JPG speed /TIF speed

[Sean Gillies]

On Mar 27, 2006, at 1:43 AM, Rahkonen Jukka wrote:

> ________________________________
>
> Sean Gillies wrote:
>
>> You might look at ECW compression which is much faster and better
>> quality than jpeg.  But the typical advice is to simply use
>> uncompressed tiffs, internally tiled with overviews:
>
> Or why not to have a try with JPEG 2000 which is ISO standard and =
> behaves like other wavelett based formats like ECW and MrSID?  For  
> an =
> easy start you could try to compress for example 10 - 100 images to  
> JPEG =
> 2000 with compression ratio of around 1: 10 or even 1:20 and to  
> make a =
> tileindex for Mapserver. By the way, if you have ESRI world files,  
> they =
> must be named as .wld for tileindex. You should see both a rather  
> good =
> performance and 90 percent savings in disk space (actually more than =
> that, if you otherwise used overviews). It will mean more computing  
> for =
> the server because it must decompress JPEG 2000 streams first but =
> because of internal indexing of JPEG 2000 disk operations will be  
> fast =
> and difference in time needed for the whole process is not that big.
>
> One problem is that JPEG 2000 streams can be created literally in =
> millions of different ways, not all of them offering good spatially =
> random access to data. Therefore I think that using some ready made =
> application developed GIS in mind for compressing could be a good  
> start. =
> One alternative which should give good results is free ECW JPEG 2000 =
> Compressor 7.0 from ER Mapper, but for sure there are others as  
> well.  =
> You can use dgal_translate as well, but I have not used it myself  
> and I =
> can not suggest you any parameters. If you would like have a total =
> control on JPEG 2000 compression you can use kdu_compress executable =
> that can be downloaded from www.kakadusoftware.com . Because of  
> those =
> million of parameter combinations you might be a bit confused at the =
> beginning but these parameters have satisfied me with lossless =
> compression of  3-channel images of size 10000 by 10000 pixels:
>
> kdu_compress -i input.tif -o output.jp2 -rate - Clevels=3D7  
> Clayers=3D27 =
> Creversible=3Dyes Cycc=3Dno Cprecincts=3D{256,256},{128,128} =
> Corder=3DRPCL Cblk=3D{32,32} ORGgen_plt=3Dyes -cpu 0 -mem
>
> For lossy compression "-rate 2.4" instead of "-rate -" would yield  
> 1:10 =
> compressed JPEG 2000 image.
>
> It would be nice if someone, sometime would  make a study about most =
> suitable ways to perform JPEG 2000 compression for Mapserver.
>
> Regards,
>
> -Jukka Rahkonen-
>
> =20

Jukka,

Good points there, but you have misquoted me. I did not type the  
lines that you attributed to me.

Sean

---
Sean Gillies
http://zcologia.com