Python 批量压缩图片体积：在清晰度和大小之间找平衡

用 Python Pillow 批量压缩图片，通过调整 quality 参数、optimize、转 WebP 把大图压小，支持遍历目录、对比压缩前后体积，附完整代码和注意事项。

场景痛点

单反拍的原图一张 5-10MB，手机相册导出的图也动不动 3-5MB，传到网站、邮件附件、微信群里都太慢。用 Photoshop 一张张导出，几十张图要点到手酸，还记不住每张压到多少合适。用 Python 批量跑一遍，统一把体积压到目标范围，肉眼几乎看不出差别，文件能小 60%-80%。

用到的库

pip install Pillow

完整代码

import os
from PIL import Image

SRC_EXTS = (".jpg", ".jpeg", ".png", ".webp")


def human_size(n):
"""把字节数转成可读字符串"""
for unit in ("B", "KB", "MB"):
if n < 1024:
return f"{n:.1f}{unit}"
n /= 1024
return f"{n:.1f}GB"


def compress_one(src_path, dst_path, quality=80):
"""压缩单张图片，quality 1-95，越大越清晰"""
img = Image.open(src_path)
# PNG 带透明通道，压 JPEG 会丢透明，统一处理
if img.mode not in ("RGB", "L"):
img = img.convert("RGB")
img.save(dst_path, "JPEG", quality=quality, optimize=True, progressive=True)
old = os.path.getsize(src_path)
new = os.path.getsize(dst_path)
ratio = (1 - new / old) * 100 if old else 0
print(f"{os.path.basename(src_path)}: {human_size(old)} -> {human_size(new)}，减小 {ratio:.1f}%")


def batch_compress(src_dir, dst_dir, quality=80):
"""批量压缩目录下所有图片，输出为 JPEG"""
os.makedirs(dst_dir, exist_ok=True)
for root, _, files in os.walk(src_dir):
for name in files:
if not name.lower().endswith(SRC_EXTS):
continue
src_path = os.path.join(root, name)
rel = os.path.relpath(src_path, src_dir)
new_name = os.path.splitext(rel)[0] + ".jpg"
dst_path = os.path.join(dst_dir, new_name)
os.makedirs(os.path.dirname(dst_path), exist_ok=True)
try:
compress_one(src_path, dst_path, quality)
except Exception as e:
print(f"失败：{src_path}，原因：{e}")


def main():
src_dir = "./photos"
dst_dir = "./photos_compressed"
batch_compress(src_dir, dst_dir, quality=80)


if __name__ == "__main__":
main()