[ELGIS] POLL: 12 bit JPEG compression in TIFF

[Peter Hopfgartner]

--------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 ...
>> > 
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>> > 

Peter
 
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