Am 26.09.2014 um 19:22 schrieb Even Rouault <even.roua...@spatialys.com>:
> Peter, > Hi Even, > This is an interesting proof of concept. > > I have several notes : > - not sure about your naming conventions. For me your 'top' and 'bottom' must > be inverted. In imaging convention, the y of top is < to the y of bottom > - the formula is only appropriate for a resampling up to a factor of 2 > - you might have edge effects at block border since you clamp to the current > block. For example, this could be problematic when operating on blocks with a > 1-line height. > - something ready for upstreaming would probably involve adding a new > argument > to RasterIO to specify the resampling method, and as you noted, generalizing > to other data types. > - taking into nodata, alpha channel, etc.. would be necessary > > Would probably be interesting to think if we cannot share code with overview > computation. But not immediately trivial to do so. > I agree with all of the above points. Most choices were made to keep the change simple. > Best regards, > > Even > Regards, Peter >> >> I finally took the time to have a better look at this. >> >> The attached patch is only for our special case, where data arrives in 8 >> bit bands and is certainly far from being decent (I've written my last >> C++ code approx. 15 years ago). Anyway, the image quality seems indeed >> to improve sensibly. >> >> I used the current SVN version as a base for the development. >> >> Applying the patch I get from >> https://dl.dropboxusercontent.com/u/4935329/resampling_tests/basemap.2000x2 >> 000-quasiorig.jpg to this >> https://dl.dropboxusercontent.com/u/4935329/resampling_tests/basemap.2000x2 >> 000.bilinear.jpg . >> >> Anyway, the execution time approximatly doubles (on my 2011 notebook it >> passes from ~ 1.8 s to ~ 3.4 s), which in our case is not really an >> issue, but probaly for almost everybody else. >> >> The command line is, starting from the compilation dir: >> >> apps/gdal_translate -srcwin 35555000 23538000 2500 2500 -of JPEG >> -outsize 2000 2000 basemap.xml basemap.2000x2000.bilinear.jpg . >> >> Any comment is highly appreciated. >> >> Regards and a nice weekend, >> >> Peter > > -- > Spatialys - Geospatial professional services > http://www.spatialys.com _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
