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File Handling


									File Handling

Converting Files
         Converting Files

 Files can be converted from one format to
  another. Files can be “saved as” and the option
  dropdown will give you several options.
 Files can be exported and imported into various
  software packages.
 The size of a bitmap graphic file saved to disk
  depend upon the format of the file and the options
  taken when saving it.
 Vector files are usually a lot smaller and do not
  have save options for controlling file size
  because they are already as small as they will
 Controlling the file size is achieved by setting the
  compression or quality level when saving the
 The same graphic file might have different sizes
  using JPEG quality settings.
   Graphic sizes with different
   JPEG quality settings.

100%    90%     60%     40%    10%

440KB   216KB   116KB   92KB   41KB
    Graphic sizes in different

 BMP    GIF    JPG     PNG       TIF

2305KB 209KB   440KB   348KB 2305KB
 File format is the way the graphic is internally
  structured. Each file format uses a different
  structure – a program using that format must be
  able to understand the structure so it knows
  how to show the graphic on the screen, print it,
  edit it etc.

 Compression techniques are used to reduce the
  disk size of a file. Being able to make a file size
  smaller is very important if file size is an issue
  (web design)
 File size is important if the file is to be
  transmitted to another location (a small file
  arrives faster)
 File size is important is there is a small amount
  of storage space ( the file needs to be reduced in
  size to fit)
              Re-cap on Vector /Bitmap
 Vector graphics follow mathematical rules.
  Shapes are understood by vector graphics
  software as coordinate points joined by lines with
  a defined fill.

A line joining points may be
straight or curved and has
properties such as thickness,
colour, solid/dashed. There
could be no fill, making the
shape transparent or it could
have more than one colour or

 Bitmap or raster graphics are pixel orientated
  meaning that the image is made from a lot of pixels
  each a tiny dot in the image with a colour. In
  specific software you can zoom in enough to edit
  individual pixels.
 The mathematical way in which vector images are
  stored and manipulated makes them easy to edit
  and re-size and result in small file sizes.

 Bitmap images allow editing that is much more
  complex than that possible with vectors.

 Re-sizing a bitmap needs software to analyse the
  pixels in the image, then recreate a new set of
  pixels to make the image a new size.
 The will be loss of quality and there will always
  be a limit to how large a bitmap can be
  acceptably enlarged.

 As the colour information of every pixel needs to
  be stored in a bitmap image the file size can end
  up enormous.
               Vector              Bitmap
File Size      Small               Large files sizes,
                                   especially big
                                   pictures with large
                                   colour depth
Scaling        Very scalable to    Pixilation occurs
               any size without
               loss of quality
How created    User created with   Scanner or digital
               mouse of graphics   camera
Typical uses   Diagrams            Photographs

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