用Python的Turtle模塊繪製五星紅旗

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用Python的Turtle模塊繪製五星紅旗

在Udacity上課時學到了python的turtle方法，這是一個很經典的用來教小孩兒編程的圖形模塊，最早起源於logo語言。python本身內置了這個模塊，其可視化的方法可以幫助小孩兒對編程的一些基本理念有所理解。
在作業提交的論壇裏看到很多turtle畫出來的精美圖形，想不出什麼要畫的東西，於是決定拿五星紅旗來練練手。

前期準備

• 五星紅旗繪製參數
• Turtle官方文檔

turtle的基本操作

# 初始化屏幕
window = turtle.Screen()
# 新建turtle對象實例
import turtle
aTurtle = turtle.Turtle()
# 海龜設置
aTurtle.hideturtle()    # 隱藏箭頭
aTurtle.speed(10)       # 設置速度
# 前進後退，左轉右轉
aTurtle.fd(100)     # 前進100像素
aTurtle.right(90)   # 右轉90°
aTurtle.back(100)
aTurtle.left(90)
# 填充顏色
aTurtle.begin_fill()
aTurtle.fillcolor('yellow')
DoSomethinghere()
aTurtle.end_fill()
# 擡起筆和放下筆，這樣進行的操作不會留下痕跡
aTurtle.penup()
aTurtle.goto(start_pos)
aTurtle.fd(radius)
aTurtle.pendown()

繪製五星紅旗代碼

github地址：https://gist.github.com/dc11287081ee67075da8

#!/usr/bin/env python     
# -*- coding: utf-8 –*-
''' 對於turtle類的一些封裝方法，包括畫正多邊形，正多角形和五星紅旗。'''
__author__ = 'Hu Wenchao'

import turtle
import math

def draw_polygon(aTurtle, size=50, n=3):
    ''' 繪製正多邊形

    args:
        aTurtle: turtle對象實例
        size: int類型，正多邊形的邊長
        n: int類型，是幾邊形        
    '''
    for i in xrange(n):
        aTurtle.forward(size)
        aTurtle.left(360.0/n)

def draw_n_angle(aTurtle, size=50, num=5, color=None):
    ''' 繪製正n角形，默認爲黃色

    args:
        aTurtle: turtle對象實例
        size: int類型，正多角形的邊長
        n: int類型，是幾角形    
        color: str， 圖形顏色，默認不填色
    '''
    if color:
        aTurtle.begin_fill()
        aTurtle.fillcolor(color)
    for i in xrange(num):
        aTurtle.forward(size)
        aTurtle.left(360.0/num)
        aTurtle.forward(size)
        aTurtle.right(2*360.0/num)
    if color:
        aTurtle.end_fill()

def draw_5_angle(aTurtle=None, start_pos=(0,0), end_pos=(0,10), radius=100, color=None):
    ''' 根據起始位置、結束位置和外接圓半徑畫五角星

    args:
        aTurtle: turtle對象實例
        start_pos: int的二元tuple，要畫的五角星的外接圓圓心
        end_pos: int的二元tuple，圓心指向的位置座標點
        radius: 五角星外接圓半徑
        color: str， 圖形顏色，默認不填色    
    '''
    aTurtle = aTurtle or turtle.Turtle()
    size = radius * math.sin(math.pi/5)/math.sin(math.pi*2/5)
    aTurtle.left(math.degrees(math.atan2(end_pos[1]-start_pos[1], end_pos[0]-start_pos[0])))
    aTurtle.penup()
    aTurtle.goto(start_pos)
    aTurtle.fd(radius)
    aTurtle.pendown()
    aTurtle.right(math.degrees(math.pi*9/10))
    draw_n_angle(aTurtle, size, 5, color)

def draw_5_star_flag(times=20.0):
    ''' 繪製五星紅旗

    args:
        times: 五星紅旗的規格爲30*20， times爲倍數，默認大小爲10倍， 即300*200
    '''
    width, height = 30*times, 20*times
    # 初始化屏幕和海龜
    window = turtle.Screen()
    aTurtle = turtle.Turtle()
    aTurtle.hideturtle()
    aTurtle.speed(10)
    # 畫紅旗
    aTurtle.penup()
    aTurtle.goto(-width/2, height/2)
    aTurtle.pendown()
    aTurtle.begin_fill()
    aTurtle.fillcolor('red')
    aTurtle.fd(width)
    aTurtle.right(90)
    aTurtle.fd(height)
    aTurtle.right(90)
    aTurtle.fd(width)
    aTurtle.right(90)
    aTurtle.fd(height)
    aTurtle.right(90)    
    aTurtle.end_fill()
    # 畫大星星
    draw_5_angle(aTurtle, start_pos=(-10*times, 5*times), end_pos=(-10*times, 8*times), radius=3*times, color='yellow')  
    # 畫四個小星星
    stars_start_pos = [(-5, 8), (-3, 6), (-3, 3), (-5, 1)]
    for pos in stars_start_pos:
        draw_5_angle(aTurtle, start_pos=(pos[0]*times, pos[1]*times), end_pos=(-10*times, 5*times), radius=1*times, color='yellow')  
    # 點擊關閉窗口
    window.exitonclick()

if __name__ == '__main__':
        draw_5_star_flag()

效果圖