[gdal-dev] Can VRT be used to control display order of images in
mosaic?
Frank Warmerdam
warmerdam at pobox.com
Tue Jun 22 11:16:14 EDT 2010
Roger André wrote:
> Hi All,
>
> I'd like to control the order in which overlapping images are displayed
> in a mosaic. Is it possible to do that by using a VRT, and altering the
> order in which the files are defined in it?
>
> The online doc for gdalbuildvrt states, "If there is some amount of
> spatial overlapping between files, the order may depend on the order
> they are inserted in the VRT file, but this behaviour should not be
> relied on."
>
> Not sure if this disclaimer is for the gdalbuildvrt utility, or
> describes the generic behavior of a raster VRT.
Roger,
I believe the statement applies to the VRT format itself. I have looked
at the code, and it always applies them linearly based on the order they
appear in the .VRT list of sources. I think you could depend on it "for now"
though in a future version we might do something more fancy that would
result in alternate ordering.
Best regards,
--
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I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at pobox.com
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