[postgis-devel] [PostGIS] #2122: [raster] Real extent feature lost after metadata as views

[Mateusz Loskot]

On 3 December 2012 17:13, Pierre Racine <Pierre.Racine at sbf.ulaval.ca> wrote:
>
> Let's get back to the beginning:
>
> 1) Do we need the extent to reflect the original size of the raster because:
>
> a) It is necessary to implement optimized reading of the raster as a regularly blocked raster
>
> or
>
> b) Just to remember the original size of the raster

The extent is needed to perform correct reading and optimised way too
and to correctly process raster tiles which have been padded.
At the moment, there is no way to determine, if padding is present
and if it is, how much padding is present.

Remembering the original size of the raster is not needed
as for the sake of remembering it, but if available, it would be
considered as a mean to achieve the above (determine padding, etc.)

current size - original size = padding

if padding > 0
...
else
...

The same could be achieved having the real (original) spatial extent
in hand, that excludes the padding.
It does not matter if we operate in pixel space of the world coordinates space
here, as we can easily move between these two spaces.

The objective is to make loading and storage lossless, regardless of processing
at loading time (arbitrary tiling, padding). ATM, it is lossy.

Best regards,
--
Mateusz Loskot, http://mateusz.loskot.net