[Gdal-dev] two subjects - Katrina Good News and Request for VRT API VB6 binding

[Frank Warmerdam]

On 10/9/05, Gerald Buckmaster <buckmasterjunior at yahoo.com> wrote:
> Frank,
>
> I have created the GDAL VB App Dev group on Yahoo Groups and I am
> cross-posting.  I have looks at the tutorials as you suggested above, and
> loaded the gdalvbtest project to run.  Realizing I would need to understand
> the VRT before moving into saving out as Kakadu JP2, I wanted to see if I
> could read the attributes from a sample JP2 with the gdalvbtest project.  I
> found out that gdal12vb.dll doesn't have the JP2KAK driver built in.  Is it
> possible you could compile a gdal12vb.dll with the Kakadu driver?

Gerald,

My suggestion is to use FWTools 1.0.0a3 distribution which does
include the Kakadu driver.  The FWTools installer also installs the
VB6 bindings and attempts to update the GDAL DLL path appropriately.

> My strategy is to first determine what will go into the VRT XML.  Most of
> the items needed are already being generated by my code.  I am confused how
> the GDAL.Open() function will work with the XML.  Shouldn't it be more like
> CreateCopy()?  Even then, I really don't understand how the XML gets used
> unless something like SetGeoTransform() is involved.

Internally gdal_translate usually creates a virtual dataset, and then
calls CreateCopy() with that virtual dataset as the input datasource.
I am suggesting that you create an XML description of your virtual
datasource (doing subwindowing, etc) and pass that XML to GDAL.Open()
which will return a virtual datasource that you can pass as input to
CreateCopy().

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent