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Lempel Ziv compression implementation

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  Lempel Ziv compression implementation mathieu <mathieu.malaterre@gmail.com> - 2015-07-25 06:30 -0700
    Re: Lempel Ziv compression implementation Robert Wessel <robertwessel2@yahoo.com> - 2015-07-25 15:28 -0500
      Re: Lempel Ziv compression implementation mathieu <mathieu.malaterre@gmail.com> - 2015-07-28 03:55 -0700
        Re: Lempel Ziv compression implementation glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-28 17:41 +0000
        Re: Lempel Ziv compression implementation Dave Brown <0ntariokingston@gmail.com> - 2015-08-04 14:11 -0700

#3114 — Lempel Ziv compression implementation

Hi there,

I am starring at page 43 and up (5.4 Example For Lempel-Ziv encoding) from the following document:

ftp://medical.nema.org/medical/dicom/1989/PS2_1989.pdf

Does anyone recognize the associated algorithm ? Is it available in a publicly available library ?

Thanks much for comments

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#3115

On Sat, 25 Jul 2015 06:30:55 -0700 (PDT), mathieu
<mathieu.malaterre@gmail.com> wrote:

>Hi there,
>
>I am starring at page 43 and up (5.4 Example For Lempel-Ziv encoding) from the following document:
>
>ftp://medical.nema.org/medical/dicom/1989/PS2_1989.pdf
>
>Does anyone recognize the associated algorithm ? Is it available in a publicly available library ?
>
>Thanks much for comments


Page 11 seems to be clear that it's just LZW as described in the
original Welch paper, per reference #21.

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#3116

On Saturday, July 25, 2015 at 10:28:20 PM UTC+2, robert...@yahoo.com wrote:
> On Sat, 25 Jul 2015 06:30:55 -0700 (PDT), mathieu
> <mathieu.malaterre gmail.com> wrote:
> 
> >Hi there,
> >
> >I am starring at page 43 and up (5.4 Example For Lempel-Ziv encoding) from the following document:
> >
> >ftp://medical.nema.org/medical/dicom/1989/PS2_1989.pdf
> >
> >Does anyone recognize the associated algorithm ? Is it available in a publicly available library ?
> >
> >Thanks much for comments
> 
> 
> Page 11 seems to be clear that it's just LZW as described in the
> original Welch paper, per reference #21.

Any implementation out there that support 16bits input. Most implementations I found assume 8bits input.

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#3117

mathieu <mathieu.malaterre@gmail.com> wrote:
> On Saturday, July 25, 2015 at 10:28:20 PM UTC+2, robert...@yahoo.com wrote:
(snip) 
>> Page 11 seems to be clear that it's just LZW as described in the
>> original Welch paper, per reference #21.
 
> Any implementation out there that support 16bits input. 
> Most implementations I found assume 8bits input.

LZW finds repetitions in the data.  Repetitions in 16 bit data are
also repeitions in 8 bit data, so it will still find them.

LZW initializes the dictionary with all 8 bit values, which isn't
so bad.  If you made one that initialized with all 16 bit values,
it would have to start with 17 bit codes, which could be a lot
less efficient.

LZW also works well for smaller data, for example files full of
binary (ASCII '0' and '1') data, even if the actual 0's and 1's
are random, will compress well. It will find strings of 1's and
0's and code for them.

-- glen

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#3130

On Tuesday, July 28, 2015 at 6:55:48 AM UTC-4, mathieu wrote:
> On Saturday, July 25, 2015 at 10:28:20 PM UTC+2, robert...@yahoo.com wrote:
> > On Sat, 25 Jul 2015 06:30:55 -0700 (PDT), mathieu
> > <mathieu.malaterre gmail.com> wrote:
> > 
> > >Hi there,
> > >
> > >I am starring at page 43 and up (5.4 Example For Lempel-Ziv encoding) from the following document:
> > >
> > >ftp://medical.nema.org/medical/dicom/1989/PS2_1989.pdf
> > >
> > >Does anyone recognize the associated algorithm ? Is it available in a publicly available library ?
> > >
> > >Thanks much for comments
> > 
> > 
> > Page 11 seems to be clear that it's just LZW as described in the
> > original Welch paper, per reference #21.
> 
> Any implementation out there that support 16bits input. Most implementations I found assume 8bits input.

https://github.com/JavaScript-Packer/lzw-javascript-packer.js

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