TIFF and LibTiff Mail List Archive


2002.10.10 01:03 "ExtraSamples = 999 in Corel TIFF", by Frank Warmerdam
2002.10.10 14:02 "Re: ExtraSamples = 999 in Corel TIFF", by Martí Maria
2002.10.24 12:00 "Re: 1:2 Compression ?", by
2002.10.24 11:49 "Re: {SPAM?} Re: 1:2 Compression ?", by Nicholas Humfrey

2002.10.24 11:49 "Re: {SPAM?} Re: 1:2 Compression ?", by Nicholas Humfrey

Looks like I was working too late last night!

The compression ratio was just a measure of how effective Packbits was being.

Not sure what I changed (or when) but it is compressing more efficiently now.

Sorry for the stupid question.


>Nicholas Humfrey wrote:
>>This is probably a stupid question but I have been hunting around
>>for quite a while and can't solve it. Had a look at the header
>>files and manual pages but no luck...
>>How do I enable basic 1:2 compression for a TIFF file - in addition
>>to the Image codec compression - such as Packbits.
>>I have two identical image files - one compressed using a graphics
>>program and one compressed using libtiff. When comparing using
>>tiffcmp - they it finds no differences.
>>However the libtiff file is twice the size of the graphics editor.
>>When I get information about the file I am told that although both
>>files are compressed using PackBits another field says that the
>>libtiff file is compressed 1:1 and the other file is compressed 1:2.
>>Is this an extension to TIFF that libtiff can't write? - I can
>>read/decode the compressed files fine...


I have never heard of this 1:2 business. Could you email me the smaller packbits file produced with the graphics program in question?


Nicholas Humfrey BSc
Intelligence, Agents, Multimedia Group
Dept of Electronics and Computer Science
University of Southampton UK