[ELGIS] POLL: 12 bit JPEG compression in TIFF [SEC=UNCLASSIFIED]

Hatzopoulos, Nikolaos hatzopou at chapman.edu
Tue Sep 6 13:11:32 EDT 2011


use the 8bit mapping

http://www.gdal.org/rgb2pct.html


--Nikos Hatzopoulos
________________________________
From: el-bounces at lists.osgeo.org [el-bounces at lists.osgeo.org] on behalf of Peter Hopfgartner [peter.hopfgartner at r3-gis.com]
Sent: Monday, September 05, 2011 2:21 AM
To: Bruce Bannerman
Cc: el at lists.osgeo.org
Subject: Re: [ELGIS] POLL: 12 bit JPEG compression in TIFF [SEC=UNCLASSIFIED]

On 09/05/2011 12:51 AM, Bruce Bannerman wrote:
Peter,

Sorry to labour this point.

It will depend on how the end user wants to use the data.

I could't agree more.
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

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).
If the user is just after the data as a visualisation backdrop then the JPEG compression should be fine.


For an rpm package, if the TIFF – JPEG compression is only available as an option, then this should be fine.

I wouldn’t like to see it set up as the default option though.

Bruce Bannerman

Peter

On 2/09/11 11:23 PM, "Peter Hopfgartner" <peter.hopfgartner at r3-gis.com<UrlBlockedError.aspx>> wrote:

In my current tests, image quality is fine. Anyway, when trying to
produce some maps from TIFF Orthophotos, with uncompressed GeoTiffs 10
maps took me 1.6 s, with JPEG-Compression the same maps were done only
after 53 s.

Peter

On 08/15/2011 11:35 AM, Micha Silver wrote:
> Hi Bruce:
>
> On Mon, 2011-08-15 at 09:53 +1000, Bruce Bannerman wrote:
>> Agreed.
>>
>> JPEG is a lossy compression format.
>>
> Yes, but when I tried the JPEG 12 bit compression, I found that pixel
> for pixel, it was almost exactly the same as the original tiff.
>
>
>> People who use tiff, typically want a lossless format.
>>
>> Therefore, I don’t see the need for a JPEG compression of TIFF.
>>
>> If I wanted a lossy compression, I’d typically go for a wavelet
>> compression format like ecw.
> True, but I always get stuck with the restrictive licensing of ECW.
> And if jpeg 12bit gives a file size only double of the ECW compression
> ratio, with *nearly* lossless results, it becomes interesting...
>
>> Bruce Bannerman
>>
>>
>> On 14/08/11 1:44 AM, "Peter Hopfgartner"
>> <peter.hopfgartner at r3-gis.com<UrlBlockedError.aspx>>  wrote:
>>
>>          --------Micha Silver<micha at arava.co.il<UrlBlockedError.aspx>>  wrote--------
>>
>>          Subject: Re: [ELGIS] POLL: 12 bit JPEG compression in TIFF
>>
>>          Date: 12.08.2011 12:12
>>
>>
>>
>>          >On Fri, 2011-08-12 at 11:50 +0200, Mathieu Baudier wrote:
>>
>>          >>  What about the compression rates of the standard TIFF
>>          compressions?
>>
>>          >>  (Already available)
>>
>>          >
>>
>>          >AFAIK, regular TIFF compression (Packbits, or LZW and the
>>          like) only
>>
>>          >give about 20% compression. JPEG is around 90-95%, ECW and
>>          MrSid even
>>
>>          >more, and JPEG 12-bit looks to be about 85-90%.
>>
>>          >
>>
>>          Most standard TIFF compression schemas are lossless (similar
>>          to gzip compression in PNG). They might give great results
>>          when there are large areas with constant values. They are not
>>          so performant for orthophotos, where, on the other hand, some
>>          data loss might be acceptable.
>>
>>
>>
>>
>>
>>          >>
>>
>>          >>  On 12 Aug 2011 11:36, "Micha Silver"<micha at arava.co.il<UrlBlockedError.aspx>>
>>          wrote:
>>
>>          >>
>>
>>          >>
>>
>>          >>
>>
>>          >>  On 02/08/2011 12:01, Peter Hopfgartner wrote:
>>
>>          >>  >
>>
>>          >>  >  On 08/02/2011 09:01 AM, Mathieu Baudier wrote:
>>
>>          >>  >>...
>>
>>          >>
>>
>>          >>  Hi Peter:
>>
>>          >>
>>
>>          >>  I did a quick (amateur) test of jpeg 12 this morning and I
>>          must say I
>>
>>          >>  was surprised with the results. I started with a 1.4 GB
>>          tiff ortho
>>
>>          >>  photo, which I also have as an ECW image. The ECW is about
>>          64MB.
>>
>>          >>
>>
>>          >>  I used the OSGeo4W installation of gdal with the libjpeg
>>          that supports
>>
>>          >>  12 bit, and I made two compressed tiffs. The regular jpeg
>>          compression
>>
>>          >>  came down to about 75 MB, a bit larger than the ECW, but
>>          it's quality
>>
>>          >>  was a bit fuzzy with color changes in the pixels. (Of
>>          course ECW is
>>
>>          >>  also lossy, introducing changes in the pixel coloring, but
>>          keeping
>>
>>          >>  "sharpness").
>>
>>          >>
>>
>>          >>  The 12 bit jpeg-compressed tiff came down to about 120 MB,
>>          only twice
>>
>>          >>  the size of the ECW, but it was almost indistinguishable
>>          from the
>>
>>          >>  original tiff! Both in coloring and sharpness. That was
>>          very
>>
>>          >>  impressive, I must say.
>>
>>          >>
>>
>>          >>  I don't know where the jpeg2000 format is going (if
>>          anwhere).  For now
>>
>>          >>  this 12-bit jpeg compression looks like an ideal
>>          alternative to
>>
>>          >>  struggling with the closed ECW format on one hand, or the
>>          unwieldy
>>
>>          >>  file sizes of uncompressed tiff on the other.
>>
>>          >>
>>
>>          >>
>>
>>          >>  Best, Micha
>>
>>          >>
>>
>>          >>
>>
>>          >>
>>
>>          >>
>>
>>          >>  >  >  Peter
>>
>>          >>  >  >  _______________________________________________
>>
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>>
>>          >>  >
>>
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>>
>>          >>  >
>>
>>
>>
>>          Peter
>>
>>
>>
>>          R3 GIS Srl - GmbH
>>
>>          http://www.r3-gis.com
>>
>>
>>
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