🚀 go-pugleaf

Greg Cockroft writes
-> In article <1992Aug13.215318.530@ms.uky.edu> soward@slow.inslab.uky.edu  
-> (John Soward) writes:
-> > Glenn Reid writes
-> > -> the compressed data.  Just yesterday I got a 10-to-1 compression
-> > -> on a directory full of TIFF files, and I thought that TIFF already
-> > -> had reasonably good compression in its internal format!
-> > 
-> > 	No actually it sucks (e.g it has none)...unless you are using one  
-> of  
-> > NeXTs TIFF compression schemes...which are lempel-ziv (same as compress)  
-> or  
-> > JPEG (radically diferrent and results in a huge compression, but is  
-> "lossy" --  
-> > which sometimes is a big deal and sometimes is not).
-> > --
-> 
-> This is incorrect information.
	I do not think so...better read again for content.

-> TIFF 5.0 has optional compression of various types.
		^^^^^^^^
			This is the key....

->    LZW --   same as in compress. Previous substrings in a lookup table.
->    packbits --  run length encoding
->    group 4? fax compression. -- Various bit strings representing runs of
->                               0 and 1 bits. Some interline deltas.
-> 
-> NXImageBitImageRep supports LZW and packbits.
-> 
-> The JPEG data in 2.x TIFF files is a non-standard extension because it had  
-> not yet been addressed in TIFF when 2.0 shipped. JPEG will be part of TIFF  
-> 6.0.  3.0 NeXTStep is supposed to conform to TIFF 6.0.
	This is, however, claimed in the 3.0pr2 docs.
-> 
-> For the most part LZW and packbits do very well on non-continous tone  
-> images. Maybe not state of the art but certainly some big savings.

	In real-world usage, packbits seems to perform poorly, but lzw does  
okay--but not really much better than using compress (also lempel-ziv) on the  
tiff file (but then you have to actually issue uncompress to open it ;-)

--
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