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

[Micha Silver]

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> wrote:
> 
>         --------Micha Silver <micha at arava.co.il> 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>
>         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
>         
>         >> > > _______________________________________________
>         
>         >> > > el mailing list
>         
>         >> > > el at lists.osgeo.org ...
>         
>         >> >
>         
>         >> > This mail was received via Mail-SeCure System.
>         
>         >> >
>         
>         
>         
>         Peter
>         
>         
>         
>         R3 GIS Srl - GmbH
>         
>         http://www.r3-gis.com
>         
>         
>         
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