cwebpで指定したフォルダ内の画像を再圧縮する（ 非可逆 / ほぼロスレス / ロスレス モードはオプションで切り替え）

webp-convert.sh

#!/usr/bin/env bash

# エラーが発生した場合、およびパイプラインでエラーが発生した場合にスクリプトを終了する
set -e
set -o pipefail

# --- ヘルプメッセージ ---
usage() {
  cat <<EOF
Usage: $(basename "$0") [OPTIONS] <directory> <quality>

Converts all JPG/PNG files in a directory to WebP format.
Original files are moved to a subdirectory named '_original'.

Arguments:
  <directory>    The target directory containing JPG/PNG files.
  <quality>      The WebP quality level (0-100) or compression level (0-9) for lossless,
                 or near-lossless value (0-99) for near-lossless mode.

Options:
  -n, --dry-run       Show what would be done, without actually modifying any files.
  -l, --lossless      Use lossless compression (quality = compression level 0-9).
  -nl, --near-lossless Use near-lossless mode (quality = preprocessing 0-99).
  -h, --help          Display this help message and exit.

Modes:
  Default:        Lossy compression with quality 0-100
  --lossless:     Lossless compression with level 0-9 (0=fast, 9=best)
  --near-lossless: Near-lossless with preprocessing 0-99 (0=best quality)
EOF
  exit 1
}

# --- 初期値 ---
DRY_RUN=0
LOSSLESS=0
NEAR_LOSSLESS=0

# --- オプション解析 ---
while [[ $# -gt 0 ]]; do
  case "$1" in
    -n|--dry-run)
      DRY_RUN=1
      shift
      ;;
    -l|--lossless)
      LOSSLESS=1
      shift
      ;;
    -nl|--near-lossless)
      NEAR_LOSSLESS=1
      shift
      ;;
    -h|--help)
      usage
      ;;
    --)
      shift
      break
      ;;
    -*)
      echo "Unknown option: $1"
      usage
      ;;
    *)
      break
      ;;
  esac
done

# --- 引数のチェック ---
if [ "$#" -ne 2 ]; then
  echo "Error: Missing directory or quality argument."
  usage
fi

TARGET_DIR=$1
QUALITY=$2
CONVERT_DIR="$(dirname "$TARGET_DIR")/$(basename "$TARGET_DIR")_compressed"

# --- 依存関係のチェック ---
for cmd in cwebp find mv mkdir basename; do
  if ! command -v "$cmd" &> /dev/null; then
    echo "Error: Required command '$cmd' is not available in your PATH."
    if [ "$cmd" = "cwebp" ]; then
      echo "Please install WebP tools:"
      echo "  Ubuntu/Debian: sudo apt install webp"
      echo "  CentOS/RHEL:   sudo yum install libwebp-tools"
      echo "  macOS:         brew install webp"
      echo "  Arch Linux:    sudo pacman -S libwebp"
    fi
    exit 1
  fi
done

# --- 入力値の検証 ---
if [ ! -d "$TARGET_DIR" ]; then
  echo "Error: Directory '$TARGET_DIR' not found."
  exit 1
fi

# モードの排他チェック
mode_count=0
if [ "$LOSSLESS" -eq 1 ]; then mode_count=$((mode_count + 1)); fi
if [ "$NEAR_LOSSLESS" -eq 1 ]; then mode_count=$((mode_count + 1)); fi

if [ "$mode_count" -gt 1 ]; then
  echo "Error: Cannot use multiple compression modes simultaneously."
  exit 1
fi

# 品質値の検証
if [ "$LOSSLESS" -eq 1 ]; then
  if ! [[ "$QUALITY" =~ ^[0-9]+$ ]] || [ "$QUALITY" -lt 0 ] || [ "$QUALITY" -gt 9 ]; then
    echo "Error: Lossless compression level must be between 0 and 9."
    exit 1
  fi
elif [ "$NEAR_LOSSLESS" -eq 1 ]; then
  if ! [[ "$QUALITY" =~ ^[0-9]+$ ]] || [ "$QUALITY" -lt 0 ] || [ "$QUALITY" -gt 99 ]; then
    echo "Error: Near-lossless value must be between 0 and 99."
    exit 1
  fi
else
  if ! [[ "$QUALITY" =~ ^[0-9]+$ ]] || [ "$QUALITY" -lt 0 ] || [ "$QUALITY" -gt 100 ]; then
    echo "Error: Quality must be a number between 0 and 100."
    exit 1
  fi
fi

