posted on 2006-06-06 22:32 david.turing 阅读(4526) 评论(4) 编辑 收藏 所属分类: 数字水印
在用数字水印处理GIF图片的时候，我往往有这样一个忧虑，因为GIF使用了LZW算法，而这个算法被Patent了，所以除非有这样的需求用Gif去生成数字水印,否则建议大家不要用GIF。 如果让我选择一种取代格式生成水印图片，我用PNG。 下面是一篇引述，来自GNU（为什么GNU网站上没有GIF图片） There are no GIFs on the GNU web site because of the patents (Unisys and IBM) covering the LZW compression algorithm which is used in making GIF files. These patents make it impossible to have free software to generate proper GIFs. They also apply to the compress program, which is why GNU does not use it or its format. Unisys and IBM both applied for patents in 1983. Unisys (and perhaps IBM) applied for these patents in a number of countries. Of the places whose patent databases we were able to search, the latest expiration date seems to be Friday 11 August 2006 1. Until then, anyone who releases a free program for making GIF files is likely to be sued. We don't know any reason to think that the patent owners would lose these lawsuits. If we released such a program, Unisys and IBM might think it wiser (for public relations reasons) not to sue a charity like the FSF. They could instead sue the users of the program, including the companies who redistribute GNU software. We feel it would not be responsible behavior for us to set up this situation. Many people think that Unisys has given permission for distributing free software to make GIF format. Unfortunately that is not what Unisys has actually done. Here is what Unisys actually said about the matter in 1995: ...... 1. We were able to search the patent databases of the USA, Canada, Japan, and the European Union. The Unisys patent expired on 20 June 2003 in the USA, in Europe it expired on 18 June 2004, in Japan patent expired on 20 June 2004 and in Canada it expired on 7 July 2004. The U.S. IBM patent expires 11 August 2006, (we are still searching the databases of other countries). 回复 更多评论
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