Why can't I scan the label I received from the printer with the barcode reader?

Question

I create a barcode with the value entered in the Winforms application and print it with the printer. Afterwards, when I want to scan it with a barcode reader, I cannot scan it. This is my code:

private void GenerateBarcodeButton_Click(object sender, EventArgs e)
{
    if (!String.IsNullOrEmpty(textBox1.Text))
    {
        pictureBox1.Image = Zen.Barcode.BarcodeDrawFactory.Code128WithChecksum.Draw(textBox1.Text, 50, 2);
    }
    else
    {
        MessageBox.Show("Please enter the barcode number you want to generate.");
    }
}
public void PrintPicture(object sender, PrintPageEventArgs e)
{
    Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
    // bmp.SetResolution(203, 203);
    pictureBox1.DrawToBitmap(bmp, new Rectangle(0, 0, pictureBox1.Width, pictureBox1.Height));
    e.Graphics.DrawImage(bmp, 20, 20, new System.Drawing.RectangleF(0, 0, bmp.Width, bmp.Height), System.Drawing.GraphicsUnit.Pixel);
}

private void Print_Click(object sender, EventArgs e)
{
    PrintDialog pd = new PrintDialog();
    PrintDocument pDoc = new PrintDocument();
    pDoc.PrintPage += PrintPicture;
    pd.Document = pDoc;
    if (pd.ShowDialog() == DialogResult.OK)
    {
        pDoc.Print();
    }
}

The printer model I use for printing is Godex G300. Where did I go wrong?

Answer 1

The problem was that I didn't set the DPI. I added this line to the code.

bmp.SetResolution(203, 203);

This is the new method:

        private void PrintPicture(object sender, PrintPageEventArgs e)
        {
            Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            bmp.SetResolution(203, 203);
            pictureBox1.DrawToBitmap(bmp, new Rectangle(0, 0, pictureBox1.Width, pictureBox1.Height));
            e.Graphics.DrawImage(bmp, 38, 10);
            bmp.Dispose();
        }