Python compresses website images in batches to slim down the website!

My website loads very slowly because the images are too large.

So, I thought about using Python to compress images.

Convert PNG files to WebP format – reduce file size by 88% directly!

The compression ratio is very high yet the image remains clear – a 1.4GB PNG file is compressed to just 120MB – and it's also in high resolution! Does anyone else have something like this?!

Python script functionality:

1. Recursive traversal uploads All files in the directory.

2. skip Files with a size of ≤ 300 KB.

3. Detect real image format(Identified by the file header, not the file extension); if the file is already in WebP format, it is skipped.

4. support  PNG、JPG、JPEG、BMP、TIFF Convert images to WebP format, with quality set to ; 85(adjustable).

5. Keep the original file name and extension unchanged.(For example; example.png Still; example.pngHowever, the content is WebP).

6. Back up the original file Copy to the specified backup directory (keep the complete relative path).

7. Skip non-image files (e.g.,  ); .zip、.pdf、.txt   etc.).

Python code:

import os
import shutil
from PIL import Image

# ---------- 配置 ----------
SOURCE_DIR = r"Z:\path\to\your\uploads"  # 替换为你的 uploads 目录路径
BACKUP_DIR = r"Z:\path\to\backup\uploads"  # 备份目录（原文件移动到这里）
QUALITY = 85  # WebP 压缩质量 (1-100)
SIZE_THRESHOLD = 300 * 1024  # 300KB

# 支持的图片扩展名（即使扩展名不对，也会通过文件头检测）
IMAGE_EXTS = {'.png', '.jpg', '.jpeg', '.bmp', '.tiff', '.tif', '.webp'}

# ---------- 核心函数 ----------
def is_webp(filepath):
    """通过文件头判断是否为 WebP 格式"""
    with open(filepath, 'rb') as f:
        header = f.read(12)
    return header[:4] == b'RIFF' and header[8:12] == b'WEBP'

def compress_to_webp(src_path, dst_path, quality):
    """将图片压缩为 WebP 并保存到 dst_path（保持扩展名不变）"""
    with Image.open(src_path) as img:
        # 处理透明度：RGBA 保留，其他转 RGB
        if img.mode in ('RGBA', 'LA', 'P'):
            img = img.convert('RGBA')
        else:
            img = img.convert('RGB')
        # 保存为 WebP，但文件名扩展名不变（浏览器根据文件头识别）
        img.save(dst_path, 'WEBP', quality=quality, method=6)

# ---------- 主程序 ----------
def main():
    if not os.path.exists(SOURCE_DIR):
        print(f"❌ 源目录不存在：{SOURCE_DIR}")
        return

    os.makedirs(BACKUP_DIR, exist_ok=True)

    total_files = 0
    processed = 0
    skipped_webp = 0
    skipped_small = 0
    skipped_nonimage = 0
    errors = []

    for root, dirs, files in os.walk(SOURCE_DIR):
        for filename in files:
            filepath = os.path.join(root, filename)
            total_files += 1

            # 1. 检查文件大小
            if os.path.getsize(filepath) <= SIZE_THRESHOLD:
                skipped_small += 1
                continue

            # 2. 检查是否为支持的图片格式（扩展名初步过滤）
            ext = os.path.splitext(filename)[1].lower()
            if ext not in IMAGE_EXTS:
                skipped_nonimage += 1
                continue

            # 3. 真实格式检测（优先检测是否为 WebP）
            try:
                real_format = Image.open(filepath).format
            except Exception:
                # 无法打开则跳过
                skipped_nonimage += 1
                continue

            # 如果已经是 WebP，跳过
            if real_format == 'WEBP':
                skipped_webp += 1
                continue

            # 4. 准备备份路径（保留相对路径）
            rel_path = os.path.relpath(filepath, SOURCE_DIR)
            backup_path = os.path.join(BACKUP_DIR, rel_path)
            os.makedirs(os.path.dirname(backup_path), exist_ok=True)

            # 5. 备份原文件（移动，而非复制，节省空间）
            try:
                shutil.move(filepath, backup_path)
            except Exception as e:
                errors.append(f"备份失败 {rel_path}: {e}")
                continue

            # 6. 压缩并保存到原位置（文件名不变）
            try:
                compress_to_webp(backup_path, filepath, QUALITY)
                processed += 1
                old_size = os.path.getsize(backup_path)
                new_size = os.path.getsize(filepath)
                print(f"✅ {rel_path}  {old_size//1024}KB → {new_size//1024}KB ({new_size/old_size*100:.1f}%)")
            except Exception as e:
                # 压缩失败，尝试恢复原文件
                shutil.move(backup_path, filepath)
                errors.append(f"压缩失败 {rel_path}: {e}")
                continue

    # 统计报告
    print("\n" + "="*60)
    print(f" 处理完成！")
    print(f"  总文件数：{total_files}")
    print(f"  跳过（≤300KB）：{skipped_small}")
    print(f"  跳过（已是WebP）：{skipped_webp}")
    print(f"  跳过（非图片）：{skipped_nonimage}")
    print(f"  成功压缩：{processed}")
    if errors:
        print(f"  错误数量：{len(errors)}")
        for err in errors:
            print(f"    ⚠️ {err}")
    print("="*60)

if __name__ == "__main__":
    main()