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On 09/05/2011 12:51 AM, Bruce Bannerman wrote:
<blockquote cite="mid:CA8A3E2B.B52C%25B.Bannerman@bom.gov.au"
type="cite">
<title>Re: [ELGIS] POLL: 12 bit JPEG compression in TIFF
[SEC=UNCLASSIFIED]</title>
<font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;">Peter,<br>
<br>
Sorry to labour this point.<br>
<br>
It will depend on how the end user wants to use the data.<br>
<br>
</span></font></blockquote>
I could't agree more.<br>
<blockquote cite="mid:CA8A3E2B.B52C%25B.Bannerman@bom.gov.au"
type="cite"><font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;">
If they want the data for analysis, via say an image
processing application, then anything that will degrade the
data should be discouraged. This includes compression via a
lossy format such as JPEG or ecw, MrSID, JPEG2000 etc.
Analysts will typically want to work with the numbers for each
‘colour’ band in the the imagery<br>
<br>
</span></font></blockquote>
What I am currently looking for is a reasonable format web mapping.
So speed and relative quality are definitly important, size not that
much (but uncompressed is too big).<br>
<blockquote cite="mid:CA8A3E2B.B52C%25B.Bannerman@bom.gov.au"
type="cite"><font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;">
If the user is just after the data as a visualisation backdrop
then the JPEG compression should be fine.<br>
<br>
<br>
For an rpm package, if the TIFF – JPEG compression is only
available as an option, then this should be fine.<br>
<br>
I wouldn’t like to see it set up as the default option though.<br>
<br>
</span></font></blockquote>
<blockquote cite="mid:CA8A3E2B.B52C%25B.Bannerman@bom.gov.au"
type="cite"><font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;">
Bruce Bannerman<br>
<br>
</span></font></blockquote>
Peter<br>
<blockquote cite="mid:CA8A3E2B.B52C%25B.Bannerman@bom.gov.au"
type="cite"><font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;">
<br>
On 2/09/11 11:23 PM, "Peter Hopfgartner" <<a
moz-do-not-send="true" href="peter.hopfgartner@r3-gis.com">peter.hopfgartner@r3-gis.com</a>>
wrote:<br>
<br>
</span></font>
<blockquote><font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;">In my current tests, image quality
is fine. Anyway, when trying to<br>
produce some maps from TIFF Orthophotos, with uncompressed
GeoTiffs 10<br>
maps took me 1.6 s, with JPEG-Compression the same maps were
done only<br>
after 53 s.<br>
<br>
Peter<br>
<br>
On 08/15/2011 11:35 AM, Micha Silver wrote:<br>
> Hi Bruce:<br>
><br>
> On Mon, 2011-08-15 at 09:53 +1000, Bruce Bannerman
wrote:<br>
>> Agreed.<br>
>><br>
>> JPEG is a lossy compression format.<br>
>><br>
> Yes, but when I tried the JPEG 12 bit compression, I
found that pixel<br>
> for pixel, it was almost exactly the same as the
original tiff.<br>
><br>
><br>
>> People who use tiff, typically want a lossless
format.<br>
>><br>
>> Therefore, I don’t see the need for a JPEG
compression of TIFF.<br>
>><br>
>> If I wanted a lossy compression, I’d typically go
for a wavelet<br>
>> compression format like ecw.<br>
> True, but I always get stuck with the restrictive
licensing of ECW.<br>
> And if jpeg 12bit gives a file size only double of the
ECW compression<br>
> ratio, with *nearly* lossless results, it becomes
interesting...<br>
><br>
>> Bruce Bannerman<br>
>><br>
>><br>
>> On 14/08/11 1:44 AM, "Peter Hopfgartner"<br>
>> <<a moz-do-not-send="true"
href="peter.hopfgartner@r3-gis.com">peter.hopfgartner@r3-gis.com</a>>
wrote:<br>
>><br>
>> --------Micha Silver<<a
moz-do-not-send="true" href="micha@arava.co.il">micha@arava.co.il</a>>
wrote--------<br>
>><br>
