What's the best OUTPUTFORMAT for ECW-files using WMS

[Fawcett, David]

Steven, 

When you say that the performance with tileindex is worse, is your test case that you are zoomed in to the point where you are only hitting one tile, or is it where you are zoomed out so that you have to now open and load many image files instead of just one?  

If it is the latter case, it is worth exploring the use of multiple layers for the same data.  Make them scale-dependent, so you only see one layer at a time.  Use an overview/generalized image for the 'zoomed out' scales and when the user is zoomed in to the point where they will only hit one or a few tiles, use the tileindexed layer.  

David.

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On Behalf Of Steven De Vriendt
Sent: Monday, April 23, 2007 11:52 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] What's the best OUTPUTFORMAT for ECW-files using WMS


Ok, back to square one then...I assumed that splitting my
image up in several tiles would speed things up but
with this info it seems like I'll have to get the best out of serving the original file (±390 meg).

On a side note, are WMS-images delivered on the same way like f.i. google maps, earth do that or should I say is Google Earth some sort of great WMS-client...sorry if this is not relevant to the original question, though it's interesting to know.

Thanks to all for your usefull info !

Steven


On 4/23/07, Frank Warmerdam <warmerdam at pobox.com> wrote:
> Steven De Vriendt wrote:
> > I have about 50 ECW-files which I like
> > to serve via WMS.
> >
> > I'm using following OUTPUTFORMAT:
> >
> > OUTPUTFORMAT
> > NAME PNG24
> > DRIVER "GD/PNG"
> > MIMETYPE "image/png"
> > EXTENSION PNG
> > FORMATOPTION "INTERLACE=OFF"
> > IMAGEMODE RGBA
> > TRANSPARENT ON
> > END
> >
> > Image quality is good, but the performance is not what I'd like it 
> > to be. Can anyone help me adjusting these parameters ?
>
> Steven,
>
> On issue is of course whether it is really the input or output that is 
> slowing things down.  PNG24 output is generally quite expensive 
> computationally and folks have often found JPEG better for 24bit 
> output.  JPEG also produces much smaller files which is generally 
> good.
>
> I'd add that each ECW that has to be opened and any imagery read from 
> will be expensive.  If you can it is better with ECW to make a single 
> large mosaic unless you know that views are constrained in such a way 
> that allmost all requests will only touch one file.
>
> 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
>
>