Convert TGS to APNG for Signal

tgs2apng.sh

#!/bin/zsh
# Convert Telegram stickets (TGS) and probably any lottie animation to a highly compressed and compact
# APNG for Signal.
#
# Copyright (C) 2021 Oever González <software@notengobattery.com>
# Open source under the MIT license.

conversor() {
  WORKING_DIR=$(mktemp -d)
  for file in "$@"; do
    BASE_NAME=$(basename "$file")
    UNCOMPRESSED="$WORKING_DIR/$BASE_NAME.json"
    FRAME_DIR="$WORKING_DIR/$BASE_NAME"
    BASE_FILE="$WORKING_DIR/${BASE_NAME}"
    BASE_STRIP="$WORKING_DIR/${BASE_NAME}_strip.png"
    RES=${RES:-256}
    r=$(($RES*2))

    gunzip -c "$file" > "$UNCOMPRESSED" || return $?
    TGS_INFO=$(tgs2png -i "$UNCOMPRESSED") || return $?
    mkdir -p "$FRAME_DIR"

    FRAMES=$(print "$TGS_INFO" | awk -F'[ ,=]' '{print $5}')
    _FPS=$(print "$TGS_INFO" | awk -F'[ ,=]' '{print $8}')
    DURATION=$(print "$TGS_INFO" | awk -F'[ ,=]' '{print $11}')

    for ((frame=0; frame<$FRAMES; frame++)); do
      f=$(($frame+1))
      tgs2png -s $(($r*4))x0 -o $frame -n 1 "$UNCOMPRESSED" > "$FRAME_DIR/$f.png" &
    done
    wait

    ffmpeg -r $_FPS -i "$FRAME_DIR/%d.png" -vcodec apng -vf scale=${r}:-1:flags=neighbor:sws_dither=none \
     -r ${FPS:=20} -plays 0 "${BASE_FILE}.apng"
    apngdis "${BASE_FILE}.apng" -s &>/dev/null
    pngnq-s9 -L -Qn -T15 -n128 -e '.1.png' "$BASE_STRIP"
    mv "${BASE_FILE}_strip.1.png" "$BASE_STRIP"
    pngquant --nofs --strip --ext '.2.png' "$BASE_STRIP"
    ffmpeg -r $_FPS -i "${BASE_FILE}_strip.2.png" -vcodec png -vf scale=${RES}:-1:flags=area:sws_dither=none \
     -pix_fmt rgba -y "${BASE_FILE}_strip.png"; rm "${BASE_FILE}_strip.2.png"
    pngnq-s9 -L -Qn -T15 -n96 -e '.1.png' "$BASE_STRIP"
    mv "${BASE_FILE}_strip.1.png" "$BASE_STRIP"
    pngquant --posterize 4 --nofs --strip --ext '.2.png' "$BASE_STRIP"
    mv "${BASE_FILE}_strip.2.png" "$BASE_STRIP"
    TFRAMES=$(imgp -x 100% -w "$BASE_STRIP" | awk -F'[x ]' '/->.*x/{print $2/$1}')
    apngasm "${BASE_FILE}_result.apng" "$BASE_STRIP" 1 $FPS -vs$TFRAMES -z2 -i64
    BYTE_SIZE=$(stat -c "%s" "${BASE_FILE}_result.apng")
    FILE_SIZE=$(printf '%g' $(($BYTE_SIZE / 1024.0)))
    if (($FILE_SIZE>300.0)); then rm -r "$WORKING_DIR"; return 1; fi
    mv "${BASE_FILE}_result.apng" "$PWD/${BASE_NAME}.$RES.$FPS.apng" || return $?
    echo "${BYTE_SIZE}: $BASE_NAME ($FILE_SIZE k) => { Resolution: $RES ; FPS: $FPS ; }"
  done
  rm -r "$WORKING_DIR"
}

{{ conversor "$@"; } || \
   RES=224 conversor "$@"; } || \
   RES=208 conversor "$@";