sh-goodies/pngizer.sh

#!/bin/sh
# PNGizer: convert any file into PNG image and back
# Depends on mktemp, tar, gzip, ImageMagick and pngcrush
# Created by Luxferre in 2026, released into public domain

# Convert any raw data file to PNG
# Usage: pngize_raw $infile $pngfile
pngize_raw() {
  temp_ppm="$(mktemp)"
  # get raw input size 
  fsize=$(wc -c < "$1")
  # calculate image side length to fit everything
  sidelen=$(echo "scale=0;1 + sqrt($fsize / 3 + 1)" | bc -l)
  # how many trailing zero bytes we need 
  remlen=$((sidelen * sidelen * 3 - fsize))
  # shape the PPM file:
  # 1. header (PPM binary)
  printf 'P6\n%s %s\n255\n' $sidelen $sidelen > $temp_ppm
  # 2. body (raw file data)
  cat "$1" >> $temp_ppm
  # 3. trailing zero bytes
  for i in $(seq 1 $remlen); do printf '\x00' >> $temp_ppm; done
  # convert PPM to PNG and remove the temporary PPM
  magick ppm:$temp_ppm png:$ofile
  rm -f $temp_ppm
}

# extract any raw data file from PNG
# Usage: unpngize_raw $pngfile $outfile
unpngize_raw() {
  temp_ppm="$(mktemp)"
  # convert PNG to PPM (should be P6)
  magick png:$1 ppm:$temp_ppm
  # extract the raw body
  tail -n +4 $temp_ppm > $2
  # remove the temporary PPM
  rm -f $temp_ppm
}

# Convert any file or directory to PNG
pngize() {
  ofile="$2"
  [ -z "$2" ] && ofile="$1.png"
  temp_arch="$(mktemp)"
  # containerize the input 
  GZIP=-9 tar czvf $temp_arch "$1"
  # run the conversion
  pngize_raw $temp_arch $ofile
  rm -f $temp_arch
  # apply compression
  pngcrush -ow $ofile
}

# Extract the file or directory from PNG
unpngize() {
  temp_arch="$(mktemp)"
  unpngize_raw "$1" $temp_arch
  gzip -dcq $temp_arch | tar xvf -
  rm -f $temp_arch
}

# entry point

[ -z "$2" ] && echo 'No input file specified! Exiting...' && exit 1
if [ "$1" = "e" ]; then
  [ -z "$3" ] && echo "No output file specified! Using $2.png as output file"
  pngize "$2" "$3"
elif [ "$1" = "d" ]; then
  unpngize "$2"
else
  echo 'Invalid mode! Use e for encoding or d for decoding'
fi