#!/bin/bash
# mk-compr - make a subdirectory of compressed images and videos based on current directory contents
# combines and adapts from my jpeg2sc, png2sc & conv-mstdn scripts
# Copyright 2010-2024 by Ian Kluft
# Redistribution permitted by the author under the conditions of the
# GNU General Public License Version 3.
#    https://opensource.org/licenses/GPL-3.0
#
# usage: mk-compr

# configuration
shopt -s nocasematch extglob

# globals
progname="$(basename "$0")"

# function: exit with error message
die()
{
    echo "$progname:" "$@" >&2
    exit 1
}

# function: check if destination file exists, return 0 as non-error to skip
skip_exists()
{
    dest=$1
    if [ -f "$dest" ]
    then
        echo "$dest exists - skipped"
        return 0
    fi
    return 1
}

# function: collect names of JPEG images
# uses null-delimited strings to read filenames with whitespace
find_jpeg()
{
    find -L .. -maxdepth 1 -type f -print0 -name '*.[Jj][Pp][Gg]' -o -name '*.[Jj][Pp][Ee][Gg]'
}

# function: collect names of PNG images
# uses null-delimited strings to read filenames with whitespace
find_png()
{
    find -L .. -maxdepth 1 -type f -print0 -name '*.[Pp][Nn][Gg]'
}

# function: collect names of mp4 videos
# uses null-delimited strings to read filenames with whitespace
find_mp4()
{
    find -L .. -maxdepth 1 -type f -print0 -name '*.[Mm][Pp]4'
}

# function: scale down JPEG images - adapted from jpeg2sc script
do_jpeg2sc()
{
    # process null-delimited strings with file names
    find_jpeg | while read -r -d "" infile
    do
        [ -f "$infile" ] || continue
        [[ "$infile" == *.jp?(e)g ]] || continue
        outfile="$(basename "${infile%.jp?(e)g}-sc.jpg")"

        echo "converting $infile to $outfile"
        skip_exists "$outfile" && continue
        jpegtopnm "$infile" | pnmcrop -sides -right | pnmgamma 1.3 | pamscale --height "${MED_SIZE:-1600}" | pnmtojpeg -quality=90 > "$outfile"
        exiftool -overwrite_original_in_place -tagsFromFile "$infile" "$outfile"
        echo
    done
}

# function: scale down PNG image - adapted from png2sc script
do_png2sc()
{
    find_png | while read -r -d "" infile
    do
        [ -f "$infile" ] || continue
        [[ "$infile" == *.png ]] || continue
        outfile="$(basename "${infile%.png}-sc.png")"

        echo "converting $infile to $outfile"
        skip_exists "$outfile" && continue
        pngtopnm "$infile" | pnmcrop -sides -right | pnmgamma 1.3 | pamscale --height "${MED_SIZE:-1600}" | pnmtopng -compression=9 > "$outfile"
        echo
    done
}

# function: compress MP4 videos - adapted from conv-mstdn script
do_compr_mp4()
{
    find_mp4 | while read -r -d "" infile
    do
        [ -f "$infile" ] || continue
        [[ "$infile" == *.mp4 ]] || continue
        outfile="$(basename "${infile%.mp4}.mstdn.mp4")"

        echo "converting $infile to $outfile"
        skip_exists "$outfile" && continue
        ffmpeg -i "$infile" -y -map 0:v -map 0:a -c:v libx264 -c:a copy -s 1280x720 -fs "40800KB" -vtag avc1 -crf 24 "$outfile" < /dev/null
        echo
    done
}

# mainline
mkdir -p compressed || die "failed to create subdirectory"
cd compressed || die "failed to enter subdirectory"
do_jpeg2sc
do_png2sc
do_compr_mp4