加入图片缓存，每次从文件系统中提取相关的图片，加载成bytes，后续使用时直接从缓存中提取。减少IO读取次数，提高发送性能

plugins/xiuren_image/images_cache.py

@@ -2,7 +2,8 @@ import os
 import time
 import random
 import asyncio
-from typing import Optional, List
+from typing import Optional, List, Dict
+from collections import deque
 
 import logging
 
@@ -16,10 +17,15 @@ class ImageCacheManager:
     LAST_UPDATE_TIME_KEY = "group:images:last_update_time"
     BATCH_SIZE = 500
 
-    def __init__(self, image_folder: str):
+    def __init__(self, image_folder: str, cache_size: int = 5):
         self.image_folder = image_folder
         self.redis = DBConnectionManager.get_instance().get_redis_connection()
         self.image_extensions = {'.jpg', '.jpeg', '.png', '.gif', '.bmp', '.tiff', '.webp'}
+        
+        # 内存缓存相关
+        self.cache_size = cache_size
+        self.image_bytes_cache = deque(maxlen=cache_size)  # 使用deque作为LRU缓存
+        self.is_refilling = False  # 防止重复填充缓存
 
     def _get_last_update_time(self) -> float:
         ts = self.redis.get(self.LAST_UPDATE_TIME_KEY)
@@ -112,3 +118,86 @@ class ImageCacheManager:
         except Exception as e:
             logger.error(f"获取随机图片失败: {e}")
         return None
+
+    def _load_image_bytes(self, image_path: str) -> Optional[bytes]:
+        """从磁盘加载图片的bytes数据"""
+        try:
+            with open(image_path, 'rb') as f:
+                return f.read()
+        except Exception as e:
+            logger.error(f"读取图片文件失败 {image_path}: {e}")
+            return None
+
+    def _refill_cache(self):
+        """重新填充缓存"""
+        if self.is_refilling:
+            return
+        
+        self.is_refilling = True
+        try:
+            logger.info("开始重新填充图片缓存...")
+            
+            # 获取多个随机图片路径
+            redis_key = self.IMAGE_KEY_PREFIX + "all"
+            image_paths = []
+            
+            # 获取比缓存大小多一点的图片路径，以防有些文件读取失败
+            for _ in range(self.cache_size + 2):
+                try:
+                    img = self.redis.srandmember(redis_key)
+                    if img:
+                        path = img.decode('utf-8') if isinstance(img, bytes) else img
+                        # 检查路径是否已经在缓存中
+                        existing_paths = [item['path'] for item in self.image_bytes_cache]
+                        if path not in existing_paths:
+                            image_paths.append(path)
+                except Exception as e:
+                    logger.error(f"获取随机图片路径失败: {e}")
+                    continue
+            
+            # 加载图片bytes并添加到缓存
+            loaded_count = 0
+            for path in image_paths:
+                if loaded_count >= self.cache_size:
+                    break
+                    
+                image_bytes = self._load_image_bytes(path)
+                if image_bytes:
+                    self.image_bytes_cache.append({
+                        'path': path,
+                        'bytes': image_bytes
+                    })
+                    loaded_count += 1
+            
+            logger.info(f"缓存填充完成，新增 {loaded_count} 张图片")
+            
+        except Exception as e:
+            logger.error(f"填充缓存失败: {e}")
+        finally:
+            self.is_refilling = False
+
+    def get_cached_image_bytes(self) -> Optional[Dict[str, any]]:
+        """
+        从缓存中获取图片bytes数据
+        返回格式: {'path': str, 'bytes': bytes}
+        """
+        # 如果缓存为空，立即填充
+        if not self.image_bytes_cache:
+            self._refill_cache()
+            if not self.image_bytes_cache:
+                return None
+        
+        # 从缓存中取出一个图片
+        cached_image = self.image_bytes_cache.popleft()
+        
+        # 如果缓存中只剩最后一个，异步填充缓存
+        if len(self.image_bytes_cache) <= 1:
+            # 使用线程池异步填充，避免阻塞
+            import threading
+            threading.Thread(target=self._refill_cache, daemon=True).start()
+        
+        return cached_image
+
+    def get_cached_image_count(self) -> int:
+        """获取当前缓存中的图片数量"""
+        return len(self.image_bytes_cache)