.rar files (How did they do it?)

Discussion in 'OS X and OS X Apps' started by wildcard, Jul 3, 2008.

  1. wildcard

    wildcard Active Member

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    check out the standalone dvd image

    http://ps2-scene.org/sms/eng/cdimage.htm

    I've encountered a number of this kind of rar'd file in my wanderings on the internet, and I can't figure out how they did it.

    the rar'd file is only 1.4MB but when unrar'd it becomes a 2GB iso image.

    I would really like to know how to do this so that I won't have too much trouble transferring files from the office to my home.

    Thanks in advance
     
  2. IronMan

    IronMan Member

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    Re: How did they do it?

    Well RAR is a compression format just like ZIP. However that 2GB ISO image is probably full of zeroes or any repetitive patterns that's why it was reduced to a mere 1.4MB. It depends on the file to be compressed. Text files compress a lot but binary files tend to have lower compression ratios. Try compressing a JPG file. It won't compress much.

    This is a general idea. That link displayed a webpage with bad layout [probably due to the filtering here in my ofc]. I don't have any idea what those image files are. But i suppose my explanation fits your question.
     
  3. lamski

    lamski PhilMUG Addict Member
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    Re: How did they do it?

    It would depend on the type of data you're trying to compress. Text files can have very high compression ratios. For binary data, it depends. Vector files tend to compress better that raw images, most movie files are already compressed so they can't be compressed any further.
     

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