Chagall Reference   Picture resolution     12.5.93
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   Monochrome pictures are made up of only black 
   and white pixels (colour depth: 1-bit), 
   halftone pictures of up to 256 grey tones 
   (colour depth: 8-bit) and colour pictures 
   finally of up to 16.7 million colours
   (colour depth: 24-bit). Since the colour depth
   determines the memory requirements, you should 
   not choose a higher colour depth than necessary 
   to suit the current task.

   The picture width and height can be calculated 
   by the following formula:

      Picture width  = Resolution x width in pixels
      Picture height = Resolution x height in pixels

   You should note that the resolution is always
   given in dpi (dots per inch), where a dot is 
   equivalent to a pixel.

