优化Bitmap获取过程

SpineViewer/Controls/SpineListView.cs

@@ -500,10 +500,8 @@ namespace SpineViewer.Controls
                 foreach (int i in listView.SelectedIndices)
                 {
                     var spine = spines[i];
-                    var image = spine.Preview;
                     var path = Path.Combine(Program.TempDir, $"{spine.ID}.png");
-                    using (var clone = new Bitmap(image))
-                        clone.Save(path);
+                    spine.Preview.Save(path);
                     fileDropList.Add(path);
                 }
             }

SpineViewer/Exporter/ExportHelper.cs

@@ -72,7 +72,7 @@ namespace SpineViewer.Exporter
         {
             image.SaveToMemory(out var imgBuffer, "bmp");
             using var stream = new MemoryStream(imgBuffer);
-            return new(new Bitmap(stream));
+            return new(new Bitmap(stream)); // 必须重复构造一个副本才能摆脱对流的依赖, 否则之后使用会报错
         }
     }
 

SpineViewer/Spine/Spine.cs

@@ -380,7 +380,7 @@ namespace SpineViewer.Spine
                     using var img = tex.Texture.CopyToImage();
                     img.SaveToMemory(out var imgBuffer, "bmp");
                     using var stream = new MemoryStream(imgBuffer);
-                    preview = new Bitmap(stream);
+                    preview = new Bitmap(new Bitmap(stream)); // 必须重复构造一个副本才能摆脱对流的依赖, 否则之后使用会报错
                 }
                 return preview;
             }