阿里云 Serverless 图片处理实验（缩略图 + 水印）

# -*- coding: utf-8 -*-
import oss2
from PIL import Image, ImageDraw, ImageFont
import io
import os
import json
import traceback

# ===================== OSS 配置 =====================
OSS_ENDPOINT = os.environ.get('OSS_ENDPOINT')
OSS_BUCKET_NAME = os.environ.get('OSS_BUCKET_NAME', 'image-bucket')
ORIGINAL_FOLDER = 'original/'
PROCESSED_FOLDER = 'processed/'

# 注意：如果配置了函数计算的 RAM 角色，AK/SK 可以不从环境变量取，直接在 handler 中用 context 拿临时密钥更安全。
OSS_ACCESS_KEY_ID = os.environ.get('OSS_ACCESS_KEY_ID')
OSS_ACCESS_KEY_SECRET = os.environ.get('OSS_ACCESS_KEY_SECRET')

def handler(event, context):
    # 1. 【修复】将 bytes 类型的 event 解析为 dict
    try:
        evt_dict = json.loads(event)
    except Exception:
        print("无法解析 Event 为 JSON")
        return {"statusCode": 400, "body": "Invalid Event Format"}

    if 'events' not in evt_dict:
        print("非 OSS 触发事件")
        return {"statusCode": 400, "body": "非 OSS 触发事件"}

    # 初始化 OSS 客户端（优先尝试使用环境变量的长期密钥，若无则尝试取 context 中的临时 STS 密钥）
    creds = context.credentials
    ak = OSS_ACCESS_KEY_ID or creds.access_key_id
    sk = OSS_ACCESS_KEY_SECRET or creds.access_key_secret
    token = creds.security_token if not OSS_ACCESS_KEY_ID else None

    if token:
        auth = oss2.StsAuth(ak, sk, token)
    else:
        auth = oss2.Auth(ak, sk)
        
    bucket = oss2.Bucket(auth, OSS_ENDPOINT, OSS_BUCKET_NAME)

    for record in evt_dict['events']:
        key = record['oss']['object']['key']
        print(f"触发处理的 Key: {key}")

        # ====== 只处理 original/ 文件夹 ======
        if not key.startswith(ORIGINAL_FOLDER):
            print(f"跳过非 original/ 目录的文件: {key}")
            continue

        try:
            # 下载 OSS 对象
            obj = bucket.get_object(key)
            image_data = obj.read()

            # ====== 尝试打开图片，非图片跳过 ======
            try:
                img = Image.open(io.BytesIO(image_data))
            except Exception:
                print(f"非图片文件，跳过: {key}")
                continue

            print(f"原图大小: {img.size}, 模式: {img.mode}")

            # 2. 【修复】兼容 Pillow 10+ 的缩略图抗锯齿参数
            resample_algo = getattr(Image, 'Resampling', Image).LANCZOS
            img.thumbnail((200, 200), resample_algo)

            # ====== 透明 PNG 转换处理 ======
            if img.mode in ('RGBA', 'LA') or (img.mode == 'P' and 'transparency' in img.info):
                background = Image.new("RGB", img.size, (255, 255, 255))
                background.paste(img, mask=img.split()[-1])
                img = background
            elif img.mode != 'RGB':
                img = img.convert('RGB')

            # ====== 添加水印 ======
            draw = ImageDraw.Draw(img)
            text = "Serverless"
            try:
                font = ImageFont.truetype("/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf", 20)
            except Exception:
                font = ImageFont.load_default()
            
            # 3. 【修复】使用 textbbox 替代已废弃的 textsize
            if hasattr(draw, 'textbbox'):
                # textbbox 返回元组 (left, top, right, bottom)
                bbox = draw.textbbox((0, 0), text, font=font)
                text_width = bbox[2] - bbox[0]
                text_height = bbox[3] - bbox[1]
            else:
                # 兼容极老版本的 Pillow
                text_width, text_height = draw.textsize(text, font=font)

            draw.text((img.width - text_width - 10, img.height - text_height - 10),
                      text, fill=(255, 0, 0), font=font)

            # ====== 保存到内存并写回 OSS ======
            out_buffer = io.BytesIO()
            img.save(out_buffer, format='JPEG')
            out_buffer.seek(0)

            # 4. 【优化】保留相对路径结构，避免拍扁目录
            # 例如: original/sub/a.jpg -> processed/thumb_sub_a.jpg 或者 processed/sub/thumb_a.jpg
            # 这里采用截取掉 original/ 前缀，并在文件名前加 thumb_ 的方式
            relative_path = key[len(ORIGINAL_FOLDER):] 
            path_parts = relative_path.split('/')
            path_parts[-1] = f"thumb_{path_parts[-1]}"
            processed_key = f"{PROCESSED_FOLDER}{'/'.join(path_parts)}"

            bucket.put_object(processed_key, out_buffer)
            print(f"生成文件成功: {processed_key}")

        except Exception as e:
            print(f"处理 {key} 失败: {e}")
            traceback.print_exc()
            continue

    return {"statusCode": 200, "body": "处理完成"}