Changing raster image paths in drawing to relative paths

By Balaji Ramamoorthy

Here is a code snippet to change the raster image paths in a drawing from absolute path to one that is relative to the host drawing path. Raster images that already have a relative path set remain unchanged.

 using  System.IO;

 Document doc 

 = Application.DocumentManager.MdiActiveDocument;

 Editor ed = doc.Editor;

 string  dwgFilePath = null ;

 dwgFilePath = @"D:\Temp\Test.dwg" ;

 using  (Database db = new  Database(false , true ))

 {

     db.ReadDwgFile(dwgFilePath, 

         FileOpenMode.OpenForReadAndWriteNoShare, 

         false , "" );

     using  (Transaction tr 

         = db.TransactionManager.StartTransaction())

     {

         DBDictionary nod = tr.GetObject(

             db.NamedObjectsDictionaryId, 

             OpenMode.ForRead) as  DBDictionary;

         ObjectId imageDictId = nod.GetAt("ACAD_IMAGE_DICT" );

         DBDictionary imageDict 

             = tr.GetObject(imageDictId, OpenMode.ForRead) 

                 as  DBDictionary;

         foreach  (DBDictionaryEntry dbDictEntry in  imageDict)

         {

             RasterImageDef rasterImageDef = tr.GetObject(

                 dbDictEntry.Value, 

                 OpenMode.ForWrite) as  RasterImageDef;

             ed.WriteMessage("{0} Old SourcefileName : {1}" , 

             Environment.NewLine, rasterImageDef.SourceFileName);

             try 

             {

                 if  (File.Exists(rasterImageDef.SourceFileName))

                 {

                     dynamic dwgPathUri 

                             = new  Uri(dwgFilePath);

                     dynamic rasterImagePathUri 

                         = new  Uri(rasterImageDef.SourceFileName);

                     // Make the raster image path  

                     // relative to the drawing path 

                     dynamic relativeRasterPathUri 

                         = dwgPathUri.MakeRelativeUri

                                 (rasterImagePathUri);

                     // Set the source path as relative 

                     rasterImageDef.SourceFileName 

                     = Uri.UnescapeDataString(

                         relativeRasterPathUri.ToString());

                     ed.WriteMessage(

                         "{0} Image path changed to : {1}" , 

                         Environment.NewLine, 

                         rasterImageDef.SourceFileName);

                     // Reload for AutoCAD to  

                     // resolve active path 

                     rasterImageDef.Load();

                     // Check if we found it 

                     ed.WriteMessage("{0} Image found at : {1}" ,

                     Environment.NewLine, 

                     rasterImageDef.ActiveFileName);

                 }

             }

             catch  (UriFormatException ex)

             {

                 // Will ignore this. 

                 // If the raster image path is already relative 

                 // we might catch this exception 

             }

         }

         tr.Commit();

     }

     db.SaveAs(db.OriginalFileName, 

             true , 

             db.OriginalFileVersion, 

             db.SecurityParameters);

 }