png2jpg-ffmpeg-low.sh (tags:util,image,cli) (about: Optionless png2jpg-ffmpeg variant for low quality output)

png2jpg-ffmpeg-low.sh

#!/usr/bin/env bash
set -euo pipefail

Q=20

TEMP_DIR=""
DOWNLOADED_FFMPEG=false

cleanup() {
  if [ "$DOWNLOADED_FFMPEG" = true ] && [ -n "$TEMP_DIR" ]; then
    rm -rf "$TEMP_DIR"
  fi
}
trap cleanup EXIT

download_file() {
  local url="$1"
  local out="$2"

  if command -v curl >/dev/null 2>&1; then
    curl -L "$url" -o "$out"
  elif command -v wget >/dev/null 2>&1; then
    wget "$url" -O "$out"
  else
    echo "Error: Neither curl nor wget is available."
    exit 1
  fi
}

extract_archive() {
  local archive="$1"
  local dest="$2"

  case "$archive" in
    *.zip)
      command -v unzip >/dev/null 2>&1 || { echo "Error: unzip is required."; exit 1; }
      unzip -q "$archive" -d "$dest"
      ;;
    *.tar.xz)
      tar -xJf "$archive" -C "$dest"
      ;;
    *)
      echo "Error: Unsupported archive: $archive"
      exit 1
      ;;
  esac
}

FFMPEG_BIN="ffmpeg"

if ! command -v ffmpeg >/dev/null 2>&1; then
  echo ""
  echo "⚠️ ffmpeg not found. Temporarily downloading portable ffmpeg..."
  echo ""

  TEMP_DIR="$(mktemp -d)"
  DOWNLOADED_FFMPEG=true

  OS="$(uname -s)"
  ARCH="$(uname -m)"

  case "$OS" in
    Darwin)
      case "$ARCH" in
        arm64)
          FFMPEG_URL="https://ffmpeg.martin-riedl.de/redirect/latest/macos/arm64/release/ffmpeg.zip"
          ;;
        x86_64)
          FFMPEG_URL="https://ffmpeg.martin-riedl.de/redirect/latest/macos/amd64/release/ffmpeg.zip"
          ;;
        *)
          echo "Error: Unsupported macOS architecture: $ARCH"
          exit 1
          ;;
      esac
      ARCHIVE_FILE="$TEMP_DIR/ffmpeg.zip"
      ;;

    Linux)
      case "$ARCH" in
        x86_64|amd64)
          FFMPEG_URL="https://johnvansickle.com/ffmpeg/releases/ffmpeg-release-amd64-static.tar.xz"
          ;;
        aarch64|arm64)
          FFMPEG_URL="https://johnvansickle.com/ffmpeg/releases/ffmpeg-release-arm64-static.tar.xz"
          ;;
        *)
          echo "Error: Unsupported Linux architecture: $ARCH"
          exit 1
          ;;
      esac
      ARCHIVE_FILE="$TEMP_DIR/ffmpeg.tar.xz"
      ;;

    MINGW*|MSYS*|CYGWIN*)
      FFMPEG_URL="https://www.gyan.dev/ffmpeg/builds/ffmpeg-release-essentials.zip"
      ARCHIVE_FILE="$TEMP_DIR/ffmpeg.zip"
      ;;

    *)
      echo "Error: Unsupported OS: $OS"
      exit 1
      ;;
  esac

  download_file "$FFMPEG_URL" "$ARCHIVE_FILE"

  echo "Extracting ffmpeg..."
  extract_archive "$ARCHIVE_FILE" "$TEMP_DIR"

  FFMPEG_BIN="$(find "$TEMP_DIR" -type f \( -name "ffmpeg" -o -name "ffmpeg.exe" \) | head -n 1)"

  if [ ! -f "$FFMPEG_BIN" ]; then
    echo "Error: Failed to locate ffmpeg executable."
    exit 1
  fi

  chmod +x "$FFMPEG_BIN"

  echo "Using temporary ffmpeg:"
  echo "$FFMPEG_BIN"
fi

shopt -s nullglob nocaseglob

FOUND=false

for file in *.png; do
  FOUND=true
  filename="${file%.*}"
  output="${filename}.jpg"

  echo ""
  echo "Converting:"
  echo "  Input : $file"
  echo "  Output: $output"

  "$FFMPEG_BIN" -loglevel error -y -i "$file" \
    -q:v "$Q" \
    -pix_fmt yuvj420p \
    "$output"
done

if [ "$FOUND" = false ]; then
  echo "No PNG files found in current directory."
  exit 0
fi

echo ""
echo "Done."