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Sujet : Algorithme de Compression de BMP en GIF |
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Le composant TGifImage de Anders Melander permet de creer des GIFs en utilisant une compression RLE (compatible LZW)... ca peut peut-etre t'aider a pondre un algo sans avoir a payer de licence a Unisys ;)
Extrait du fichier d'aide du composant :
Citation :
Description
Specifies the compression method used when saving the GIF.
The TGIFCompression values specifies which compression algorithm to use when saving GIF:
- gcLZW: Normal LZW compression. This is the compression algorithm normally used by GIFs. It yeilds the best compression ratio, but also requires a LZW license from Unisys.
- gcRLE: GIF compatible RLE compression. The GIF compatible RLE compression doesn't compress as good as LZW, but since the LZW algorithm is not used, no Unisys license is required. This only applies to the GIF writer. The GIF reader will always use LZW, so a LZW license is required if the application reads GIF files. GIF files saved with the RLE compression algorithm can be read by all GIF readers (such as web browsers).
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Extrait de la licence :
Citation :
LZW license
GIF (and thus TGIFImage) uses an adaption of the LZW compression algorithm for image compression. The LZW algorithm is patented by UNISYS. Unfortunately UNISYS requires royalty payment for all software that uses the LZW algorithm.
To avoid the use of the LZW algorithm for writing GIFs, TGIFImage can write GIFs using a LZW compatible RLE compression method. See the TGIFImage.Compression property for more information. There are conflicting opinions on whether a LZW license is required to read GIFs. Some patent lawyers are of the opinion that the LZW patent does not cover LZW decoders, but others disagree. If this matters to you, you should contact your own lawyer.
For information regarding UNISYS' view on the use of LZW in commercial software, please read the License Information on GIF and Other LZW-based Technologies . The UNISYS patent on the LZW algorithm may or may not apply to you depending on the laws of your country. Personally I have less than warm feelings for Unisys and their patent and I don't care if you have a license or not.
The LZW patent expires in 2004.
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