On Wed, May 8, 2013 at 9:51 PM, Frank Warmerdam <warmer...@pobox.com> wrote:
> Andrea,
>
> I'm not currently a user of the grid coverage reader, but I might at some
> point. Skimming the proposal I was wondering:
>
> 1) Why you offer the getMetadataNames(coverage,...) and
> getMetadataValues(coverage,...) on GridCoverageReader instead of handling
> them on GridCoverage.
>
Mind, this is not part of the proposal, the API has been like that for
years, but reading the coverage with some backends
implies... actually reading the pixels.
The reader is thus also a way to get all the meta information without being
forced to read the coverage (which would result in the
client code doing some silly things like trying to read a 1x1 coverage in
an attempt not to read too much data)
>
> 2) Similarly, why is the new GridCoverage2DReader interface on
> GridCoverageReader instead of offering that interface on the GridCoverage.
>
Same as above.
>
> I'm guessing it is assumed the reader can provide some overall information
> cheaply while it is assumed that the read() operation returning a
> GridCoverage is expensive. But it *feels* like an awkward arrangement.
>
It's exactly like this. I don't see the awkward side though, if I want meta
information I normally don't need the data, and once I've read the data is
too late for some information anyways, such as getting the list of times
and elevation, once I have the coverage, which is a 2d flat object, those
are gone (some selection or mosaicking already took place)
Cheers
Andrea
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