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To: "Jan Edmundson" <janedm@rsv.se>
Cc: <tiff@olympiakos.com>
Subject: Re: Decode group4
References: <008f01c254c2$941ccfe0$7f08090a@A25463>
From: fdc@cliwe.ping.de (Frank D. Cringle)
Date: 05 Sep 2002 12:21:47 +0200
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"Jan Edmundson" <janedm@rsv.se> writes:
> Hi all, I am currently in the process of creating a class
> implementation of the fax group 4 codec.

In which language? C++?

> I have a class namned CCodec
> with 2 methods Decode and Encode. I am focusing on the decoding bit at
> the moment. I have a hypothesis that the Decode method would be
> sufficently declared as follows: Decode( BYTE* pDest, DWORD
> dwDestSize, BYTE* pSrc, DWORD dwSrcSize, DWORD dwRowSize ); Dest
> should be uncompressed and Src should be compressed.

That assumes you will always be decoding the entire image.  You need a
different interface if line-at-a-time decoding is or becomes a
requirement.

> Is there someone out there that has a special intrest in the tiff
> decoding ?

The roots of the libtiff g3/g4 decoder go back to my code in viewfax.

> I have ripped code out of libtiff but would like to get a
> clearer picture of what some of the variables is for in libtiff group
> 4 decoding.

Feel free to ask questions.  Note that the code was originally
developed in the era of 16MHz machines and the aim was to display
faxes at acceptable interactive rates, rather than maintainability or
understandability.

-- 
Frank Cringle,      fdc@cliwe.ping.de
voice: (+49 7745) 928759; fax: 928761

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