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<DIV dir=ltr align=left><SPAN class=901295817-26022008><FONT face=Arial
color=#0000ff size=2>JPEG 2000 is a method for encoding raster images, in such a
way that in the encoded version the image has special properties -- ability to
extact "down-sampled" versions (with data loss), ~2x space savings, etc -- while
still retaining all of the original data. You can read the ISO spec and
verify the math, if you wish, to prove the encodings are lossless, or
alternatively you can trust the experts on the ISO
committee.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=901295817-26022008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=901295817-26022008><FONT face=Arial
color=#0000ff size=2>One can optionally choose to throw away bits while doing
the encoding (or after), but that is outside the realm of the JP2 encoding spec
per se. Modulo metadata, you can't tell if the image has undergone lossy
compression or not.</FONT></SPAN></DIV>
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color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=901295817-26022008><FONT face=Arial
color=#0000ff size=2>Again, what format do you store your data in now, and what
"proof" do you use to show it is lossless? (Just to be sure: you do know
that the data that you receive from your satellite ground station is
not bit-for-bit identical with the data that comes off the sensor unit on the
satellite?)</FONT></SPAN></DIV>
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<DIV dir=ltr align=left><SPAN class=901295817-26022008><FONT face=Arial
color=#0000ff size=2>If you'd like to get me samples of your data, either
by FTP or CD, I'd be happy to encode them into JP2 format and point to some
decoders you can use yourself to verify the data is indeed lossless (modulo
metadata). Futhermore, h</FONT></SPAN><SPAN class=901295817-26022008><FONT
face=Arial color=#0000ff size=2>ere at LizardTech, we run regression
tests on hundreds of images of all different data types on multiple HW and
SW platforms on a 24x7 basis, and we'd be happy to include your data in our
regression suite.</FONT></SPAN></DIV>
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color=#0000ff size=2></FONT></SPAN><SPAN class=901295817-26022008><FONT
face=Arial color=#0000ff size=2></FONT></SPAN><SPAN
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size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=901295817-26022008><FONT face=Arial
color=#0000ff size=2>-mpg</FONT></SPAN></DIV>
<DIV><FONT face=Arial color=#0000ff size=2></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2></FONT><BR> </DIV>
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<FONT face=Tahoma size=2><B>From:</B> discuss-bounces@lists.osgeo.org
[mailto:discuss-bounces@lists.osgeo.org] <B>On Behalf Of
</B>Bruce.Bannerman@dpi.vic.gov.au<BR><B>Sent:</B> Monday, February 25, 2008
7:39 PM<BR><B>To:</B> OSGeo Discussions<BR><B>Subject:</B> RE: [OSGeo-Discuss]
'lossless' JPEG2000<BR></FONT><BR></DIV>
<DIV></DIV><BR><FONT face=sans-serif size=2>IMO:</FONT> <BR><BR><BR><FONT
face=sans-serif size=2>Michael,</FONT> <BR><BR><FONT face=sans-serif
size=2>Thanks for the comments on this thread.</FONT> <BR><BR><FONT
face=sans-serif size=2>I've had a couple of private emails expressing interest
in the outcome, so I'll continue this conversation in public, rather than
moving it offline.</FONT> <BR><BR><BR><FONT face=sans-serif size=2>One of the
problems that I have is that I understand that JPEG 2000 can be 'lossy' or
'non-lossy'.</FONT> <BR><BR><FONT face=sans-serif size=2>(Is there a way to
tell if a JPEG2000 file is lossy or not?)</FONT> <BR><BR><BR><FONT
face=sans-serif size=2>I don't pretend to understand the maths behind wavelet
compressions.</FONT> <BR><BR><FONT face=sans-serif size=2>I have also not seen
'proof' that would convince me I would be able to safely compress all of
my imagery using JPEG2000, (potentially) throw away my source imagery and feel
confident that I'd be able to run image processing routines on the radiometric
'numbers' of the imagery at some undefined point in the future with confidence
in the integrity of the results.</FONT> <BR><BR><FONT face=sans-serif
size=2>As a reminder, when talking about 'imagery', I'm using the term in its
broadest sense to include data such as multi and hyperspectral data in the
umbrella term 'imagery'. I'm not talking about only three bands displayed as
Red, Green and Blue, but **all** the bands in the 'file'.</FONT>
<BR><BR><BR><FONT face=sans-serif size=2>The description of a test that I
included in the early stages of this thread would give me a degree of
confidence that JPEG 2000 was a suitable format for long term archival of
image data.</FONT> <BR><BR><FONT face=sans-serif size=2>All that I'm seeing at
the moment from many people and organisations is something to the effect of
"Trust me, your data is saved using a loss-less compression."</FONT>
<BR><BR><BR><FONT face=sans-serif size=2>Bruce</FONT> <BR><BR><FONT
face=sans-serif size=2><BR></FONT><BR><BR><FONT
size=2><TT>discuss-bounces@lists.osgeo.org wrote on 26/02/2008 04:27:22
AM:<BR><BR>> Bruce-</TT></FONT> <BR><FONT size=2><TT>>
</TT></FONT> <BR><FONT size=2><TT>> Again, I'm not sure how to
convince you of this... JP2 is <BR>> inherently lossless just like
GeoTIFF is; what arguments do you / <BR>> would you find persuaive to use
GeoTIFF? (alternatively, what do <BR>> you use now that you
trust?)</TT></FONT> <BR><FONT size=2><TT>> </TT></FONT> <BR><FONT
size=2><TT>> [feel free to take this to private email, this is probably a
bit <BR>> esoteric for the rest of the OSGeo crowd]</TT></FONT> <BR><FONT
size=2><TT>> </TT></FONT> <BR><FONT size=2><TT>> -mpg</TT></FONT>
<BR><FONT size=2><TT>> </TT></FONT> <BR><FONT size=2><TT>>
<BR></TT></FONT><BR><BR><BR>
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