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The link below has came to my attention.


This page is owned by Unisys and among other things it says:

reading and/or writing of GIF images requires a license 
to use Unisys patented Lempel Ziv Welch (LZW) data 
compression and decompression technology, including United 
States Patent No. 4,558,302, Japanese Patent Numbers 
2,123,602 and 2,610,084, and patents in Canada, France, 
Germany, Italy and the United Kingdom.

Linrad uses a subroutine written by Sverre H. Huseby to
create screen dumps.

As far as I understand this makes it illegal to use Linrad
to save screen dumps in any of the following countries:

United States 
United Kingdom

This is of course a very unfortunate situation. The obvious
solution is to skip the GIF files and make Linrad write PNG
files. See http://burnallgifs.org/

Is there anyone on this list who knows people at Unisys?
Would they permit free use of .GIFs by radio amateurs for saving
screen dumps? The above link suggests they will not...

As far as I understand the PNG files are better than the GIF files
and they are supported by web browsers. PNG is open source. 

Replacing the gifsave routine by the corresponding routine(s)
from libpng should be straightforward but doing it by including
everything would double the source code size of Linrad. I am 
sure only a small fraction is needed, Linrad always saves
images with a small palette with 3 x 8 bits for each of the
perhaps 30 colours.

I have failed to download the source file. I am on a silly
Windows 2000 system for Internet access (It is me being silly

Is there anyone who would be interested to do the work to
replace GIFs by PNG files for the future use in Linrad?

Everything is in the file gifsave.c in Linrad. A file to replace
it and perhaps a package of other files to add to Linrad source.

Many thanks to Maggie, K3XS for posting the below link at


Leif  /  SM5BSZ