AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

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.

nick.

>Nicholas Humfrey wrote:
>>
>>Hi,
>>
>>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...

Nick,

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

Thanks,

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

email njh@ecs.soton.ac.uk
www http://www.ecs.soton.ac.uk/~njh/