[Gdal-dev] gdal_merge.py in c#

[Frank Warmerdam]

Suray Ph wrote:
> Hello,
> 
> I try to convert some commandline utilities, written in python, in c#.
> 
> I need help for gdal_merge.py. I found in this file a 'function' called
> 'raster_copy_with_nodata', could some one explain me how to convert this one,
> especialy band.ReadAsArray(...), Numeric.equal(...), Numeric.choose(...),
> band.WriteArray(...).
> 
> I searched for documentation about python, but didn't find the right one.
> 
> The final goal is to be able to merge different reprojected GTiff files, with
> black area, into one without black area.

Philippe,

These are Numeric Python methods and as such there is unlikely to be a
direct C# analog.  But if you can read back the image as an array in
C# you can just loop over the array, doing comparisons to the nodata
value, and overlaying where appropriate.

Basically, this script code:

     data_src = s_band.ReadAsArray( s_xoff, s_yoff, s_xsize, s_ysize,
                                    t_xsize, t_ysize )
     data_dst = t_band.ReadAsArray( t_xoff, t_yoff, t_xsize, t_ysize )

     nodata_test = Numeric.equal(data_src,nodata)
     to_write = Numeric.choose( nodata_test, (data_src, data_dst) )

     t_band.WriteArray( to_write, t_xoff, t_yoff )

means:

1) read the source and destination image data.

2) Where source image pixel is *not* equal to the nodata value, copy
    it into the destination image.

3) write the destination image back.

Best regards,
-- 
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