[OSM-dev] Task for OpenLayers buffs: tile grid layer?

Frederik Ramm frederik at remote.org
Thu Apr 26 22:21:51 BST 2007


    I would love to have an extra layer for the slippy map that I can 
switch on to see a tile grid. Each of the tiles of that layer would look 
like this:

  _                    _
|                      |

|_ z=12 x=1234 y=2345 _|

and be transparent otherwise. If displayed "on top" of the base layer, 
this would make a nice debug view to find out which tiles you want to 
edit or re-render or whatever.

I can easily create the 4096x4096 level 12 tiles and put them in a 
directory structure as required for the "likeGoogle" layer - but I 
haven't managed to convince OpenLayers and/or Firefox to actually make 
this display right. I created transparent PNG files and made the new 
layer an overlay layer instead of a base layer, but the desired 
transparency eluded me - it always showed *just* my layer instead of my 
layer on top of the base layer.

Has anybody done something similar already?

(Another option would of course be to but code into OpenLayers that 
prints the tile index at the right places. Much simpler in theory, but a 
look at the Javascript turned me off... maybe something like that is 
already there and just needs to be enabled?)


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00.09' E008°23.33'

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