LZW Lossy or Lossless???greenspun.com : LUSENET : PosterShop Talk : One Thread
Does anybody know if an LZW compressed tiff file has any degradation over an original tiff file. How does LZW render a much smaller file?
-- Anonymous, October 27, 1999
File reduction is greatest on images containing large area of flat (same) color, file size reduction is less on images that contain a wide range of different values. Every seminar I have attended, or book I have read, says that LZW compression is lossless. Mathematical algorithms are used to compress the number of bytes that are of the same value, rather than "000000000011111111", you get: "(10)0(8)1." Same information is less space, Quark Xpress sometimes will not display or print an LZW compressed file, giving you a streaked dark muddy blob, on screen or on paper. Quark denies that this problems exists, and it probably only occurs with the large files required for large format printing. I have read on-line that others have experienced the same problem, and there is a special extension to deal with this issue, I don't know who offers this extension.
Hope this helps.
-- Anonymous, November 05, 1999