On 25 November 2014 at 05:34, Even Rouault <[email protected]> wrote: >> Otherwise I have not much to say about this RFC. "Blurring" has two r's, > > Fixed
Gaussian blur also has another complexity, since it's output dimensions depend on the fftconvolve mode (using scipy.signal docs http://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.signal.fftconvolve.html). For example, to "blur" a DTM and maintain the same output dimensions and geotransform, the mode would need to use a 'valid' convolution with a padded input array. This padded array would also have a mode (similarly from numpy docs http://docs.scipy.org/doc/numpy/reference/generated/numpy.pad.html), such as 'symmetric'. http://gis.stackexchange.com/a/10467/1872 Someone else may want to blur a DTM without using a padded array, and just return a smaller array with modified geotransform. And a different "blur" would expand the output dimension and modify the geotransform using a 'full' fftconvolve mode, using a 'constant'=0 padded array. An example of this is to "blur" a polygon that barely extends to the shape's extent, but maintain the blur beyond the initial extent. The constant value would also need to be supplied, as a value of 0 for numpy is default. http://gis.stackexchange.com/a/104338/1872 So in summary, I'm not sure how GDAL could best cover all combinations of padding and convolution modes, except to offer a few prepared use-cases, or somehow provide extra parameters. Or just provide a single use case, similar to Gaussian blur routines in various raster editing software. -Mike _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
