title: How to use a unique PNG for multiple tile?
body: <p>I want to use an offline map with Leaflet so I use PNG for my tiles.
  I want to use a unique image for the water so I don't need to have a lot of identical PNG.</p>
  
  <p>The files are stored this way 
  myMap/z/x/y.png
  With z the level of zoom, x and y the coordinate.</p>
  
  <p>I think I can easily get the z, x and y of all the water tiles.
  I just need to know if it's possible to tell Leaflet that if a tile with the same z, x and y than one in the array (or map or something else), it display myMap/water.png instead.</p>