refactor(game-event): 优化赛事小程序码生成服务

- 移除PDF生成线程池配置
- 删除图片文件头常量定义
- 简化图片处理逻辑，移除白色背景填充
- 优化图像渲染性能

ruoyi-modules/ruoyi-game-event/src/main/java/org/dromara/system/service/impl/GameEventServiceImpl.java

@@ -89,17 +89,6 @@ public class GameEventServiceImpl implements IGameEventService {
     private FileUploadConfig fileUploadConfig;
     @Resource
     private ISysOssService sysOssService;
-    private static final ExecutorService PDF_GENERATION_EXECUTOR =
-        Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors() * 2);
-    // 常见图片类型的文件头（前几个字节）
-    private static final String[] IMAGE_HEADER_PREFIXES = {
-        "FFD8FF", // JPEG
-        "89504E47", // PNG
-        "47494638", // GIF
-        "49492A00", // TIFF (little endian)
-        "4D4D002A", // TIFF (big endian)
-        "424D"      // BMP
-    };
 
     /**
      * 更新赛事小程序码
@@ -1166,11 +1155,6 @@ public class GameEventServiceImpl implements IGameEventService {
             g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
             g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
 
-            // 填充背景色为白色（防止透明背景显示为黑色）
-            g2d.setColor(Color.WHITE);
-            g2d.fillRect(0, 0, targetWidth, targetHeight);
-            log.info("已填充白色背景");
-
             // 将原始模版图片拉伸/缩放到目标画布尺寸
             boolean drawResult = g2d.drawImage(originalTemplate, 0, 0, targetWidth, targetHeight, null);
             if (!drawResult) {