Finally having some success using ImageMagick convert, I backed up by not using its -Truecolor flag, i.e. using only a -depth 8 flag, which produced a 4 band RGBA. Creating a .vrt and running gdal2tiles.py produced successful results, _without_ needing the -a 0,0,0,0 argument. I then pushed things further by adding the partial opacity polygons back in. That did produce partial opacity polygons in the tiles, but instead of being magenta they were gray. Don't know how to explain that, probably a limitation in gdal2tiles.py - but it is at least partial success.
Summary: IM convert produced a "UInt16" format TIF when lines are drawn on its blank transparent canvas, whereas drawing them on a pre-created background map image produced "Byte" format TIFs. The gdalbuildvrt understood that and so indicated in the .vrt file it produced. But gdal2tiles.py apparently only understands "Byte" format files. The IM convert requires a "-depth 8" flag to produce such files. John Glendening -- John W. (Jack) Glendening 831-484-6929 25953 Deer Run Lane Salinas, CA 93908 _______________________________________________ gdal-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/gdal-dev
