[MapProxy] How do I get these tile sets overlayed with transparency?

[Michael Heerdegen]

Daniel Cebulla via MapProxy <mapproxy at lists.osgeo.org> writes:

> Hi Michael,

Hi Daniel!

> [...] I think you have to sett "paletted" to "false" to get this work.

Thank you very much.

Unfortunately it doesn't make a difference.


> I am using transparent caches and I have set this option to false, so
> I think this should solve the issue.

Are you able to share an example?  You can send it to me privately.


Anyway, it seems that transparency is a bigger issue, there are several
related "doesn't work at all" kind bugs:

  https://github.com/mapproxy/mapproxy/issues?q=is%3Aissue+is%3Aopen+transparency

and it also seems that the behavior at least sometimes and partially
depends on the environment (installed image processing libraries, python
stuff, whatever).


Whatever I tried to affect the image format, the cached tiles are always
reported as 8 bit by the "file" command.  Didn't investigate much
further here.  Dunno if the "file" output is reliable.  Gimp didn't
dissent for the tiles I tried, though.

In theory, mapproxy should be able to interpret (near) white as
transparent, independent from alpha channels, AFAIU.  But this also
doesn't work reliably (see the bug reports).

Also note that I can advice my cache with disable_storage: true - or
disable caching entirely, building the layer directly from the sources.
The visual result is always exactly the same, unexpected one.  The
problem is not cache related.

The only real transparency I have ever seen is the example in this
report:

  https://github.com/mapproxy/mapproxy/issues/952

where already the source contains multiple layers.

If anyone could contribute a working example involving transparency, I
would maybe be able to find out what makes a difference and find a
workaround for my use case.


Thank you,

Michael.