摘自：哈哈老师的日记

https://www.toutiao.com/a7051427670651077159

  哈哈老师设计的程序，学习实践一下。

一、三点画圆

  做一个圆形路径动画，给定起点和终点后，再自动计算一个运动幅度，使用复数求解函数，得到圆心坐标和半径值，然后就可以画出圆来。

二、动画

  在屏幕中间随便点一些点，依次得到坐标值，三个点画一个小球，使经过这三个点。
  在屏幕上随意点了5个点，生成了3个卫星。

运行效果

三、源程序

# circlepath.py

from base import *
  
W,H = 1280,800

def get_circle(p1,p2,p3):
    '''三点求圆，返回圆心和半径'''
    x, y, z = p1[0]+p1[1]*1j, p2[0]+p2[1]*1j, p3[0]+p3[1]*1j
    w = z-x
    w /= y-x
    c = (x-y)*(w-abs(w)**2)/2j/w.imag-x
    return (-c.real,-c.imag),abs(c+x)

class CirclePath:
    def __init__(self,center,r):
        self.center = Vector2(center)
        self.r = r
        self.angle = 0
        self.speed = 2

    def draw(self,canvas):
        self.angle += self.speed
        pos = self.center + Vector2(self.r,0).rotate(self.angle)
        pygame.draw.circle(canvas, (0,200,0),pos, 5)

points = []
circles = []
show_points = True  # 显示点

def setup():
    size(W,H)

def draw():
    global show_points
    for event in ctx.events:
        if event.type == pygame.KEYDOWN:
            if event.key == K_SPACE:
                show_points = not show_points
        if event.type == pygame.MOUSEBUTTONDOWN:
            points.append(event.pos)
            if len(points) >= 3:
                c,r = get_circle(points[-3],points[-2],points[-1])
                circles.append(CirclePath(c,r))

    ctx.screen.fill((0,0,0,100))
    if show_points:
        for p in points:
            pygame.draw.circle(ctx.screen, (100,100,0),p, 2)

    for circle in circles:
        circle.draw(ctx.screen)

run()

四、base.py

  base.py 是哈哈老师封装的 pygame ，主要是为了仿 processing 的调用方式。

# base.py

import pygame
from pygame.locals import *
from pygame.math import Vector2
import sys,random,math,os

width,height = 1920,1080
pygame.init()
window = None
pygame.display.set_caption('测试')

clock = pygame.time.Clock()
running = True

class real_contex():
    def __init__(self):
        self.screen = None
        x,y = pygame.mouse.get_pos()
        self.mouseX = x
        self.mouseY = y
        self.fps = 60

    def fill(self,color):
        self.window.fill(0)
        if self.screen is not None:
            self.screen.fill(color)

    def hsv_to_rgb(self,h,s,v,a=100):
        '''颜色转换'''
        c = pygame.Color(0,0,0,a)
        c.hsva = (h,s,v,a)
        return c

    def setup(self):
        pass

    def draw(self):
        pass

ctx = real_contex()

def size(w,h):
    global width,height,window
    width,height = w,h
    if w == 1920 and h == 1080:
        window = pygame.display.set_mode((width,height),FULLSCREEN)
    else:
        window = pygame.display.set_mode((width,height))

    ctx.window = window    
    # ctx.screen = window.convert_alpha() # 支持透明度
    ctx.screen = pygame.Surface((w,h), pygame.SRCALPHA)
    ctx.width = width
    ctx.height = height
    ctx.rect = window.get_rect()
    ctx.center = ctx.rect.center

def run():
    global running,window

    # 获取调用 run 函数的文件名
    m_name = sys._getframe(1).f_code.co_filename
    f_name = os.path.basename(m_name)
    module_name = os.path.splitext(f_name)[0]
    # print(f_name,module_name)
    # 通过文件名加载为模块，并动态获取 setup 和 draw 方法
    app_module = __import__(module_name)
    m_dir = dir(app_module)
    if 'setup' in m_dir:
        ctx.setup = app_module.setup
    if 'draw' in m_dir:
        ctx.draw = app_module.draw
    del m_dir

    ctx.setup()
    if window is None:
        size(800,600)
    while running:
        ctx.events = pygame.event.get()
        ctx.mouseX,ctx.mouseY = pygame.mouse.get_pos()
        for evt in ctx.events:
            if evt.type == QUIT:
                pygame.quit()
                sys.exit()
            if evt.type == KEYDOWN:
                if evt.key == K_ESCAPE:
                    pygame.quit()
                    sys.exit()

        ctx.draw()
        window.blit(ctx.screen,(0,0))
        pygame.display.update()
        clock.tick(ctx.fps)