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Re: [hylafax-users] 2D encoding



On 2003.10.19 08:15 Steve Underwood wrote:
Hi all,

Looking at the source code for HylaFAX it seems that 2D encoding isn't really supported.

It depends on what you mean. HylaFAX uses Ghostscript and libtiff to prepare documents for outbound transmission, and both adequately encode 2-D lines for use in both MR (partial 2-D) and MMR (full 2-D) images. HylaFAX can send such images just fine. However, HylaFAX's own TIFF encoder which is primarily used to image the tagline onto the outbound images only does 1-D encoding. That's why no taglines are imaged on MMR documents yet... the encoder needs some enhancement... but this shouldn't cause anyone to say that HylaFAX doesn't support 2-D MR or 2-D MMR, because it does.


Although 2D is an option, it seems to be a fake, using 1D coding in reality.

I assume you refer to the tagline imaging function that I mentioned already.


Since libtiff appears to do 2D coding properly, the 2D infrastructure seems to exist.

libtiff doesn't provide any memory-only encoder/decoder functions as far as I'm aware. So we can decode it from a filesystem or encode it to a filesystem, but we cannot do those from or to memory, thus HylaFAX must have its own encoder and decoder for memory functions. The decoder came from the same source as libtiff's (Frank Cringle's viewfax), so it was easy to keep updated by comparing with libtiff sources. The encoder seems to be unique to HylaFAX... at least it didn't seem to compare well to libtiff's encoder when I last looked.


Is it something that has just not been finished, or is there some solid reason for not doing full 2D encoding.

The encoder for tagline imaging could most certainly use some enhancement, and contributions are welcom ;-)


Lee.

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