>> Subject: Re: [ELGIS] POLL: 12 bit JPEG
compression in TIFF<br>
>><br>
>> Date: 12.08.2011 12:12<br>
>><br>
>><br>
>><br>
>> >On Fri, 2011-08-12 at 11:50 +0200,
Mathieu Baudier wrote:<br>
>><br>
>> >> What about the compression rates
of the standard TIFF<br>
>> compressions?<br>
>><br>
>> >> (Already available)<br>
>><br>
>> ><br>
>><br>
>> >AFAIK, regular TIFF compression
(Packbits, or LZW and the<br>
>> like) only<br>
>><br>
>> >give about 20% compression. JPEG is
around 90-95%, ECW and<br>
>> MrSid even<br>
>><br>
>> >more, and JPEG 12-bit looks to be
about 85-90%.<br>
>><br>
>> ><br>
>><br>
>> Most standard TIFF compression schemas are
lossless (similar<br>
>> to gzip compression in PNG). They might
give great results<br>
>> when there are large areas with constant
values. They are not<br>
>> so performant for orthophotos, where, on
the other hand, some<br>
>> data loss might be acceptable.<br>
>><br>
>><br>
>><br>
>><br>
>><br>
>> >><br>
>><br>
>> >> On 12 Aug 2011 11:36, "Micha
Silver"<<a moz-do-not-send="true"
href="micha@arava.co.il">micha@arava.co.il</a>><br>
>> wrote:<br>
>><br>
>> >><br>
>><br>
>> >><br>
>><br>
>> >><br>
>><br>
>> >> On 02/08/2011 12:01, Peter
Hopfgartner wrote:<br>
>><br>
>> >> ><br>
>><br>
>> >> > On 08/02/2011 09:01 AM,
Mathieu Baudier wrote:<br>
>><br>
>> >> >>...<br>
>><br>
>> >><br>
>><br>
>> >> Hi Peter:<br>
>><br>
>> >><br>
>><br>
>> >> I did a quick (amateur) test of
jpeg 12 this morning and I<br>
>> must say I<br>
>><br>
>> >> was surprised with the results.
I started with a 1.4 GB<br>
>> tiff ortho<br>
>><br>
>> >> photo, which I also have as an
ECW image. The ECW is about<br>
>> 64MB.<br>
>><br>
>> >><br>
>><br>
>> >> I used the OSGeo4W installation
of gdal with the libjpeg<br>
>> that supports<br>
>><br>
>> >> 12 bit, and I made two
compressed tiffs. The regular jpeg<br>
>> compression<br>
>><br>
>> >> came down to about 75 MB, a bit
larger than the ECW, but<br>
>> it's quality<br>
>><br>
>> >> was a bit fuzzy with color
changes in the pixels. (Of<br>
>> course ECW is<br>
>><br>
>> >> also lossy, introducing changes
in the pixel coloring, but<br>
>> keeping<br>
>><br>
>> >> "sharpness").<br>
>><br>
>> >><br>
>><br>
>> >> The 12 bit jpeg-compressed tiff
came down to about 120 MB,<br>
>> only twice<br>
>><br>
>> >> the size of the ECW, but it was
almost indistinguishable<br>
>> from the<br>
>><br>
>> >> original tiff! Both in coloring
and sharpness. That was<br>
>> very<br>
>><br>
>> >> impressive, I must say.<br>
>><br>
>> >><br>
>><br>
>> >> I don't know where the jpeg2000
format is going (if<br>
>> anwhere). For now<br>
>><br>
>> >> this 12-bit jpeg compression
looks like an ideal<br>
>> alternative to<br>
>><br>
>> >> struggling with the closed ECW
format on one hand, or the<br>
>> unwieldy<br>
>><br>
>> >> file sizes of uncompressed tiff
on the other.<br>
>><br>
>> >><br>
>><br>
>> >><br>
>><br>
>> >> Best, Micha<br>
>><br>
>> >><br>
>><br>
>> >><br>
>><br>
>> >><br>
>><br>
>> >><br>
>><br>
>> >> > > Peter<br>
>><br>
>> >> > >
_______________________________________________<br>
>><br>
>> >> > > el mailing list<br>
>><br>
>> >> > > <a
moz-do-not-send="true" href="el@lists.osgeo.org">el@lists.osgeo.org</a>
...<br>
>><br>
>> >> ><br>
>><br>
>> >> > This mail was received via
Mail-SeCure System.<br>
>><br>
>> >> ><br>
>><br>
>><br>
>><br>
>> Peter<br>
>><br>
>><br>
>><br>
>> R3 GIS Srl - GmbH<br>
>><br>
>> <a moz-do-not-send="true"
href="http://www.r3-gis.com">http://www.r3-gis.com</a><br>
>><br>
>><br>
>><br>
>>
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</span></font></blockquote>
</blockquote>
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