[gdal-dev] hdf5image metadata problems

Thu Jun 16 11:27:25 EDT 2011

Then, to keep consistency, the fact that hdf5imagedataset isn't consistent
with the hdf5dataset is a defect, right?
May I summarize the conclusions and update the ticket?

thanks for your patience Antonio
2011/6/16 Antonio Valentino <antonio.valentino at tiscali.it>

> Hi Alex,
>
> Il giorno Thu, 16 Jun 2011 11:51:48 -0300
> Alex Mantaut <alexmantaut at suremptec.com.ar> ha scritto:
>
> > Antonio,
> >            Ok, I understand the asociation between the raster band
> > and the metadata, but if you have to explicitally ask for the raster
> > band in order to get the metadata there is an inconsistency between
> > the interface to get metadata from hdf5dataset and
> > hdf5imagedataset... In hdf5dataset GetMetadata() returns the metadata
> > asociated to the all the subdatasets without need to explicitally ask
> > for the raster band, but in hdf5imagedataset you have to explicitally
> > ask for the raster band in order to get the metadata...
> >            IMHO the interface should be the same in both cases, in
> > that case hdf5imagedataset should retrieve the metadata asociated to
> > the subdataset directly via GetMetadata()...
>
>
> Umh, I don't know. I've always considered HDF5Dataset and
> HDF5ImageDataset as quite different things: the index and the chapters.
>
> But I have to admit that yours is a good point.
>
>
> > 2011/6/16 Antonio Valentino <antonio.valentino at tiscali.it>
> >
> > > Hi Alex,
> > >
> > > Il giorno Thu, 16 Jun 2011 10:05:42 -0300
> > > Alex Mantaut <alexmantaut at suremptec.com.ar> ha scritto:
> > >
> > > > Hi Antonio,
> > > >
> > > > For what I discussed with Frank it seemed that the expected
> > > > behavior was to get the only the data asociated to that
> > > > subdataset (plus some aditional data from root and the other
> > > > groups) I wasn't sure untill you confirmated...
> > > >
> > > > Well, right now when I open a specific subdataset it gets only the
> > > > raster band asociated to that dataset, but when I try to open the
> > > > metadata (with GetMetadata() or GetMetadataItem()) from that
> > > > subdataset it opens the metadata from all the groups (as expected)
> > > > but it doesn't get the metadata asociated to that subdataset...
> > > > Did I do something incorrectly when opening the metadata from the
> > > > subdataset?
> > > >
> > > >  The line suggested in the ticket:
> > > >         ReadGlobalAttributes( TRUE );
> > > >
> > > > Was a way to get around the problem, but now that I'm sure that
> > > > hdf5imagedataset doesn't need to read all the metadata, it's not a
> > > > suitable solution to the defect...
> > > >
> > > > Right now I found another way to get the metadata from the
> > > > subdataset, by getting the rasterband first, and then asking for
> > > > the metadata asociated to that raster band ( it seems a overly
> > > > convoluted to get the metadata asociated to that subdataset...)
> > > > I'm guessing that the expected behavior is to get the information
> > > > directly through GetMetadata() directly...
> > > >
> > > > regards
> > > >
> > >
> > > Well, IMHO it is not convoluted. Associating "HDF5 dataset" metadata
> > > tho the GDAL raster band just reflects the original HDF5 structure.
> > >
> > > Even if HDF5 and GDAL data model are quite different we can assume,
> > > IMHO, the following correspondence:
> > >
> > > HDF5 file    --> GDAL dataset (HDF5Dataset class)
> > > HDF5 Group   --> None (metadata are associated to GDAL dataset)
> > > HDF5 Dataset --> GDAL Raster Band
> > >
> > > HDF5 file can contain several datasets (with arbitrary shape) so the
> > > GDAL subdataset mechanism is used to tell to the HDF5ImageDataset
> > > class which is the "HDF5 dataset" the have to be mapped onto the
> > > GDAL raster band.
> > >
> > > I hope this is not too much confusing, with my poor english I'm not
> > > able to explain it better :).
> > >
> > >
> > > regards
> > >
> > > >
> > > > 2011/6/15 Antonio Valentino <antonio.valentino at tiscali.it>
> > > >
> > > > > Hi Frank, hi Alex,
> > > > >
> > > > > Il 15/06/2011 22:34, Frank Warmerdam ha scritto:
> > > > > > On 11-06-15 03:50 PM, Alex Mantaut wrote:
> > > > > >> Hi Frank:
> > > > > >>              Thanks for the swift reply.
> > > > > >>               Right now it opens the metadata asociated to
> > > > > >> the root, and also
> > > > > >> the metadata asociated with all the other groups, but it
> > > > > >> doesn't open
> > > > > the
> > > > > >> metadata asociated to the specified element (bug?)
> > > > > >
> > > > > > Alex,
> > > > > >
> > > > > > It sounds like a defect to me, yes.
> > > > > >
> > > > > > I would suggest filing a ticket that carefully documents the
> > > > > > problem with a supporting example file.
> > > > > >
> > > > > > Best regards,
> > > > >
> > > > > The current behavior looks fine to me.
> > > > >
> > > > > If one opens a specific subdataset then only one "HDF5 dataset
> > > > > object" can be accessed and it is mapped on GDAL raster bans n.
> > > > > 1. All other "HDF5 dataset object" in the h5 file are ignored
> > > > > by the HDF5ImageDataset so there is no reason IMHO to make
> > > > > their metadata available in some manner.
> > > > >
> > > > > Metadata associated to all HDF5 groups (including the root one)
> > > > > are available in any case and accessible via GDAL dataset
> > > > > metadata.
> > > > >
> > > > > my two cents
>
>
> --
> Antonio Valentino
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