Free GIF graphics driver for GCG (8.1)

mathog at seqaxp.bio.caltech.edu mathog at seqaxp.bio.caltech.edu
Sat Dec 18 00:13:35 EST 1999

In article <subwvqd1ec1.fsf at europa.sanger.ac.uk>, Peter Rice <pmr at sanger.ac.uk> writes:
>mathog at seqaxp.bio.caltech.edu writes:
>> This directory contains my GIF driver for GCG 8.1.  The driver is based on
>> GD 1.3 by Thomas Boutell.  It has been tested on OpenVMS but should work
>> correctly on Unix too.  However, since I don't have a GCG Unix system I
>> can't provide installation instructions for that.  Note also that the 
>> graphics driver on VMS is compiled using /STANDARD=VAXC because it breaks
>> in the parts provided by GCG without it.  You will likely have to use an
>> equally sloppy compiler mode on Unix. For instance, what "cc" with no args
>> will give you. 
>What is the current status of the GD library and the GIF patent?

Current GD versions generate PNG and not GIFS.  The version I used has
"miGIF" compression which is claimed by its author not to violate the LZW
patent.  It does run length encoding instead, which works pretty well 
on GCG graphics, which tend to have huge swatches of white space.  

>http://www.boutell.com/gd/ now only offers a GIF-free version of the
>GD library (1.7.3) and says GIF support was removed in version 1.6
>even though non-LZW GIF support was introduced in the 1.3 version you
>used. It also states that GIF versions are not currently available.

All that's correct - but I found the older version of GD elsewhere.

If you want to convert the GCG GIF driver to a PNG driver it should be
possible - take a look at how GIF.C is constructed.  PNG would be a bit
more involved though because you need a couple of extra libraries and not
just the GD bits. 

The advantage of going with GIF is that every single graphics program can 
handle it.  PNG works in current browsers but not older graphics programs.

If Unisys comes calling and provides evidence that miGIF violates LZW's
patents I'll rewrite the driver to output TIFF or JPEG.  Honestly, I don't 
think that would take more than a couple of days.  In the meantime, we'll 
keep using this GIF driver.


David Mathog
mathog at seqaxp.bio.caltech.edu
Manager, sequence analysis facility, biology division, Caltech 

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