private void Stretch(object sender, EventArgs e)
{
    foreach (DataGridViewImageColumn column in
        dataGridView1.Columns)
    {
        column.ImageLayout = DataGridViewImageCellLayout.Stretch;
        column.Description = "Stretched";
    }
}

private void ZoomToImage(object sender, EventArgs e)
{

    foreach (DataGridViewImageColumn column in
        dataGridView1.Columns)
    {
        column.ImageLayout = DataGridViewImageCellLayout.Zoom;
        column.Description = "Zoomed";
    }
}

private void NormalImage(object sender, EventArgs e)
{

    foreach (DataGridViewImageColumn column in
        dataGridView1.Columns)
    {
        column.ImageLayout = DataGridViewImageCellLayout.Normal;
        column.Description = "Normal";
    }
}