tile_get_count();
Returns: Real
With this function you can get the total number of tiles, from
all layers, in a room.
var num = tile_get_count();
for (var i = 0; i < num; i++;)
{
tile_set_blend(tile_get_id(i), c_red);
}
The above code will get the total number of tiles in a room, then loop through them one at a time and set their blend colour to red.