Le mardi 18 septembre 2012 05:15:03, Nik Sands a écrit : > I'm very new to GDAL so please be gentle. My searching has found many > references to this problem, but no complete solutions that are explained > clearly enough for me to work through.
The Warp API is powerful, and thus admitedly complex to master. > > I'm using the GDAL API to read in a source image (could be from a variety > of formats), warp it to Spherical Mercator, and then write out the > reprojected image as a GeoTIFF. I would like the parts of the warped TIFF > that are not included in the original image to be represented by fully > transparent pixels instead of the black pixels that are being generated. > > I've set "ALPHA" to "YES" in the warp options but this has not helped. > I've also tried adding an extra transparent band, but this made the entire > output image transparent. Strange, perhaps you should retry. To have a transparency band added in the output of the warping, you need to set the band number in the GDALCreate() call to 1 + GDALGetRasterCount(hSrcDS), and also set psWarpOptions->nDstAlphaBand = 1 + GDALGetRasterCount(hSrcDS) This should be equivalent to the -dstalpha option of gdalwarp. By the way, if I were you, I would try to find the gdalwarp command line that fits my need, and then study its code source to extract what is needed for your use case. _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
