On the fly conversion for compressed raster images

[Frank Warmerdam]

On 2/2/06, Vincent J. Troisi <Vincent.Troisi at colorado.edu> wrote:
> I have raster images in zip, gzip, and/or tar format. I want to render
> these files via an html
> application and provide WMS services using MapServer 4.6, having the
> application
> automatically unzip, untar, uncompress the raster on the fly and either
> convert
> to a geotiff or use some other utility to present a png, jpg, or other
> standard format
> to the WMS client or the MapServer browse application. Any ideas you have
> on an approach that will allow me to maintain the storage of the raster
> images
> in their current packaging (zip, gzip, tar, etc.)?

Vince,

There is no support in mapserver for this currently.  Depending
on how badly you want to do this, I can think of a couple
options.

 o Some operating systems have special filesystems that
    can make .zip files (and possibly .tar.gz) look like a
    subdirectory.  If you can get the operating system to do
    the work, it should be fine with MapServer.

 o It would be theoretically possible to implement a "special
    filesystem handler" in GDAL to address this but it would
    require some coding.  Once done it would still only work
    for file formats that work entirely through the "VSI*L" API.
    This is the same mechanism I use for memory based access
    to files with GDAL.   Let me know if you want to follow up
    on this option.

But ultimately your desire to operate from compressed archive
files just seems like a bad idea not work the headaches to make
it all work.

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