Loïc, this sounds sorta like what I was doing in my code poorly, which is why I turned to the command-line tools. Do you know whether any of the GDAL command-line tools can apply a majority filter with a large moving window?
Jack. -- mathuin at gmail dot com On Fri, Jan 27, 2012 at 12:05, Dutrieux, Loïc <loic.dutri...@wur.nl> wrote: > Hi John, > > If I may add a bit to the discussion, applying resampling algorithm other > than nearest neighbor to thematic layers such as land cover classification is > not really recommended. > However, if you want to smoothen the edges of your resampling output, I would > suggest a two steps approach: > - Resample using nearest neighbor. > - Apply a majority filter with a large moving window. > > I cannot guarantee the result, but I guess it should work. > > Best regards, > > Loïc > > -----Original Message----- > From: gdal-dev-boun...@lists.osgeo.org > [mailto:gdal-dev-boun...@lists.osgeo.org] On Behalf Of John Twilley > Sent: vendredi 27 janvier 2012 20:58 > To: Dmitry Baryshnikov > Cc: gdal-dev@lists.osgeo.org > Subject: Re: [gdal-dev] gdalwarp makes landcover files blocky when shrinking > pixel size > > None of those resampling methods are well-suited to classified rasters as far > as I can tell. > > The method that has worked best in the past was to take the majority of a > number of the nearest neighbors. The 'mode' algorithm in gdaladdo may do > that, but I haven't checked the source code. > > Jack. > -- > mathuin at gmail dot com > > > > 2012/1/27 Dmitry Baryshnikov <poli...@mail.ru>: >> 27.01.2012 23:30, John Twilley пишет: >> >>> Cubic is fine for the elevation, but it doesn't work on the landcover. >>> which is the problem I originally mentioned. >>> >>> Jack. >>> -- >>> mathuin at gmail dot com >>> >>> >>> >>> 2012/1/27 Dmitry Baryshnikov<poli...@mail.ru>: >>>> >>>> 27.01.2012 20:19, John Twilley пишет: >>>> >>>>> After retrieving the files and building VRTs from them, I run the >>>>> following gdalwarp commands: >>>>> >>>>> gdalwarp -q -multi -t_srs "+proj=aea +datum=NAD83 +lat_1=29.5 >>>>> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 >>>>> +-te >>>>> 2002944 2271744 2016768 2288640 \ >>>>> -srcnodata -340282346638528859811704183484516925440 -dstnodata 0 >>>>> ND302HT.vrt ND302HT.tif gdalwarp -q -multi -t_srs "+proj=aea >>>>> +datum=NAD83 +lat_1=29.5 >>>>> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 >>>>> +-te >>>>> 2002944 2271744 2016768 2288640 \ >>>>> -srcnodata 255 -dstnodata 11 L0102HT.vrt L0102HT.tif >>>>> >>>>> The only differences between the lines are the nodata values. >>>>> >>>>> Jack. >>>>> -- >>>>> mathuin at gmail dot com >>>>> >>>>> >>>>> >>>>> On Thu, Jan 26, 2012 at 22:49, Dmitry Baryshnikov<poli...@mail.ru> >>>>> wrote: >>>>>> >>>>>> 27.01.2012 3:39, John Twilley пишет: >>>>>>> >>>>>>> I am working with elevation and landcover data downloaded from >>>>>>> the USGS. I use gdalwarp to convert the data to a much smaller >>>>>>> pixel. The elevation data works very nicely with cubic >>>>>>> resampling, but the only resampling that works at all for the >>>>>>> landcover data is nearest-neighbor and that's very blocky. When >>>>>>> I last worked with landcover data, I used a majority algorithm >>>>>>> which produced smoother output -- but that algorithm is not implemented >>>>>>> in gdalwarp. >>>>>>> I am looking over the source to gdalwarp to see how hard it is to >>>>>>> add a new algorithm. Other than that, though, what options are >>>>>>> available to me? Thanks in advance! >>>>>>> Jack.-- >>>>>>> mathuin at gmail dot com >>>>>>> _______________________________________________ >>>>>>> gdal-dev mailing list >>>>>>> gdal-dev@lists.osgeo.org >>>>>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev >>>>>>> >>>>>>> >>>>>> Hi John, >>>>>> >>>>>> That is your command line string for gdalwarp? >>>>>> >>>>>> Best regards, >>>>>> Dmitry >>>>>> >>>>>> _______________________________________________ >>>>>> gdal-dev mailing list >>>>>> gdal-dev@lists.osgeo.org >>>>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev >>>> >>>> Hi John, >>>> >>>> Try to add "-r cubic" command parameter For example: >>>> >>>> >>>> gdalwarp -q -multi -t_srs "+proj=aea +datum=NAD83 +lat_1=29.5 >>>> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 -r cubic >>>> -te >>>> >>>> 2002944 2271744 2016768 2288640 \ >>>> -srcnodata -340282346638528859811704183484516925440 -dstnodata 0 >>>> ND302HT.vrt ND302HT.tif >>>> >>>> You can found additional parameters description here: >>>> http://www.gdal.org/gdalwarp.html >>>> I have tested -r parameter and it works. >>>> >>>> >>>> Best regards, >>>> Dmitry >>>> >>>> >>>> _______________________________________________ >>>> gdal-dev mailing list >>>> gdal-dev@lists.osgeo.org >>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev >>> >>> >> Hi John, >> You can use resampling methods: >> near: nearest neighbour resampling (default, fastest algorithm, worst >> interpolation quality). >> bilinear: bilinear resampling. >> cubic: cubic resampling. >> cubicspline: cubic spline resampling. >> lanczos: Lanczos windowed sinc resampling. >> >> And what method do you need? >> >> >> Best regards, >> Dmitry >> _______________________________________________ >> gdal-dev mailing list >> gdal-dev@lists.osgeo.org >> http://lists.osgeo.org/mailman/listinfo/gdal-dev > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev > _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
