Belaid MOA wrote: > Thanks for the reply. I do not see how anti-aliasing techniques could be > used here.
anti-aliasing when warping rasters requires computing how much the pixels of the source and destination overlap each-other. > Does anyone else have simple answers to the two elementary questions? sure: > > > According to GDAL code, a pixel/line (i,j), more precisely its center > > > (i+0.5,j+0.5), of the first image is mapped to the pixel/line (p,q) > of the > > > second image, where p and q are doubles that usually have fraction > parts. > > > My questions are: what is the meaning for these fractions? the point in the middle of a pixel in the source raster represents a particular lat-long location -- p and q are the location in the second image for the same lat-long -- chances are slim that it's going to land exactly on a pixel boundary, hence the fraction. Just like the middle of the source pixel is i+0.5, j+0.5, the middle of a destination pixel would be p+0.5, q+0.5. > Is it possible to use these fractions to compute the overlap between > the pixels of the two images using GDAL? yup -- think about the above, and do a little arithmatic (which i s the arithmetic done in the anti-aliasing code. HTH, -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception chris.bar...@noaa.gov _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
