Fwd: Re: [gdal-dev] Creating a VRT dataset from overviews in C++

[Dmitry Baryshnikov]

-------- Исходное сообщение --------
Тема: 	Re: [gdal-dev] Creating a VRT dataset from overviews in C++
Дата: 	Thu, 10 May 2012 23:58:53 +0400
От: 	Dmitry Baryshnikov <polimax at mail.ru>
Кому: 	Thomas Sevaldrud <thomas at silentwings.no>



10.05.2012 23:14, Thomas Sevaldrud написал:
> Hi Dmitry, and thanks for your answer!
Hi Thomas!
>
> I was actually looking at this patch earlier today, but I also wanted 
> to see if I could solve it without patching.
>
> Will this patch be included in the official source?
My patch needs some refactoring and testing on python bindings. The work 
is going on , but not so fast as I wish. As I finished and commit my 
code, It'll be some testing period and than fixes will be accepted.
>
> Is it possible to do it the way I described in the previous mail?
Yes, you can try to warp and overview images (bands). You can get an 
overview of needed level from GDALRasterBand Class via GetOverview (int) 
method, but than you need to work on band basis and mixed them in colour 
image by yourself.
>
> Cheers,
> Thomas
>
> On Thu, May 10, 2012 at 7:11 PM, Dmitry Baryshnikov <polimax at mail.ru 
> <mailto:polimax at mail.ru>> wrote:
>
>     10.05.2012 19:03, tseval написал:
>>     Hi,
>>
>>     I'm trying to cut and reproject a large image with overviews using the c++
>>     api. This runs extremely slow when I produce highly downsampled cutouts
>>     covering large areas of the original image.
>>
>>     I understand the the Warp API doesn't use the overviews when resampling, so
>>     I wanted to make a temporary dataset from one of the downscaled overviews
>>     and do the warping on this dataset instead.
>>
>>     First of all, is this a sensible way of doing things? If so, what driver
>>     should I use? I guess VRT? I have been trying to create a VRT by doing
>>     something like this:
>>
>>     	double scaleX = (double)ovrW/origW;
>>     	double scaleY = (double)ovrH/origH;
>>     	GDALDataset* vrtDS = vrtDriver->Create("", ovrW, ovrH, _numBands,
>>     _dataType, NULL);
>>     	GDALSetProjection(vrtDS, _srcProjectionWKT);
>>     	double geoTransform[6];
>>     	srcDS->GetGeoTransform(geoTransform);
>>     	geoTransform[XFM_PIXEL_SIZE_EW] = scaleX*geoTransform[XFM_PIXEL_SIZE_EW];
>>     	geoTransform[XFM_PIXEL_SIZE_NS] = scaleY*geoTransform[XFM_PIXEL_SIZE_NS];
>>     	vrtDS->SetGeoTransform(geoTransform);
>>
>>     But how am I supposed to set the bands in the VRT from the downscaled
>>     overview bands in the original image?
>>
>>     Any help on this would be greatly appreciated :)
>>
>>
>>     --
>>     View this message in context:http://osgeo-org.1560.n6.nabble.com/Creating-a-VRT-dataset-from-overviews-in-C-tp4965891.html
>>     Sent from the GDAL - Dev mailing list archive at Nabble.com.
>>     _______________________________________________
>>     gdal-dev mailing list
>>     gdal-dev at lists.osgeo.org  <mailto:gdal-dev at lists.osgeo.org>
>>     http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>
>>
>     Hi,
>
>     You can try to use this patch to enable overviews in VRT
>     http://trac.osgeo.org/gdal/ticket/2076
>     or waits as I accomplish my work on fixing this
>     situation.<http://trac.osgeo.org/gdal/ticket/2076>
>
>     Best regards,
>         Dmitry
>
>     _______________________________________________
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>
>
Best regards,
     Dmitry

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