[gdal-dev] ReadAsArray

[Yuta Sato]

Thank you very much "Even Rouault" for making me understood.

On Fri, Apr 3, 2015 at 8:13 PM, Even Rouault <even.rouault at spatialys.com>
wrote:

> Le vendredi 03 avril 2015 12:46:48, Yuta Sato a écrit :
> > Dear Even Rouault:
> >
> > Thank you very much.
> > What about setting these parameters "used with .ReadAsArray()", though I
> > did not know their meanings?
> > buf_xsize=None, buf_ysize=None, buf_obj=None
>
> (Please keep the list CC'ed)
>
> buf_xsize and buf_ysize are the equivalents of nBufXSize and nBufYSize in
> GDALRasterBand::RasterIO()
> http://gdal.org/classGDALRasterBand.html#a75d4af97b3436a4e79d9759eedf89af4
> i.e. to do downsampling or upsampling of original data.
>
> buf_obj can be used to "recycle" an existing numpy array of the appropriate
> size instead of allocating a new one.
>
> >
> >
> > On Fri, Apr 3, 2015 at 7:43 PM, Even Rouault <even.rouault at spatialys.com
> >
> >
> > wrote:
> > > Le vendredi 03 avril 2015 12:22:00, Yuta Sato a écrit :
> > > > Dear Respected GDAL Developers and Users:
> > > >
> > > > What parameters should I set beforehand in order to accelerate the
> > >
> > > reading
> > >
> > > > of a GeoTiff file?
> > > >
> > > > I am using as follows:
> > > >
> > > > data =
> src_dataset.GetRasterBand(1).ReadAsArray(xoff,yoff,xsize,ysize)
> > > >
> > > > Does setting the following parameters accelerate?
> > > >
> > > > GDAL_CACHEMAX, GDAL_SWATH_SIZE
> > > >
> > > > I'm using gdal python.
> > >
> > > Yuta,
> > >
> > > Increasing GDAL_CACHEMAX might accelerate in case of repeated reads on
> > > windows
> > > that are identical or overlapping already read windows. Or if the way
> you
> > > read
> > > the raster doesn't follow its block shape : for example if the raster
> is
> > > organized by lines/strips and you read by square blocks, or the reverse
> > > situation.
> > >
> > > GDAL_SWATH_SIZE is only used by CreateCopy().
> > >
> > > Even
> > >
> > > --
> > > Spatialys - Geospatial professional services
> > > http://www.spatialys.com
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
>
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