[gdal-dev] Implementing write support for GDAL driver

[jramm]

Thanks a lot
Thats useful and encouraging!
I have not implemented CreateCopy -. Ive not looked to closely at
gdal_translate, but if CreateCopy is not available will it fall back on
Create and the write methods or is this a likely cause of errors? From
first impressions it looks like CreateCopy is not entirely necessary -
mostly a shortcut when writing a whole dataset to another, but I've not
looked closely at it yet.




On 30 March 2016 at 16:36, Even Rouault-2 [via OSGeo.org] <
ml-node+s1560n5258858h47 at n6.nabble.com> wrote:

> Le mercredi 30 mars 2016 17:17:11, jramm a écrit :
>
> > Hi
> > I am implementing a write driver for the Vertical Mapper/Northwood Grid
> > format (NWT_GRD), which already has read support.
> > I have attached a diff of what I have got so far. Needless to say, it is
> > not complete or working :D.
> >
> > I'm looking for information on development, specifically:
> >
> > - Precisely what functions need to be implemented so the writing is
> fully
> > supported? (i.e. the minimum to be able to create a dataset from scratch
> > and write data to it using RasterIO).
>
> What you implemented in your patch looks good : IWriteBlock,
> SetGeoTransform,
> SetProjectionRef, Create.
> With that, you can have full "dynamic creation" (as named in
> http://gdal.org/gdal_drivertut.html#gdal_drivertut_creation ), thus
> allowing
> it to be used as the target of gdalwarp for example.
>
> > - Is there any info out there on debugging GDAL drivers? What is the
> > standard approach. Currently im trying to use 'gdal_translate' as a way
> in
> > to get it to do something so I can set some break points...perhaps
> writing
> > a little test program would be a better method.
>
> Using gdal_translate is a reasonable way to test & debug write support.
> When
> used without any particular arguments, it's mostly a wrapper of
> CreateCopy().
>
> > Which brings me to
> > - What standards are there for writing unit tests, test programs? I can
> see
> > a load of python under 'autotest' which im not familiar with. Are there
> any
> > guidelines on thise (the README is none too helpful).
>
> Not really. Generally looking at existing tests should give you a good
> idea of
> how to extend. The basic is to add a method that returns 'success' or
> 'fail'
> strings, and to add it to the gdaltest_list array.
>
> The gdaltest class has GDALTest() and testCreateCopy() methods that make
> it
> generally easy to test write support. Have a look at
> autotest/gdrivers/bt.py
> for example.
>
> I guess you found the existing tests for NWG_GRD are in
> autotest/gdrivers/nwt_grd.py
>
> >
> > Ive been over the driver implementation tutorial a number of times but
> info
> > on implementing write support is fairly scant. I'd happily add to this
> if I
> > can get this done..
> >
> > Thanks for any help
> > grddataset_diff.txt
> > <http://osgeo-org.1560.x6.nabble.com/file/n5258855/grddataset_diff.txt>
> >
> >
> >
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