private void btnCreate_Click(object sender, EventArgs e)
        {     // create tiles
            if (tbLoadImage.Text == "")
            { // image file not selected
                MessageBox.Show("No tiles sheet is loaded", "Create Tiles", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                return;
            }

            DialogResult saveTiles = this.saveTilesDialog.ShowDialog();

            if (saveTiles == DialogResult.OK)
            {   // save tiles
                string        folderName = this.saveTilesDialog.SelectedPath + "\\" + tbName.Text;
                DirectoryInfo di         = Directory.CreateDirectory(folderName);

                Cursor.Current = Cursors.WaitCursor;
                CreateTiles(folderName);
                Cursor.Current = Cursors.Default;

                if (MessageBox.Show("Load to Tile Library now?", "Finished", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
                {   // load tiles?
                    _parent_form.AddTiles(folderName);
                }

                this.Close();
            }
        }