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From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: Frank Peters <frank.peters@comcast.net>
Subject: Re: [Tiff] LZW Compression with 16-bit TIFF
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Status:   

On Fri, 3 Mar 2006, Frank Peters wrote:
>>
>> 16 bit data can be difficult to compress.  Have you tried enabling
>> horizontal differencing?
>>
>>    TIFFSetField(tiff,TIFFTAG_PREDICTOR,2);
>
> Why should 16-bit data be any different in principle that 8-bit
> data?  A change in data length should not have any bearing on
> compression (at least that's what I would first think).

The more levels available, the more difficult the data is to compress. 
That is due to less opportunity for repeated codes.

> As for horizontal differencing, supposedly that's what the "-c lzw:2"
> option accomplishes.  Is there another way to enable this by setting
> some parameter in the source code and then recompiling?

The line of code that I posted? :-)

Bob
======================================
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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