3t

Steganograpy Software
  • Lossless compression is preferred when there is a requirement that the original information remain intact (as with steganographic images). The original message can be reconstructed exactly. This type of compression is typical in GIF2 and BMP3 images.
  • Lossy compression, while also saving space, may not maintain the integrity of the original image. This method is typical in JPG4 images and yields very good compression. 

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    2     Graphic Interchange Format developed by Compuserve to be a
          device-independent method of storing images.
    3     Windows and OS/2 bitmap picture file.
    4     Joint Photography experts Group (JPG/JPEG) is a device-
          independent method for storing images which supports 24-bit
          images.
  • (go back)

     

    • 74

    Background

    To illustrate the advantage of lossy compression, Renoir's Le Moulin de la Galette was retrieved as a 175,808 byte JPG image 1073 x 790 pixels with 16 million possible colors. The colors were maintained when converting it to a 24-bit BMP file but the file size became 2,649,019 bytes! Converting again to a GIF file, the colors were reduced to 256 colors (8-bit) and the new file is 775,252 bytes. The 256 color image is a very good approximation of Renoir's painting.

     


    Next Section: 3.2 Evaluation Method


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