[OSGeo-Discuss] 'lossless' JPEG2000

[Bruce.Bannerman at dpi.vic.gov.au]

IMO:


Michael,

My concern as a custodian of significant image resources is to ensure that 
the integrity of this data is protected and available for future 
analytical use by ourselves and by the public.

As an example, to conduct multi-temporal analysis of 'imagery' to help 
understand big picture issues such as climate change.




I understand that wavelet compressions such as MrSid and ecw are lossy 
compressions and JPEG 2000 can be 'lossless', or as often occurs, lossy.



I'm currently seeing proposals to the effect:

- wrt imagery, most people only want to look at pretty pictures

- therefore we'll compress our imagery via wavelet compression and save a 
lot of disk space and ongoing SAN costs by backing up the source imagery 
to tape. Noone uses it anyway.



I've been around long enough to expect problems from tape backups, and to 
not expect my data to be there when I request a restore.

I can also see an increasing need for image analysis for big picture 
issues such as climate change and water shortage (in Australia).


Therefore, naiave as it is, I want to be 'convinced' that our data is 
protected for future use before agreeing to such potentially irreversible 
proposals.



Bruce




discuss-bounces at lists.osgeo.org wrote on 24/02/2008 08:44:25 AM:

> Bruce-
> 
> It is not clear to me what sort of "study" you would need to 
> convince you, as the ISO standard for encoding data into the 
> JPEG-2000 file format is by construction mathematically and 
> numerically lossless process.  (Indeed, "compression", i.e. throwing
> away bits so as to further reduce storage requirements, is actually 
> not defined within the scope of the standard.)
> 
> -mpg
> 


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