IN=./onchain
OUT=./base64
PREFIX='data:image/octet-stream;base64,'

mkdir -p "$OUT"
for f in "$IN"/*.avif; do
  b=$(basename "${f%.*}")
  { printf '%s' "$PREFIX"; base64 < "$f" | tr -d '\n'; } > "$OUT/$b.txt"
  printf '%-24s %9d B -> %9d B  x%.4f\n' "$b" \
    "$(wc -c <"$f")" "$(wc -c <"$OUT/$b.txt")" \
    "$(echo "scale=6;$(wc -c <"$OUT/$b.txt")/$(wc -c <"$f")"|bc)"
done

echo "--- verifying round trip ---"
for f in "$IN"/*.avif; do
  b=$(basename "${f%.*}")
  if sed "s|^$PREFIX||" "$OUT/$b.txt" | base64 -d | cmp -s - "$f"
    then echo "OK       $b"
    else echo "MISMATCH $b"
  fi
done