title: "Python使用DDA算法和中点Bresenham算法画直线"
date: 2018-06-11T19:28:02+08:00
tags: ["图形学"]
categories: ["Python"]
先上效果图
代码
#!/usr/bin/env python
# coding=utf-8
from pylab import *
from matplotlib.ticker import MultipleLocator
import matplotlib.patches as patches
'''
1. 输入直线两端点 x0,y0 xn,yn
2. 计算初始值delta_x, delta_y,k=delta_y/delta_x,d=0, x=x0,y=y0
3. 绘制点x,y
4. d更新为d+k,若d>0.5,则x,y更新为x+1,y+1,d=d-1;否则x,y更新为x+1,y
5. 重复3,4直到直线画完
'''
def init(ax, width):
# 设置长宽
ax.axis([0, width, 0, width])
# 设置主刻度标签的位置,标签文本的格式
majorLocator = MultipleLocator(1)
minorLocator = MultipleLocator(0.5)
ax.xaxis.set_major_locator(majorLocator)
ax.yaxis.set_major_locator(majorLocator)
# ax.xaxis.set_minor_locator(minorLocator)
# ax.yaxis.set_minor_locator(minorLocator)
ax.grid(True) # x坐标轴的网格使用主刻度
def add_pixel(x, y, ax, c):
x = round(x)
y = round(y)
if c == 1:
ax.add_patch(patches.Rectangle((x - 0.5, y - 0.5), 1, 1, color='b'))
ax.plot(x, y, 'r.')
else:
ax.add_patch(patches.Rectangle((x - 0.5, y - 0.5), 1, 1))
ax.plot(x, y, 'y.')
if __name__ == '__main__':
# 将一行的字符串分割并转化为数字
x0, y0, x1, y1, width = map(int, input("输入直线的两点和画布的边长: ").split(' '))
if x0>x1:
x0,x1=x1,x0
y0,y1=y1,y0
ax = subplot(121, aspect='equal',
title='modified Bresenham') # 改进的bresenham
ax.plot([x0, x1], [y0, y1], '-k')
bx = subplot(122, aspect='equal', title='DDA') # DDA
bx.plot([x0, x1], [y0, y1], '-k')
# 图形初始化
init(ax, width)
init(bx, width)
delta_x = x1 - x0
delta_y = y1 - y0
d = 0
if delta_x == 0:
k = 999999999
else:
k = delta_y / delta_x
x = round(x0)
y = round(y0)
'''
DDA算法
'''
if k > -1 and k < 1:
# X 最大位移
while True:
if x > x1:
break
add_pixel(x, y, bx, 1)
x = x+1
y = y+k
elif k >= 1:
# Y 最大位移
while True:
if y > y1:
break
add_pixel(x, y, bx, 1)
y = y+1
x = x+1/k
else:
while True:
if y < y1:
break
add_pixel(x, y, bx, 1)
y = y-1
x = x-1/k
'''
k的范围
1. (0,1) x为最大位移，y正向增加
2. (1,+inf) y为最大位移，x正向增加
3. (0,-1) x为最大位移，y负向增加
4. (-1,-inf)y为最大位移，y减小。x正向增加
'''
x = x0
y = y0
if k > 1:
while True:
if y > y1:
break
add_pixel(x, y, ax, 0)
y = y + 1
d = d + 1 / k
if d > 0.5:
x = x + 1
d = d - 1
elif k > 0:
while True:
if x > x1:
break
add_pixel(x, y, ax, 0)
x = x + 1
d = d + k
if d > 0.5:
y = y + 1
d = d - 1
elif k > -1:
while True:
if x > x1:
break
add_pixel(x, y, ax, 0)
x = x + 1
d = d - k
if d > 0.5:
y = y - 1
d = d - 1
else:
while True:
if y < y1:
break
add_pixel(x, y, ax, 0)
y = y - 1
d = d - 1 / k
if d > 0.5:
x = x + 1
d = d - 1
show()