g3togif (was: web fax viewer...)

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About the issue of web fax viewer...

the solution of sending the g3 file as image/g3fax, and spawn a viewer
at the client side (e.g. viewfax) is certainly the best solution from
the technical point of view, since viewfax is fast and easy to use. I
am not sure if there is something comparable to viewfax (in terms of
speed and ease of use) on the Windows side.

The conversion from g3 to gif using g3topbm |ppmtogif is rather
slow, although in some cases it produces reasonably small files.
The speed problem can be solved pretty easily by writing a simple
g3togif program. The biggest problem I see is that fax are pretty
large (some 1700x2220 pixels) and usually do not fit within a page.
Shrinking to half resolution but still in 2 colors is somewhat
unsatisfactorily because it produces some unpleasant artifacts
(although files become usually smaller than the corresponding g3
files, at least in my tests with up to ~50KB files).

I think the best results could be achieved by producing a gif file
with about 100dpi on each direction and using antialiasing when
scaling down (i.e the resulting file could have 3-4 grey levels).
Any suggestion on which pipeline of pbm tools can do this (so as
to test how big the gif file would be, and if it is worthwhile to
write a standalone converter) ?

If this proves satisfactory, I suppose even the conversion can be done
on the fly without too much concern; I do not belive a fax page is
going to get hundreds of hit per day :) .

	Cheers
	Luigi
-----------------------------+--------------------------------------
Luigi Rizzo   | Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it | Universita' di Pisa
tel: +39-50-568533   | via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522   | http://www.iet.unipi.it/~luigi/
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