ecw files

[Frank Warmerdam]

On 10/26/05, Kevin Flanders <kevin at peoplegis.com> wrote:
>
> I am using ecw files (and sid files) on a few projects, and am wondering...
>
> 1.  does mapserver have to decompress these files to use them?

Kevin,

Only selected portions of the source file are extracted
and then used to assemble the image for the area of
interest.  The whole file is not decompressed.

> 2.  if so, are files compressed at 20:1 ratios faster than files compressed
> at 100:1 ?

I would actually *expect* 100:1 images decompress faster
since less data needs to be read from disk, but I haven't
verified this.

> 3.  Does anyone have info on the performance of sid files
> compared to ecw files?

I haven't done a good comparison, but experience I
has suggest they are at least roughly similar in speed.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent