Showing OpenStreetMap tile boundary using OpenLayers

Question

I have a local tile source of OSM tiles. I'd like to show the tile zoom, x, y on the tile so that I can optimize and create small offline groups of tile for specific areas (polygons).

I can get the tile boundary to show by setting a negative gutter, but I need the tile url info (zoom, x, y) to help with the manual optimization.

I saw an online resource a while back that showed this exact information on a map, but I've lost it.

Here is my layer

var newLayer = new OpenLayers.Layer.OSM("GC-h", "tiles/GC/composite_h/${z}/${x}/${y}.png", {numZoomLevels: 19, gutter: -1, isBaseLayer: false});
map.addLayer(newLayer);

Answer 1

After half an hour of searching I found a service which generates images with your custom size and text. You can use this, and put x/y/z as text: http://placehold.it/256x256&text=12/123/321

It may have limiting usage terms.