feat: 上传大图自动缩放，减小图片体积和带宽消耗

Co-authored-by: aider (deepseek/deepseek-v4-pro) <aider@aider.chat>

app.py

@@ -51,6 +51,38 @@ if not config.INDEX_FILE.exists():
         json.dump([], f, ensure_ascii=False, indent=2)
 
 
+# ---------- 图片缩放辅助函数 ----------
+def resize_image_if_large(filepath: str, max_width: int = 1200):
+    """如果图片宽度超过 max_width，则等比缩放并覆盖原文件。
+    不处理 GIF 文件（保留动画），若 Pillow 未安装则静默跳过。"""
+    try:
+        from PIL import Image
+    except ImportError:
+        return   # 不做任何处理，避免依赖问题
+
+    try:
+        img = Image.open(filepath)
+        w, h = img.size
+        if w <= max_width:
+            return
+        # 跳过 GIF（避免丢失动画）
+        if img.format == "GIF":
+            return
+        new_h = int(h * max_width / w)
+        img = img.resize((max_width, new_h), Image.LANCZOS)
+        # 保存时尽量保留原格式和质量
+        save_kwargs = {}
+        if img.format == "JPEG":
+            save_kwargs["quality"] = 85
+            save_kwargs["optimize"] = True
+        elif img.format == "PNG":
+            save_kwargs["optimize"] = True
+        img.save(filepath, format=img.format, **save_kwargs)
+    except Exception:
+        # 任何异常都静默跳过，不影响上传流程
+        pass
+
+
 @app.context_processor
 def inject_user_status():
     """向所有模板注入登录状态"""
@@ -180,6 +212,9 @@ def editor_upload_image():
     file_path = editor_uploads_dir / new_name
     file.save(str(file_path))
 
+    # ---------- 对上传的图片进行缩放 ----------
+    resize_image_if_large(str(file_path))
+
     # 生成可访问 URL 和 Markdown 片段
     image_url = f"/static/uploads/posts/editor_uploads/{new_name}"
     markdown_code = f"![{safe_name}]({image_url})"
@@ -281,7 +316,10 @@ def upload():
         if img and img.filename:
             filename = secure_filename(img.filename)
             if filename:
-                img.save(str(upload_dir / filename))
+                file_path = upload_dir / filename
+                img.save(str(file_path))
+                # ---------- 对上传的图片进行缩放 ----------
+                resize_image_if_large(str(file_path))
 
     # 读取 Markdown 内容
     with open(md_path, "r", encoding="utf-8") as f: