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From: den@hpfinote.HP.COM (Don Novy)
Newsgroups: comp.graphics
Subject: Re: Compressing GIF images
Message-ID: <15040011@hpfinote.HP.COM>
Date: 6 Jul 90 21:51:54 GMT
References: <127225@csb8.encore.com>
Organization: Hewlett Packard CICD
Lines: 17


  GIF files are already compressed! The header containing the image size and
color map data is not compressed, but this is a small part of the total GIF
file. The raster data uses a modified LZW compression scheme.

  You can see how efficient this is by multiplying the number of pixels by the
number of bits per pixel and dividing by 8 to convert to bytes. GIF files are
really not THAT big compared to storing the raw data.

  You may see a small difference in the compression ratio by changing the order
of the pixels to be compressed; i.e. changing from sequential order to
interleaved order, or vice-versa.


Don Novy
Hewlett-Packard
den@hpfitst2.hp.com