FEAT: support for #BackBmp

Author: QingQiz

BmsToOsu/Converter/Osu.cs

@@ -63,7 +63,11 @@ public static (string, HashSet<string> fileToCp) ToOsuBeatMap(
 
         var bg = "";
 
-        if (File.Exists(Path.Join(dir, data.Metadata.StageFile)))
+        if (File.Exists(Path.Join(dir, data.Metadata.BackBmp)))
+        {
+            bg = data.Metadata.BackBmp;
+        }
+        else if (File.Exists(Path.Join(dir, data.Metadata.StageFile)))
         {
             bg = data.Metadata.StageFile;
         }

BmsToOsu/Entity/BmsFileData.cs

@@ -193,6 +193,16 @@ private static BmsFileData CompileBmsToObj(string fp)
 
                 metadata.StageFile = stageFile;
             }
+            else if (line.WithCommand("#BACKBMP", out var backBmp))
+            {
+                if (backBmp.IsEmpty())
+                {
+                    Log.Warn($"{fp}: #BACKBMP is invalid, ignoring (Line: {i})");
+                    continue;
+                }
+
+                metadata.BackBmp = backBmp;
+            }
             else if (line.WithCommand("#banner", out var banner))
             {
                 if (banner.IsEmpty())

BmsToOsu/Entity/BmsMetadata.cs

@@ -8,6 +8,7 @@ public class BmsMetadata
     public string Difficulty = "";
     public string StageFile = "";
     public string Subtitle = "";
+    public string BackBmp = "";
     public List<string> SubArtists { get; } = new();
     public string Banner = "";
 }