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<TITLE>Re: [ELGIS] POLL: 12 bit JPEG compression in TIFF [SEC=UNCLASSIFIED]</TITLE>
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<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>
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>
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>
Bruce Bannerman<BR>
<BR>
<BR>
On 2/09/11 11:23 PM, "Peter Hopfgartner" <<a 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 href="peter.hopfgartner@r3-gis.com">peter.hopfgartner@r3-gis.com</a>> wrote:<BR>
>><BR>
>> --------Micha Silver<<a 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 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 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 href="http://www.r3-gis.com">http://www.r3-gis.com</a><BR>
>><BR>
>><BR>
>><BR>
>> _______________________________________________<BR>
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>><BR>
>> This mail was received via Mail-SeCure System.<BR>
><BR>
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