Error: when Image data convert to pdf from DataGridView tbl.

Question

Im trying to convert DataGridView data with image column which is filtered from my SQL Db into a PDF file in C# I wrote this code using iTextSharp!
but I got  Error like this: "unable to cast object of type System.Drawing.bitmap to type system byte[]"

Can anyone help me out kindly?

Here is My Code:
Thanks !!!

 

foreach (DataGridViewCell cell in row.Cells)
{
    if(row.Cells[0].Value!= null)
    {
        pdfTable.AddCell(row.Cells[0].Value.ToString());
    }

    if (row.Cells[1].Value != null)
    {
        byte[] img = (byte[])row.Cells[1].Value;
        pdfTable.AddCell(iTextSharp.text.Image.GetInstance(img));
   }
}