#!/bin/sh
#------------------------------------------------------------------------------
# =========                 |
# \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
#  \\    /   O peration     | Website:  https://openfoam.org
#   \\  /    A nd           | Copyright (C) 2015-2020 OpenFOAM Foundation
#    \\/     M anipulation  |
#------------------------------------------------------------------------------
# License
#     This file is part of OpenFOAM.
#
#     OpenFOAM is free software: you can redistribute it and/or modify it
#     under the terms of the GNU General Public License as published by
#     the Free Software Foundation, either version 3 of the License, or
#     (at your option) any later version.
#
#     OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
#     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
#     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
#     for more details.
#
#     You should have received a copy of the GNU General Public License
#     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
#
# Script
#     foamCreateVideo
#
# Description
#     Creates a video file from PNG images
#     - requires mencoder or ffmpeg
#
#------------------------------------------------------------------------------

usage() {
    cat <<USAGE

Usage: ${0##*/} [OPTIONS] ...
options:
  -dir   | -d <dir>   directory containing png images (default local dir)
  -fps   | -f <fps>   frames per second (default = 10)
  -help  | -h         print the usage
  -image | -i <name>  name of image sequence (default = image)
  -out   | -o <name>  name of output video file (default = video)
  -start | -s <frame> specify the start frame number for ffmpeg
  -webm  | -w         WebM output video file format

Creates a video file from a sequence of PNG images
- A sequence named "image" will expect files image.0000.png, image.0001.png, etc
- The default output video compression format is MPEG-4, with WebM as an option
- The default file name, using MPEG-4 compression, is video.mp4
- By default the video codec is high resolution

Requires mencoder or ffmpeg for MPEG-4 output, ffmpeg for WebM output

USAGE
}

error() {
    exec 1>&2
    while [ "$#" -ge 1 ]; do echo "$1"; shift; done
    usage
    exit 1
}

# Default settings
dir=.
image=image
video=video
fps=10
fmt=mp4
start=

while [ "$#" -gt 0 ]
do
   case "$1" in
   -h | -help)
      usage && exit 0
      ;;
   -d | -dir)
      [ "$#" -ge 2 ] || error "'$1' option requires an argument"
      dir=$2
      shift 2
      ;;
   -f | -fps)
      [ "$#" -ge 2 ] || error "'$1' option requires an argument"
      fps=$2
      shift 2
      ;;
   -i | -image)
      [ "$#" -ge 2 ] || error "'$1' option requires an argument"
      image=$2
      shift 2
      ;;
   -o | -out)
      [ "$#" -ge 2 ] || error "'$1' option requires an argument"
      video=$2
      shift 2
      ;;
   -s | -start)
      [ "$#" -ge 2 ] || error "'$1' option requires an argument"
      start=$2
      echo "Selected start frame, requires ffmpeg..."
      [ "$start" -eq "$start" ] 2> /dev/null || \
          error "'$1' option requires an integer argument"
      shift 2
      ;;
   -w | -webm)
      fmt=webm
      echo "Selected $fmt format, requires ffmpeg..."
      shift
      ;;
   -*)
      error "invalid option '$1'"
      ;;
   *)
      break
      ;;
    esac
done

ffmpegCreateVideo () {
    _dir="$1"
    _image="$2"
    _fps="$3"
    _out="$4"
    _fmt="$5"
    _start="$6"
    _pwd="$(pwd)"

    [ "$_start" ] && _start="-start_number $_start"

    cd "$_dir" || return 1

    #shellcheck disable=SC2086
    ffmpeg \
        -framerate "$_fps" \
        $_start \
        -i "$_image".%04d.png \
        -vf "format=yuv420p,pad=ceil(iw/2)*2:ceil(ih/2)*2" \
        "$_pwd/$_out.$_fmt"

    return 0
}

mencoderCreateVideo () {
    _dir="$1"
    _image="$2"
    _fps="$3"
    _out="$4"

    mencoder \
        "mf://$_dir/$_image.*.png" \
        -mf fps="$_fps" \
        -o "$_out.$_fmt" \
        -ovc x264

    return 0
}

isInstalled () {
    command -v "$1" >/dev/null 2>&1
}

#
# MAIN
#

[ -f "$(find "$dir" -name "$image.*.png" | sort | head -1)" ] || \
    error "Cannot find first file in image sequence"

! [ "$fmt" = "webm" ] && ! [ "$start" ] && isInstalled mencoder && \
    mencoderCreateVideo "$dir" "$image" "$fps" "$video" && \
    exit 0

isInstalled ffmpeg && \
    ffmpegCreateVideo "$dir" "$image" "$fps" "$video" "$fmt" "$start" || \
        echo "ffmpeg not installed."