# --- ドライランの表示 ---
if [ "$DRY_RUN" -eq 1 ]; then
  echo "*** This is a DRY RUN. No files will be changed. ***"
  echo "----------------------------------------------------"
fi

echo "Target directory:     $TARGET_DIR"
if [ "$LOSSLESS" -eq 1 ]; then
  echo "Compression mode:     Lossless (level: $QUALITY)"
elif [ "$NEAR_LOSSLESS" -eq 1 ]; then
  echo "Compression mode:     Near-lossless (value: $QUALITY)"
else
  echo "Compression mode:     Lossy (quality: $QUALITY)"
fi
echo "Convert directory:     $CONVERT_DIR"
echo ""

# --- 処理の実行 ---
if [ "$DRY_RUN" -eq 0 ] ; then
  mkdir -p "$CONVERT_DIR"
fi

processed_files=0
# JPG/JPEG/PNG ファイルを検索
mapfile -t -d '' files < <(find "$TARGET_DIR" -type f \( -iname "*.jpg" -o -iname "*.jpeg" -o -iname "*.png" \) -print0)

for file in "${files[@]}"; do
  filename=$(basename "$file")
  # 拡張子を取得して webp に変更
  base_name="${filename%.*}"
  relative_path="${file#$TARGET_DIR/}"
  relative_dir=$(dirname "$relative_path")

  # 作業ファイルのパス
  convert_file="${CONVERT_DIR}/${relative_path}"
  working_dir=$(dirname "$convert_file")

  # WebP ファイルのパス
  webp_file="${working_dir}/${base_name}.webp"

  if [ "$DRY_RUN" -eq 1 ]; then
    if [ "$LOSSLESS" -eq 1 ]; then
      echo "[DRY RUN] Would convert '$file' to '$webp_file' (lossless level: $QUALITY)"
    elif [ "$NEAR_LOSSLESS" -eq 1 ]; then
      echo "[DRY RUN] Would convert '$file' to '$webp_file' (near-lossless: $QUALITY)"
    else
      echo "[DRY RUN] Would convert '$file' to '$webp_file' (quality: $QUALITY)"
    fi
    echo "[DRY RUN] Would move original to '$convert_file'"
  else
    echo "Processing: $relative_path"

    # WebP に変換
    if [ "$LOSSLESS" -eq 1 ]; then
      convert_cmd="cwebp -lossless -z $QUALITY"
      mode_desc="lossless level $QUALITY"
    elif [ "$NEAR_LOSSLESS" -eq 1 ]; then
      convert_cmd="cwebp -near_lossless $QUALITY -z 9"
      mode_desc="near-lossless $QUALITY"
    else
      convert_cmd="cwebp -q $QUALITY"
      mode_desc="quality $QUALITY"
    fi
    
    # 作業ディレクトリを作成
    if ! mkdir -p "$working_dir"; then
      echo "Error: Failed to create working directory '$working_dir'"
      continue
    fi

    if $convert_cmd "$file" -o "$webp_file" &>/dev/null; then
      echo "✓ Successfully converted: $relative_path → ${base_name}.webp ($mode_desc)"

    else
      echo "Error: Failed to convert '$file' to '$webp_file'"
      continue
    fi
  fi
  processed_files=$((processed_files + 1))
done

echo "----------------------------------------------------"
if [ "$processed_files" -eq 0 ]; then
  echo "No JPG/PNG files found to process."
else
  if [ "$DRY_RUN" -eq 1 ]; then
    echo "Dry run complete. Found $processed_files image file(s)."
  else
    echo "Successfully converted $processed_files image file(s) to WebP format."
  fi
fi