then
   echo "Empty video" >&2
   exit 2
fi

if [ $filesize -ge 1024 ]; then
   if [ $filesize -gt 1073741824 ]; then
      suffix="G"
      fs_div=1073741824
   elif [ $filesize -ge 1048576 ]; then
      suffix="M"
      fs_div=1048576
   else
      suffix="K"
      fs_div=1024
   fi
   filesize_info="$filesize B ($(echo "scale=2; $filesize / $fs_div" | bc -l) ${suffix}iB)"
else
   filesize_info="$filesize B"
fi

input_basename="$(basename "$input")"
input_filename="${input_basename%.*}"

interval=${2:-50}
interval=$(get_seconds $interval)

if [ $interval -lt 1 ]; then
   interval=50
fi

info="$(ffmpeg -i "$input" 2>&1)"
duration="$(echo "$info" | grep Duration | sed -r 's/^\s*Duration: ([:0-9]+).*$/\1/')"
if [ "$duration" = "" -o "$duration" = "00:00:00" ]; then
   echo "Empty video" >&2
   exit 2
fi

total_seconds="$(date +%s -d "1970-01-01 $duration UTC")"
if [ $total_seconds -lt 1 ]; then
   echo "Empty video" >&2
   exit 2
elif [ $interval -ge $total_seconds ]; then
   echo "The interval must be less than total length of the video: total=$total_seconds interval=$interval" >&1
   exit 3
fi

ndigit=${#total_seconds}

dimension="$(echo "$info" | grep '^\s*Stream.*Video' | cut -d , -f 3 | sed -r 's/^\s*([0-9x]+).*$/\1/')"
width="$(echo "$dimension" | cut -d x -f 1)"
height="$(echo "$dimension" | cut -d x -f 2)"
thumb_width=$(( $width / $dim_divisor ))
thumb_height=$(( $height / $dim_divisor ))
thumb_geom="${thumb_width}x${thumb_height}"

temp_dir=$(mktemp -td vidthumbs.XXXXXX)
if [ $? -ne 0 ]; then
   echo "Unable to create temporary directory" >&2
   exit 4
fi

trap 'quit "$temp_dir"' EXIT SIGINT SIGTERM

printf "Generating thumbnails: " >&2
thumb_index=0
start_sec=$interval
if [ $skip_sec -gt 0 ]; then
   start_sec=$(( $start_sec + $skip_sec ))
fi

for (( i = $start_sec; i < $total_seconds ; i += $interval )); do
   hh=$(( ($i / 3600) % 24 ))
   mm=$(( ($i / 60) % 60 ))
   ss=$(( $i % 60 ))
   timestamp="$(printf "%02d:%02d:%02d" $hh $mm $ss)"
   frame_file="$temp_dir/.frame.jpg"
   ((thumb_index++))

   ffmpeg \
      -ss $i \
      -i "$input" \
      -s $thumb_geom \
      "$frame_file" \
      -r 1 \
      -vframes 1 \
      -qscale 1 \
      -an \
      -vcodec mjpeg > /dev/null 2>&1

   thumb_name="$(printf "%s/%0${ndigit}d.jpg" "$temp_dir" "$thumb_index")"

   convert \
      "$frame_file" \
      -gravity "$timestamp_position" \
      -font "$text_font" \
      -pointsize "$text_size" \
      -stroke "$outline_color" \
      -strokewidth $outline_width \
      -fill none \
      -annotate "$timestamp_offset" "$timestamp" \
      -stroke none \
      -fill "$timestamp_color" \
      -annotate "$timestamp_offset" "$timestamp" \
      -quality "$quality" \
      "$thumb_name"

   printf "\rGenerating thumbnails: %d image(s)" "$thumb_index" >&2
done

echo

if [ $thumb_index -lt 2 ]; then
   montage_file="$thumb_name"
   montage_width="$thumb_width"
else
   echo -n "Creating montage: " >&2
   montage_file="$temp_dir/.montage.jpg"
   montage "$temp_dir"/*.jpg -geometry $thumb_geom -tile "$tile" -background "$background" -quality "$quality" "$montage_file"

   montage_dimension="$(identify -format "%wx%h" "$montage_file")"
   montage_width="$(echo "$montage_dimension" | cut -d x -f 1)"
   printf " %s px @ %d tile(s) created.\n" "$montage_dimension" "$tile" >&2
fi

header="File Name: $input_basename
File Size: $filesize_info
$(echo "$info" | sed -rn 's/^\s+//;/^(Duration|Stream)/p')"

echo "Creating preview header..." >&2

header_file="$temp_dir/.header.gif"
convert \
   -size "$(( $montage_width - 10 ))x" \
   -background "${header_background:-$background}" \
   -font "${header_font:-$text_font}" \
   -pointsize "${header_text_size:-$text_size}" \
   -fill "${header_color:-black}" \
   -stroke none \
   -gravity "${header_position:-NorthWest}" \
   -bordercolor "${header_background:-$background}" \
   -border 5x5 \
   caption:"$header" \
   "$header_file"

output_filename="${3:-${input_filename}-preview.jpg}"
montage -mode concatenate -tile 1 "$header_file" "$montage_file" -background "$background" -quality "$quality" "$output_filename"
echo "Generated preview: $output_filename" >&2