[mapguide-users] MrSID files through GDAL FDO provider

[Martin Morrison]

I would agree with the "hints" file might be a good avenue to approach.
I will say that ANY improvement in speed needs to be considered simply
because in larger map implementations a slight improvement in speed adds
up to large gains.

Martin

-----Original Message-----
From: mapguide-users-bounces at lists.osgeo.org
[mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Kenneth,
GEOGRAF A/S
Sent: Thursday, June 14, 2007 12:22 PM
To: MapGuide Users Mail List
Subject: Re: [mapguide-users] MrSID files through GDAL FDO provider

I looked at the way the providers are registered and tested in the GDAL 
library.
I think it would be a relatively small addition, to be able to provide 
"hints" to the driver.

The current problem is the Open() call, which tests the providers in
turn.
If there was a file in the folder (say "GDAL Loader Hints.txt" stating
ea.:
MrSID
ECW

The provider could try these first. It is of course also an overhead, 
but testing for a file's existence should be
a relatively low cost operation. Actually reading and parsing the files 
should be faster than the current
probing. I would recommend that this would be a hint only, and that the 
library should try all providers,
if none of the hinted providers succeed.

Regards, Kenneth, GEOGRAF A/S



Frank Warmerdam skrev:
> Martin Morrison wrote:
>> If the mapguide tries each provider in order to open an image, how
much
>> performance gain is there by only using one raster format and
compiling
>> only that driver?  Or can you specify the order in which the drivers
are
>> polled?
>
> Martin,
>
> There would be no appreciable improvement in performance - at least
> for files that actually open.  The case that the "test each in
sequence"
> thing tends to get inefficient is for files that fail to open because 
> then
> all the drivers are tested.  And there are sometimes a few drivers at
the
> bottom of the list that are somewhat expensive.  For instance, probing

> for
> header files and such.
>
> It is possible to only register required drivers but I think this is a
> relatively pointless optimization in the grand scheme of things.
>
> Best regards,
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