On Mon, Mar 8, 2010 at 5:42 PM, Pierre Racine
<pierre.rac...@sbf.ulaval.ca> wrote:
>
> >4.- Add default geotransform to GDAL empty dataset: {0.0, 1.0, 0.0, 0.0,
> >0.0,1.0 }; (I can't get
> >geotransform from WKT Raster Band)
>
> Why? You can get all the parameters with (in order):
> rt_raster_get_x_offset(), rt_raster_get_pixel_width(),
> rt_raster_get_x_rotation(), rt_raster_get_y_offset(),
> rt_raster_get_y_rotation(), rt_raster_get_pixel_height()...
Yes, I can. It was testing code. But you're right.
>
> >1.- I'm testing this code with really simple raster, and I'm confused. For
> >example:
> >* 2x2 32 bits signed int raster, with "1" in all cells. The result:
> >POLYGON((0 0, 0 2, 2 2, 2 0, 0
> >0)). I was expecting POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))
>
> The result is correct since the pixel size is 1, the raster dimension is 2x2
> and there is only one group of pixel sharing the same value.
Ok, Thanks for confirmation.
>
> >* the raster
> >from
> >http://trac.osgeo.org/postgis/attachment/wiki/WKTRaster/SpecificationWorking01/WKTRasterEnvelopeC
> >onvexHullAndShape.gif. The result:
> >POLYGON ((3 1,3 2,2 2,2 3,1 3,1 6,2 6,2 7,3 7,3 8,5 8,5 6,3 6,3 3,4 3,5 3,5
> >1,3 1))
> >POLYGON ((3 3,3 6,6 6,6 3,3 3))
> >POLYGON ((5 1,5 3,6 3,6 6,5 6,5 8,6 8,6 7,7 7,7 6,8 6,8 3,7 3,7 2,6 2,6 1,5
> >1))
> >POLYGON ((0 0,0 9,9 9,9 0,0 0),(6 7,6 8,3 8,3 7,2 7,2 6,1 6,1 3,2 3,2 2,3
> >2,3 1,6 1,6 2,7 2,7 3,8 3,8
> >6,7 6,7 7,6 7))
> >
> >Something strange here? Am I doing things right?
>
> It look good to me. What is wrong?
Mmm... ok, it may be only my impression.
>
> >2.- I'd like to store the pixel value in each polygon. Is a good idea to
> >create a field in the layer
> >to store pixel value?
>
> You are supposed to return the value for each polygon in a "wktgeomval set"
> as stated in the specs. This way the SQL caller can decide what to do with
> the value. Isn't that what you did?
Yes, I did this. The point is I was trying to label each polygon with
its pixel value (GDALPolygonize allows this). Then, in a loop, I get
all the features of the layer written by GDALPolygonize and store the
exported WKT polygon and the px value in a wktgeomval structure.
Sounds good?
>
> >3.- From a GDAL RasterBand, I can fetch the owning dataset handle
> >(GDALGetBandDataset).I think it
> >could be useful to get the WKT Raster handle from a WKT RasterBand too... Am
> >I right?
>
> rt_band_get_data()?
No, I mean getting the raster that contains this band, from the band
struct itself, like
GDALDatasetH GDALGetBandDataset(GDALRasterBandH hBand )
from GDAL C API
(or GDALRasterBand::GetDataset() from GDAL C++ API)
>
> Pierre
Thanks Pierre!
Jorge
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