I need the ability to be able to display ECW and JPEG2000 format files within MapServer via a Community Mapbuilder client which sends WMS requests for the images to MapServer

[John Mitchell]

Frank,

So if I have the ECW image compressed at a 2:1 ratio mapserver will process
it faster than if I have the ECW image at 20:1 because mapserver has to
decompress the image first.  Also the resulting image should be better since
I have not compressed it as much.

If I choose to have FORMATOPTION "TARGET=0" which means no compression then
my image quality will be better, but it will be slower to download since it
is not compressed?

John

On 11/30/06, Frank Warmerdam <warmerdam at pobox.com> wrote:
>
> John Mitchell wrote:
> > Frank,
> >
> > The ECW is already in a compressed format, so this means that the image
> > is compressed another 95%?  This additional compression is for
> > performance purposes?; does it affect the image quality?
>
> John,
>
> The imagery is decompressed within mapserver for rendering purposes, and
> then (if output is to ecw) re-compressed.  So the 95% is relative to
> uncompressed form, not cumulative.   Even if the original image was
> at 95% compression the process of decompressing and recompressing can
> result
> in additional image damage.
>
> Best regards,
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | President OSGeo, http://osgeo.org
>
>


-- 
John J. Mitchell
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