Worldmap loads colour map before greyscale

General
1

In my Worldmap instance, I've got "OpenStreetMap Greyscale" and "ESRI Dark Grey" in the map list, and the first of these is my base map.

I don't know if it's a quirk of Leaflet or something to do with Worldmap itself, but I've noticed that when it loads map tiles, it always seems to load OpenStreetMap ones (NB: that's "OpenStreetMap", NOT "OpenStreetMap Greyscale") first and then the "OpenStreetMap Greyscale" ones over the top of them, even though "OpenStreetMap" isn't even selected in my map list. It's quite distracting, especially over a slower connection when zooming or scrolling.

Anybody have any idea why it's doing this, please?

2

I'm not really sure - but it may be because the greyscale is actually just a filter applied to the colour one - ie it processes each tile to turn it back into greyscale - so on slower devices it has to load the tile first then process it, and this is visible. (I'm not 100% sure but ...)

3

Thanks @dceejay, I think you might be right, looking at the network activity. I'm not seeing any greyscale images loading at all, although rather bizarrely it does (on a different map that has both colour and greyscale enabled) reload some colour tiles when changing from colour map to greyscale map! It's a shame it doesn't convert them to greyscale and then display them, but at least it's minimising the time taken to display the tile this way.

4

it saves having two sets of tiles... and in theory can be applied to any WMS map source.

5

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