Printing bitmaps using CPCL

I've had no end of grief trying to print a PCX to a Zebra Printer using the CPCL printer language. Silly me, didn't notice the EG command (expanded graphics) so there was no need to convert my BMP to a PCX and then struggle with binary data.

I still had a bit of grief working out how to print using the EG command because the documentation is quite frankly crap. The expected command format is

EG {WidthInBytes} {HeightInPixels} {XPos} {YPos} {Data}\r\n


The printer expects a 1 bit pixel matrix. So if pixel(0, 0) is set you will set "80" in the data. If pixel(0, 0) is set and pixel (7, 0) is also set you would sent "81". Basically what you need to do is to read each set of 8 horizontal pixels and then use bit operations to create a byte value 0..255, and then output this as hex 00..FF.

Here's the routine :-)

  public void DrawBitmap(Bitmap bmp, int xPosition, int yPosition)
  {
   if (bmp == null)
    throw new ArgumentNullException("bmp");

   //Make sure the width is divisible by 8
   int loopWidth = 8 - (bmp.Width % 8);
   if (loopWidth == 8)
    loopWidth = bmp.Width;
   else
    loopWidth += bmp.Width;

   DataString.Append(string.Format("EG {0} {1} {2} {3} ", loopWidth / 8, bmp.Height, xPosition, yPosition));

   for (int y = 0; y < bmp.Height; y++)
   {
    int bit = 128;
    int currentValue = 0;
    for (int x = 0; x < loopWidth; x++)
    {
     int intensity;

     if (x < bmp.Width)
     {
      Color color = bmp.GetPixel(x, y);
      intensity = 255 - ((color.R + color.G + color.B) / 3);
     }
     else
      intensity = 0;

     if (intensity >= 128)
      currentValue |= bit;
     bit = bit >> 1;
     if (bit == 0)
     {
      DataString.Append(currentValue.ToString("X2"));
      bit = 128;
      currentValue = 0;
     }
    }//x
   }//y
   DataString.Append("\r\n");
  }