get_tile_size_at_zoom

Gets the apparent size of the map tiles at the given fractional zoom level.

As the map is zoomed in, a tile gets bigger and bigger until, at the next integer zoom level, it "splits" into four tiles at the next zoom level. Thus, the size increase follows an exponential curve, base 2.

Parameters:

this	a MapSource
zoom_level	a zoom level

Returns:

the tile's size (width and height) in pixels for this map source at this zoom level