Concretely, % 1:% 2,% 3,% 4,% 5,% 6,% 7,% 8,% 9,% 10,% 11,% 12,% 13,% 14,% 15,% 16,% 17,% 18,% 19,% 20,% 21,% 22,% 23,% 24,% 25,% 26,% 27,% 28,% 29,% 30,% 31,% 32,% 33,% 34,% 35,% 36,% 37,% 38,% 39,% 40,% 41,% 42,% 43,% 44,% 45,% 46,% 47,% 48,% 49,% 50,% 51,% 52,% 53,% 54,% 55,% 55,% 56,% 57,% 58,% 59,% 60,% 61,% 61,% 62,% 63,% 64,% 65,% 66,% 68,% 69,% 70,% 71,% 72,% 70,% 72,% 73,% 75,% 79,% 70,% 72,% 75,% 79,%. You choose the axis — horizontal produces a mirror image, vertical produces an upside-down reflection — and the whole file is transformed on it.