Thumbnail is not generating after saving drawing file.

[RamanSBV]

Hi,

I am facing an issue while generating the thumbnail of the drawing file.

Thumbnail is generating fine for drawing file.

Once drawing file is saved using below statement,

Database.SaveAs(filePath,DwgVersion.Current);

Thumbnail generation method is returning null as given below.

byte bytCnt = br.ReadByte();

if (bytCnt <= 1)    //Means bytCnt value is 1;

return null;

Please help me on this issue

Regards,

Raman

[Alexander.Rivilis]

From Docs:

If the database executing the SaveAs() function is not the current database in the AutoCAD editor, then the thumbnail preview image is not saved to fileName. 

 To preserve previous thumbnail:

db.RetainOriginalThumbnailBitmap = true;
db.SaveAs (...);

[RamanSBV]

Hi,

Thanks for giving your comments on this.

As you mentioned, I have coded as below

Database db = newDatabase(false, true);

db.RetainOriginalThumbnailBitmap =true;

db.ReadDwgFile(filePath, FileOpenMode.OpenForReadAndAllShare, true, "");

db.SaveAs(filePath,DwgVersion.Current);

db.Dispose();

But still same issue.... 😞

Regards,

Raman

[Alexander.Rivilis]

Tested with AutoCAD 2013:

static int Ver = AcAp.Application.Version.Major;
// AutoCAD 2007...2012
[DllImport("acblock.arx", CallingConvention = CallingConvention.Cdecl, EntryPoint = "acdbMakeDrawingPreview")]
extern static private Int32 acdbMakeDrawingPreview12(IntPtr db, [MarshalAs(UnmanagedType.U1)] bool bUnused);
// AutoCAD 2013...
[DllImport("acblock.crx", CallingConvention = CallingConvention.Cdecl, EntryPoint = "acdbMakeDrawingPreview")]
extern static private Int32 acdbMakeDrawingPreview13(IntPtr db, [MarshalAs(UnmanagedType.U1)] bool bUnused);
static public Int32 acdbMakeDrawingPreview(Database db, bool bUnused)
{
  return (Ver == 18) ? acdbMakeDrawingPreview12(db.UnmanagedObject, bUnused) : acdbMakeDrawingPreview13(db.UnmanagedObject, bUnused);
}

[CommandMethod("BoxView", CommandFlags.Modal)]
public static void CrossView()
{
  Autodesk.AutoCAD.Windows.OpenFileDialog dlg = new Autodesk.AutoCAD.Windows
      .OpenFileDialog("Select dwg-file:", "", "dwg", "",
      Autodesk.AutoCAD.Windows.OpenFileDialog.OpenFileDialogFlags.AllowMultiple);
  DialogResult ds = dlg.ShowDialog();
  if (ds != DialogResult.OK) return;
  foreach (string path in dlg.GetFilenames()) {
    using (Database db = new Database(false, false)) {
      try {
        db.ReadDwgFile(path, FileOpenMode.OpenForReadAndReadShare, false, "");
        Point3d p1 = db.Extmin, p2 = db.Extmax;
        Point3d[] pts = new Point3d[4];
        pts[0] = new Point3d(p1.X, p1.Y, 0);  pts[1] = new Point3d(p1.X, p2.Y, 0);
        pts[2] = new Point3d(p2.X, p2.Y, 0);  pts[3] = new Point3d(p2.X, p1.Y, 0);

        using (BlockTableRecord btr = db.CurrentSpaceId.Open(OpenMode.ForWrite) as BlockTableRecord) {
          using (Polyline3d pl = new Polyline3d(Poly3dType.SimplePoly, new Point3dCollection(pts), true)) {
            btr.AppendEntity(pl);
          }
        }
        db.CloseInput(true);
        // acdbMakeDrawingPreview(db,true); // Making new preview
        db.RetainOriginalThumbnailBitmap = true;
        System.Drawing.Bitmap bm = db.ThumbnailBitmap;
        db.SaveAs(path, DwgVersion.Current);
      }
      catch (Autodesk.AutoCAD.Runtime.Exception ex) {
        Editor ed = Autodesk.AutoCAD.ApplicationServices.Application
                     .DocumentManager.MdiActiveDocument.Editor;
        ed.WriteMessage(ex.ToString());
      }
    }
  }
}

Preview has only previous Thumbnail, i.e. polyline is not visible in preview.
I've tried to using very old undocumented function acdbMakeDrawingPreview to make new preview but without success.

[FredTomke]

Hi, works for me very well in combination with db.Wblock.

I'm creating new database, zoom to extents within a transaction, and write the tumbnail as seen above after the zoom-transaction.

True uses view of current database, False uses the newly created view in the side database.

    public static bool Wblock(string strFile, Point3d ptPoint, ObjectIdCollection lstObj)
    {
      bool isSuc = false;
      if (lstObj.Count > 0)
      {
        Database oDbSource = lstObj[0].Database;

        try
        {
          using (Database oNewDb = new Database(true, false))
          {
            oDbSource.Wblock(oNewDb, lstObj, ptPoint, DuplicateRecordCloning.Ignore);

            TransactionHelper.RunIn(oNewDb, delegate(Transaction oTrans)
            {
              oNewDb.ZoomExtents(1.05);
            });
            // nothing else then acdbMakeDrawingPreview13
            CreateDrawingPreview(oNewDb, false); 
            oNewDb.SaveAs(strFile, DwgVersion.Newest);
          }
          isSuc = true;
        }
        catch { }
      }
      return isSuc;
    }

 Thanks for the sample.

Regards, Fred