Source : Free On-Line Dictionary of Computing

rasterising
     
         A transformation that can be applied to an image
        to prepare it for printing.  Rasterising reduces resolution by
        a factor of typically four to eight.  It also reduces
        sensitivity to paper properties.  Rasterising can be combined
        with {dithering}.
     
        [How does it work?]
     
        (2003-07-20)