local from = { x = -10, y = -10 }
local to = { x = 0, y = 0 }
--// находим длину
local size = { x = math.abs(from.x - to.x), y = math.abs(from.y - to.y) }
--// находим центр
local center = { x = from.x + size.x / 2, y = from.y - size.y / 2}
print(center.x, center.y)