[MapProxy] Deliver Grayscale Images on the fly

[Johannes Weskamm]

Hi List,

Is there an option to deliver already cached, colored tiles through 
mapproxy so that the output becomes grayscale?
I would like to have my colored map accessible through 2 layers, one in 
color and one in grayscale.
I think its most efficient to use the colored cache and transform the 
images on the fly to grayscale. So we can avoid a second cache with 
"duplicate" information.

If there is no option, i could contribute a patch for this.

Greets,

Johannes Weskamm