1. 直线(2,5)~(7,9)
中点画线算法
a = y0 – y1 = -4
b = x1 – x0 = 5
c = x0y1 - x1y0 = -17
F(x, y) = -4x + 5y – 8 = 0
2a = -8
2(a+b) = 2
迭代次数 n = 7 – 2 – 1 = 4
故为(3, 6) (4, 7) (5, 7) (6, 8)
Bresenham 画线算法
△x = 5 △y = 4
迭代次数 n = 7 – 2 – 1 = 4
e1 + 2△y - 2△x(y1 – y0) = 1 > 0
e2 + 2△y - 2△x(y2 – y1) = -1 < 0
e3 + 2△y - 2△x(y3 – y2) = 7 > 0
故为(3, 6) (4, 7) (5, 7) (6, 8)
2.写出下列二维图形变换的变换矩阵:
1)绕(2,4)点顺时针旋转 30 度;
2)以(3,6)点为对称中心的中心对称变换;
3)以 y=3x-4 为对称轴的轴对称变换;
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