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Thread: Fractal text compression, imperfect match LZ and distortion-resistant hash function?

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  1. #1
    Join Date
    Nov 2013
    Kraków, Poland
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    Lightbulb Fractal text compression, imperfect match LZ and distortion-resistant hash function?

    There is a nice old concept for fractal compression of pictures: trying to find self-similarities and utilize them, for example encoding the mappings and differences:

    It didn’t seem to be successful, however maybe analogous approach could be reasonable for text or binary file compression?
    Specifically, while standard LZ schemes require perfect match for a sequence, there should be much more sequences with a nearly perfect match – it might be beneficial to extend LZ scheme to allow also for imperfect match and then encode the differences: for example byte sequence to XOR with, with dominating zeros – such difference could be cheaply stored using entropy coder.

    The problem is that finding similar sequences (by encoder) seems very costly.
    This is a very common task in DNA alignment and a few days ago I have realized that such search can be done in a relatively cheap way:
    Specifically, rate distortion theory allows to find Distortion-Resistant Hashing (DRH): hash values which are not changed while small distortion of object (like sequence).
    So searching for similar sequences can be reduced to having the same DRH value, and such collisions are relatively cheap to find.

    Does LZ scheme which (additionally!) allows partial match and then coding of differences seem reasonable? Have you met with such approaches?
    What other applications of distortion-resistant hashing can you think of?

  2. Thanks (2):

    Cyan (19th February 2016),Turtle (20th February 2016)

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