| GIF compression support in ImageMagick - Re-Post [message #41638] |
Wed, 03 November 2004 22:26  |
Lince.Lawrence
Messages: 4
Registered: November 2004
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Junior Member |
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friends
As in this message. How can I enable LZW in ImageMagick? Where should
I alter the default option as advocated in the Quoted mail
"--enable-lzw (configuration switch)"
Currrently I am using ImageMagick to convert EPS to GIF by punchin in
the following command sequence in the command line:
convert -antialias -transparent white -colors 16 -compress LZW
eqn10.eps eqn10.gif
The output should come around 4K, whiile using the above command I get
a comparitively huge file of 20K. So I think the command "-compress
LZW" is not executed correctly (may be due to the disabled LZW option)
Kindly pour-in your valuable comments.
Thanks,
Lince M Lawrence
================================ Quote =============================
Yes, this is related (marginally) to IDL.
In the discussion on the lack of GIF support in IDL 5.4 a month or two
ago,
I said that ImageMagick (http://www.imagemagick.org/) was a good tool
for
creating GIFs. Although I have used ImageMagick for years I don't
create
GIFs very often. And I failed to notice that some time recently the
following comment has appeared in the README:
***
--enable-lzw (configuration switch)
Unisys reportedly claims a patent on the algorithm supporting LZW
compression (e.g. used by GIF and TIFF). To avoid possibly infringing
on
this patent, support for LZW is disabled by default. With LZW support,
GIF
files written by ImageMagick will be much larger than expected
***
This explains the enormous increase in size when I converted some
files from
PNG to GIF the other day!
So ImageMagick is not a good tool for creating GIFs (unless you go to
some
trouble to enable LZW compression) and IDL is not the only
organisation
abandoning GIF because of patent issues.
All the more reason to BURN ALL GIFS, I say.
BTW, ImageMagick can still *read* compressed GIFs.
---
Mark Hadfield
m.hadfield@niwa.cri.nz http://katipo.niwa.cri.nz/~hadfield
National Institute for Water and Atmospheric Research
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