Thanks Even However if I do the same thing with reprojection I get the same result. gdalwarp output looks sharp and ugly, imagemagick output looks nice.
Is there any way to force the bilinear/cubic interpolation to notice more pixels? The other interpolation methods are much slower, I imagine even forcing cubic to notice all of the 5x5 pixels would still be faster. Regards Craig de Stigter On Thu, Sep 30, 2010 at 10:34 AM, Even Rouault <even.roua...@mines-paris.org > wrote: > Craig, > > The main reason is that you are using gdalwarp to reduce an image by a > large > factor and not reproject it, which generally only involves image resizing > by > small factors. The implementation of the bilinear and cubic resampling > algorithms is currently not designed for the pure resizing use case and > takes > only into account a few source pixels (basically if to compute a > destination > pixel you would need to take into account a 5x5 source window, they will > only > used the 4 corners of that square, which fine usually since those are just > the > immediate neighbours of the source pixel), whereas cubicspline and lancsoz > take into account more pixels (all the pixels in the 5x5 square). > > Best regards, > > Even > > Le mercredi 29 septembre 2010 22:27:01, Craig de Stigter a écrit : > > Hi folks > > > > I filed this bug <http://trac.osgeo.org/gdal/ticket/3740> on gdal a few > > weeks back and haven't heard anything since. > > > > Would someone mind taking a look at it? > > > > Thanks > > Craig de Stigter > -- Koordinates Ltd PO Box 1604, Shortland St, Auckland, New Zealand Phone +64-9-966 0433 Fax +64-9-969 0045 Web http://www.koordinates.com
_______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
