adam's notes

Printer Drivers and Page Description Languages

  • Applications that support printing are typically what you see is what you get (WYSIWYG)
    • the screen and print output are supposed to be identical
      • printer driver provides an interface between the print device and the operating system
      • each client must be installed with a suitable driver (64-bit OS ⇒ 64-bit driver)
  • appropriate print driver will be installed when the print device connects
    •  referred to as Plug and Play (PnP)
  • may need to add the driver manually or choose a driver version with support for a particular page description language (PDL)
    • used to create a raster file from the print commands sent by the software application
      • raster file is a dot-by-dot description of where the printer should place ink
    • PDL supports the following features:
      • Scalable fonts
        • originally, characters were printed as bitmaps
          • bitmap font consists of dot-by-dot images of each character at a particular font size
          • meant that the character could only be printed at sizes defined in the font
        • Scalable fonts are described by vectors
          • vector font consists of a description of how each character should be drawn
          • can be scaled up or down to different font sizes
        • All Windows printers support scalable TrueType or OpenType fonts.
      • Vector graphics
        • scalable images are built from vectors
        • describe how a line should be drawn rather than provide a pixel-by-pixel description
      • Color printing
        • computer displays use an additive red, green, blue (RGB) color model
        • print devices use a subtractive model that uses the reflective properties of cyan, magenta, yellow, and black (CMYK) inks
        • A PDL’s support for a particular color model provides an accurate translation between on-screen color and print output
          • ensures that different devices produce identical output
    • choice of PDL is largely driven by compatibility with software applications
      • Adobe PostScript is a device independent PDL
        • used for professional desktop publishing and graphical design output
      • HP’s Printer Control Language (PCL) is more closely tied to individual features of printer models
        • can introduce some variation in output depending on the print device
        • usually a bit faster than PostScript
      • Microsoft’s XML paper specification (XPS) PDL
        • default for Windows print devices

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