[ELGIS] POLL: 12 bit JPEG compression in TIFF

[Micha Silver]

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%.

> 
> 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 
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