How to print a converted text to image with thermal printer using ESC/POS in C#

Question

I need to print a currency symbol with a thermal printer using ECS/POS. The currency symbol is not available in any of the printer's character tables. So, what I did was to convert the currency symbol and the amount text to an image which is displayed in a picturebox. However, sending this picturebox image (bitmap) to the printer, a 1e1e1e1e (solid) image was printed, converting the image to gray-scale did not make any difference. Below is code to convert text to image:

public static Bitmap Convert_ValueToImage(string ValueText, string Fontname, int Fontsize)
{
    //creating bitmap image
    Bitmap ValueBitmap = new Bitmap(1, 1);
    //FromImage method creates a new Graphics from the specified Image.
    Graphics Graphics = Graphics.FromImage(ValueBitmap);

    // Create the Font object for the image text drawing.
    Font Font = new Font(Fontname, Fontsize);

    // Instantiating object of Bitmap image again with the correct size for the text and font.
    SizeF stringSize = Graphics.MeasureString(ValueText, Font);
    ValueBitmap = new Bitmap(ValueBitmap, (int)stringSize.Width, (int)stringSize.Height);
    Graphics = Graphics.FromImage(ValueBitmap);

    //Draw Specified text with specified format
    Graphics.DrawString(ValueText, Font, Brushes.Black, 0, 0);

    Font.Dispose();
    Graphics.Flush();
    Graphics.Dispose();

    return ValueBitmap; //return Bitmap Image
}

Usage:

private void btnConvertTextToImage_Click(object sender, EventArgs e)
{
    // Passing appropriate values to Convert Value to Image method
    this.pictureBoxValueImage.Image = Convert_ValueToImage((CurrencySymbol + " 5,500:00"), "Verdana", 20);
    this.pictureBoxValueImage.SizeMode = PictureBoxSizeMode.Normal;

    // Convert Value Image to Bitmap
    ValueImage = new Bitmap(this.pictureBoxValueImage.Image);       
}

What am I doing wrong?

Code to send bitmap to printer:

private void Print_Bipmap()
{
    int x;
    int y;
    int i;
    int RowBytes;
    byte n;
    Color Pixels;
    byte[,] ImageArray = new byte[bitmap.Width, bitmap.Height];

    // Calculate output size
    RowBytes = (bitmap.Width + 7) / 8;
    // Generate body of array
    for (y = 0; y < bitmap.Height; y++)
    { // Each row...
        for (x = 0; x < (bitmap.Width / 8); x++)
        { // Each 8-pixel block within row...
            ImageArray[x, y] = 0;
            for (n = 0; n < 8; n++)
            { // Each pixel within block...
                Pixels = bitmap.GetPixel(x * 8 + n, y);
                if (Pixels.GetBrightness() < 0.5)
                {
                    ImageArray[x, y] += (byte)(1 << (7 - n));
                }
            }
        }
    }

    comport_writeByte(18); //DC2
    comport_writeByte(42); //*
    comport_writeByte((byte)bitmap.Height); //r
    comport_writeByte((byte)RowBytes); //n

    for (y = 0; y < bitmap.Height; y++)
    {
        for (x = 0; x < RowBytes; x++)
        {
            comport_writeByte(ImageArray[x, y]); //[d1 ..... dn]
        }
    }
}