Use pixels from upper zoom levels

[IvanSanchez]

When shifting a canvas around, it gets clear pixels.

There should be a way to keep canvases from upper levels, and copy the corresponding pixels from there. That should get rid of multiple transparent canvases when some overlapping tiles are being loaded/pruned.

[ebrensi]

Not sure what this means. But I would be down to try if you explain it. I am already using this plugin in my app.

[IvanSanchez]

It means that this piece of code....

Leaflet.TileLayer.NoGap/L.TileLayer.NoGap.js

Lines 30 to 34 in ab4f107

	level.canvas = L.DomUtil.create(
	"canvas",
	"leaflet-tile-container leaflet-zoom-animated",
	this._container
	);

...is creating an empty canvas.

Instead, it should iterate through this._levels, choose one of the existing upper levels, and perform a drawImage() call to copy pixels from an existing level canvas to the most recent level canvas.

Once that's working, implement removal of the pre-existing level (or make it invisible so it caches data??) and catch race conditions (e.g. tiles being loaded to a non-existing level should fail gracefully)