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Posted by Stichting ST on February 24, 2005, 11:17 am
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>I don't know of any "direct" way to do it. You basically have to decompress
>the MrSid to a geoTiff, and then recompress it w/ the LizardTech
>application.
>
>Out of curiosity, why do you feel the MrSid format is better? Anecdotally,
>we (where I work) tested it in a few different places and ECW performed
>faster the MrSid in both our CAD and GIS applications and appears to give a
>sharper image... The ECW file sizes were slightly larger though, but not
>significantly. Additionally, ERMapper (makers of ECW) have free downloads
>for a compressor (500mb or less images) and viewer. I'm not a fan of
>LizardTech's browser plug-in. I liked their older GeoViewer better:-)
I can confirm some observations.
Both methods use basically the same technic (wavelet) and both give the same
kind of artifacts which high compressionrates.
When working with maps ecw is superior to MrSid, we have observed. Images are
sharper because lines are kept much better together in ecw.
Try for once a picture with text only. Then the difference is very clear
between the two.
When working with aireal colourphotographs differences are small between the
two.
And about processing power needed for reading/displaying: ecw is much faster
on an old slow notebook.
Comparision for Windows CE could not be made (no Mr.Sid) but ecw works with
this free available library: Trimble ECW Decompression SDK for Windows CE and
Pocket PC
http://www.ermapper.com/downloads/download_view.aspx?PRODUCT_VERSION_ID=202
Piet
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