I wish to add LZW (or very similar) compression to my game engine. I would like to know various ways in which this can be done legally. There are a few factors to consider: #1: LZW was covered by U.S. Patent 4,558,302 and U.S. Patent 4,814,746, but the former has already expired. The latter may or may not have expired. #2: Both patents are U. S. patents. This company is Japanese. On the other hand, we plan to market the engine in America (and Japan). #3: http://www.google.com/patents?vid=4814746 I am willing to change the algorithm in some way so that it is not described by that page, but is still able to open LZW-compressed files. The reasons I want to use LZW: #1: I designed my own compression routine. Then I studied other compression routines to determine if mine was generally worse or better, and to get ideas on how I could improve it. I discovered that my algorithm already had a name, which was LZW. And someone patented it already. If I were to have implemented my algorithm without having done this extra research, I would have violated the LZW patent without even knowing it. #2: Since it is my own idea, it goes without saying that it is the idea I understand best in the field of compression. I do not want to try to come up with a totally new idea with so little time in my schedule (though admittedly I do have another complete idea and one that is 50% complete). #3: Since it turns out my idea has already been well tested, my theory that it would give decent results has been confirmed, which makes me want to stick with it even more. Finally, if bypassing the patent is quite a burden, I wonder how I would go about getting permission to add the compression routine to my engine. L. Spiro

LZW is no longer patented. That said, it's not the best out there. If you want to add compression to your engine, just use the LZMA SDK. No reason to reinvent the wheel here.

Thank you for the information. I had wondered about the other patent but could not find an expiration date on it.

That solves all of my problems.
Unfortunately, I do have a reason to reinvent the wheel and will not be using any 3rd-party libraries, although your link is undoubtedly useful.


Thank you,
L. Spiro

Out of curiosity, what are those reasons? The LZMA library is pretty much the most lightweight library one could ask for.

Quote: Original post by Sneftel
Out of curiosity, what are those reasons? The LZMA library is pretty much the most lightweight library one could ask for.

The LGPL isn't the most lightweight licence though ;) Perhaps that's the reason for re-invention?
[edit]just realised that while 7-zip is LGPL, that SDK is "public domain"...

It's public domain, which is the most lightweight free-software license.