[gdal-dev] gdal2tiles.py of transparent background vrt/png gives black background tiles

Grégory Bataille gregory.bataille at gmail.com
Mon Apr 24 21:45:15 PDT 2017

Hey John,

That's a lot of information to process :)
So your conclusion would be that gdal2tiles does not handle TIF "Byte"
files properly?

Would you be able to submit some samples of working TIF + VRT and
non-working ones so that I might have a look in the future if it's a bug?

Gregory Bataille

On Tue, Apr 25, 2017 at 3:41 AM, John W. Glendening <glendening at drjack.net>

> 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
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