[gdal-dev] Amplitude virtual bands for complex datasets ?

[Julien Michel]

Hi,

Started the work here :

https://github.com/OSGeo/gdal/compare/trunk...jmichel-otb:enhance-complex-datasets

For now, recognizes the following syntax :

gdal_translate -srcwin 1000 1000 1000 1000 
DERIVED_SUBDATASET:COMPLEX_AMPLITUDE:s1a-s6-slc-vv-20150619t195043-20150619t195101-006447-00887d-001.tiff 
~/tmp/test.tif

I need to see about exposing those derived datasets properly.

Antonio, I copied one of your pixel function for fast prototyping, I 
hope you do not mind. Of course upon completion of this work we should 
merge properly all your pixel functions with proper 
credits/copyright/licence. Thing is I did not know where to put them 
within gdal.

Regards,

Julien

Le 04/07/2016 à 11:06, Even Rouault a écrit :
> Hi,
>> To check if I understood well :
>>
>> I will create a driver that will recognize the
>> "DERIVED_SUBDATASET:Amplitude:original_datasetname" syntax. This driver
>> needs to now if "original_datasetname" is of complex type (to report it
>> can open it)
> That or we could also possibly accept non-complex types (assume imaginary part
> = 0). Antonio's functions handle complex & non-complex AFAICS
>
>> , and will also expose the derived band somehow (can I
>> benefit from the CreateDerivedBand API,
> If you write it, yes... (it doesn't exist yet if I wasn't clear)
>
> If you follow the VRT pixel function road, that's a matter of building a on-
> the-fly VRT dataset.
>
> http://www.gdal.org/gdal_vrttut.html#gdal_vrttut_creation could possibly be
> used. But AFAICS setting the pixel function name isn't supported. Could be
> done by implementing CPLErr VRTSourcedRasterBand::SetMetadataItem( const char
> *pszName, const char *pszValue, const char *pszDomain ), similarly to what
> VRTSourcedRasterBand::SetMetadataItem(...) handles for vrt sources.
>
>> and the pixel functions from Antonio ?).
> Would make sense to internalize this code (uses X/MIT license)
>
>> Also, "original_datasetname" can be a subdataset itself.
> Yes, that shouldn't matter to the driver. It is just a string that it provides
> to GDALOpen() (some care must be taken when parsing
> DERIVED_SUBDATASET:algname:original_datasetname, since original_datasetname
> can have columns too)
>
>> There should also be a mechanism that will report the existing
>> DERIVED_SUBDATASETS upon query (this I did not get yet).
> Implement in GDALDataset, the following method (from GDALMajorObject)
>
> virtual char **GetMetadata( const char * pszDomain = "" );
>
> char **GDALDataset::GetMetadata( const char * pszDomain = "" )
> {
> 	if( pszDomain != NULL && EQUAL(pszDomain, "DERIVED_SUBDATASET") )
> 	{
> 		// some stuff. Be careful that ownership of returned char** belongs
> 		// to the dataset object
> 	}
> 	else
> 		return GDALMajorObject::GetMetadata(pszDomain);
> }
>
> As well as :
>
> virtual char **GetMetadataDomainList(); to report DERIVED_SUBDATASET when it
> makes sense (contrary to GetMetadata(), ownership of the returned char**
> belongs to the caller)
>
> Even
>


-- 
Julien MICHEL
CNES - DCT/SI/AP - BPI 1219
18, avenue Edouard Belin
31401 Toulouse Cedex 09 - France
Tel: +33 561 282 894 - Fax: +33 561 283 109