[MapProxy] Merging two transparent layers

[Tobias Lohner]

Hello,

i'm trying to merge two transparent layers with MapProxy into one 
(/service?layers=layer1,layer2&transparent=true), but somehow the lower 
of the two layers get's very transparent.

Both layers are PNGA, the output format is PNGA, too.

My mapproxy.yaml looks like this (the second layer's configuration is 
identical):

--- snip ---
services:
   wms:
     srs: ['EPSG:3857']
     image_formats: ['image/png']

layers:
   - name: layer1
     title: Layer1 WMS
     sources: [layer1_cache]

caches:
   layer1_cache:
     grids: [GLOBAL_MERCATOR]
     sources: [layer1_mapserver]

sources:
   layer1_mapserver:
     type: mapserver
     supported_srs: ['EPSG:3857']
     req:
       layers: layer1
       transparent: true
     [...]

globals:
   image:
     paletted: false
--- snap ---

If I call the wms with transparent=false the lower layer get's a white 
background but everything looks ok (except the missing transparency).

These are my generated images:
http://lohner-net.de/skylines/layer1.png (only layer1)
http://lohner-net.de/skylines/layer2.png (only layer2)
http://lohner-net.de/skylines/merged_layers.png (layer1,layer2)
http://lohner-net.de/skylines/merged_layers_opaque.png (layer1,layer2 
with transparent=false)

I've tried that with MapProxy 1.5 and 1.6a.

Any ideas?


Tobias

-- 
Nichts gibt ein größerer Vergügen als den Betrüger zu betrügen.
		-- Karl Wilhelm Ramler