submodule对gitea不管用，所以直接拉了一份拉格兰

Lagrange.Core/Lagrange.OneBot/Message/Entity/ImageSegment.cs

@@ -0,0 +1,46 @@
+using System.Text.Json.Serialization;
+using Lagrange.Core.Message;
+using Lagrange.Core.Message.Entity;
+
+namespace Lagrange.OneBot.Message.Entity;
+
+[Serializable]
+public partial class ImageSegment(string url, string filename, string summary = "[图片]", int subType = 0)
+{
+    public ImageSegment() : this("", "") { }
+
+    [JsonPropertyName("file")] [CQProperty] public string File { get; set; } = url;
+    
+    [JsonPropertyName("filename")] public string Filename { get; set; } = filename;
+    
+    [JsonPropertyName("url")] public string Url { get; set; }  = url;
+
+    [JsonPropertyName("summary")] public string Summary { get; set; } = summary;
+    
+    [JsonPropertyName("subType")] public int SubType { get; set; } = subType;
+}
+
+[SegmentSubscriber(typeof(ImageEntity), "image")]
+public partial class ImageSegment : SegmentBase
+{
+    public override void Build(MessageBuilder builder, SegmentBase segment)
+    {
+        if (segment is ImageSegment imageSegment and not { File: "" } && CommonResolver.ResolveStream(imageSegment.File) is { } stream)
+        {
+            builder.Add(new ImageEntity
+            {
+                FilePath = imageSegment.Filename,
+                ImageStream = new Lazy<Stream>(stream),
+                Summary = imageSegment.Summary,
+                SubType = imageSegment.SubType
+            });
+        }
+    }
+
+    public override SegmentBase FromEntity(MessageChain chain, IMessageEntity entity)
+    {
+        if (entity is not ImageEntity imageEntity) throw new ArgumentException("Invalid entity type.");
+
+        return new ImageSegment(imageEntity.ImageUrl, imageEntity.FilePath, imageEntity.ToPreviewText(), imageEntity.SubType);
+    }
+}