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新年伊始患民，各位同學(xué)又給今年定下了什么小目標(biāo)呢羔挡？

本篇文章签财，我們帶給大家一個(gè)小案例：用 Python 制作一個(gè)炫酷煙花秀敬鬓，祝大家新年快樂(lè)淹朋，順便也提前送上春節(jié)祝福笙各。

開(kāi)始之前先看一下最終效果：

環(huán)境介紹：

語(yǔ)言：Python

庫(kù)：Pygame

原理介紹

在介紹代碼之前，先介紹下 Pygame 繪制煙花的基本原理础芍，煙花從發(fā)射到綻放一共分為三個(gè)階段：

1杈抢，發(fā)射階段：在這一階段煙花的形狀是線性向上，通過(guò)設(shè)定一組大小不同仑性、顏色不同的點(diǎn)來(lái)模擬“向上發(fā)射” 的運(yùn)動(dòng)運(yùn)動(dòng)春感，運(yùn)動(dòng)過(guò)程中 5個(gè)點(diǎn)被賦予不同大小的加速度，隨著時(shí)間推移虏缸，后面的點(diǎn)會(huì)趕上前面的點(diǎn)鲫懒，最終所有點(diǎn)會(huì)匯聚在一起，處于 綻放準(zhǔn)備階段刽辙；

2窥岩，煙花綻放：煙花綻放這個(gè)階段，是由一個(gè)點(diǎn)分散多個(gè)點(diǎn)向不同方向發(fā)散宰缤，并且每個(gè)點(diǎn)的移動(dòng)軌跡可需要被記錄颂翼，目的是為了追蹤整個(gè)綻放軌跡。

3慨灭，煙花凋零朦乏，此階段負(fù)責(zé)描繪綻放后煙花的效果，綻放后的煙花氧骤，而在每一時(shí)刻點(diǎn)的下降速度和亮度（代碼中也叫透明度）是不一樣的呻疹，因此在代碼里，將煙花綻放后將每個(gè)點(diǎn)賦予兩個(gè)屬性：分別為重力向量和生命周期筹陵，來(lái)模擬煙花在不同時(shí)期時(shí)不同的展現(xiàn)效果刽锤，

代碼實(shí)操

代碼部分將煙花封裝為三個(gè)類：

Firework : 煙花整體；

Particle：煙花粒子（包含軌跡）

Trail：煙花軌跡朦佩，本質(zhì)上是一個(gè)點(diǎn) 并思。

三個(gè)類之間的關(guān)系為：一個(gè)Firework 由多個(gè) Particle 構(gòu)成，而一個(gè) Particle 由多個(gè) Trail 構(gòu)成

首先設(shè)置全局變量语稠，例如重力向量宋彼，窗口大小，Trail 的顏色列表（多為灰色或白色）以及不同狀態(tài)下 Trail 之間間隔

gravity = vector(0, 0.3)
DISPLAY_WIDTH = DISPLAY_HEIGHT = 800


trail_colours = [(45, 45, 45), (60, 60, 60), (75, 75, 75), (125, 125, 125), (150, 150, 150)]
dynamic_offset = 1
static_offset = 3

創(chuàng)建 Trail 類仙畦，定義 show 方法繪制軌跡 输涕、get_pos 實(shí)時(shí)獲取軌跡坐標(biāo)

class Trail:

    def __init__(self, n, size, dynamic):
        self.pos_in_line = n
        self.pos = vector(-10, -10)
        self.dynamic = dynamic

        if self.dynamic:
            self.colour = trail_colours[n]
            self.size = int(size - n / 2)
        else:
            self.colour = (255, 255, 200)
            self.size = size - 2
            if self.size < 0:
                self.size = 0

    def get_pos(self, x, y):
        self.pos = vector(x, y)

    def show(self, win):
        pygame.draw.circle(win, self.colour, (int(self.pos.x), int(self.pos.y)), self.size)

Particle 類核心代碼

class Particle:

    def __init__(self, x, y, firework, colour):
        self.firework = firework
        self.pos = vector(x, y)
        self.origin = vector(x, y)
        self.radius = 20
        self.remove = False
        self.explosion_radius = randint(5, 18)
        self.life = 0
        self.acc = vector(0, 0)
        # trail variables
        self.trails = []  # stores the particles trail objects
        self.prev_posx = [-10] * 10  # stores the 10 last positions
        self.prev_posy = [-10] * 10  # stores the 10 last positions

        if self.firework:
            self.vel = vector(0, -randint(17, 20))
            self.size = 5
            self.colour = colour
            for i in range(5):
                self.trails.append(Trail(i, self.size, True))
        else:
            self.vel = vector(uniform(-1, 1), uniform(-1, 1))
            self.vel.x *= randint(7, self.explosion_radius + 2)
            self.vel.y *= randint(7, self.explosion_radius + 2)
            # 向量
            self.size = randint(2, 4)
            self.colour = choice(colour)
            # 5 個(gè) tails總計(jì)
            for i in range(5):
                self.trails.append(Trail(i, self.size, False))

    def apply_force(self, force):
        self.acc += force

    def move(self):
        if not self.firework:
            self.vel.x *= 0.8
            self.vel.y *= 0.8
        self.vel += self.acc
        self.pos += self.vel
        self.acc *= 0

        if self.life == 0 and not self.firework:  # check if particle is outside explosion radius
            distance = math.sqrt((self.pos.x - self.origin.x) ** 2 + (self.pos.y - self.origin.y) ** 2)
            if distance > self.explosion_radius:
                self.remove = True

        self.decay()

        self.trail_update()

        self.life += 1

    def show(self, win):
        pygame.draw.circle(win, (self.colour[0], self.colour[1], self.colour[2], 0), (int(self.pos.x), int(self.pos.y)),
                           self.size)

    def decay(self):  # random decay of the particles
        if 50 > self.life > 10:  # early stage their is a small chance of decay
            ran = randint(0, 30)
            if ran == 0:
                self.remove = True
        elif self.life > 50:
            ran = randint(0, 5)
            if ran == 0:
                self.remove = True

Firework 類核心代碼

class Firework:
    def __init__(self):
        # 隨機(jī)顏色
        self.colour = (randint(0, 255), randint(0, 255), randint(0, 255))
        self.colours = (
            (randint(0, 255), randint(0, 255), randint(0, 255)),
            (randint(0, 255), randint(0, 255), randint(0, 255)),
            (randint(0, 255), randint(0, 255), randint(0, 255)))
        self.firework = Particle(randint(0, DISPLAY_WIDTH), DISPLAY_HEIGHT, True,
                                 self.colour)  # Creates the firework particle
        self.exploded = False
        self.particles = []
        self.min_max_particles = vector(100, 225)

    def update(self, win):  # called every frame
        if not self.exploded:
            self.firework.apply_force(gravity)
            self.firework.move()
            for tf in self.firework.trails:
                tf.show(win)

            self.show(win)

            if self.firework.vel.y >= 0:
                self.exploded = True
                self.explode()
        else:
            for particle in self.particles:
                particle.apply_force(vector(gravity.x + uniform(-1, 1) / 20, gravity.y / 2 + (randint(1, 8) / 100)))
                particle.move()
                for t in particle.trails:
                    t.show(win)
                particle.show(win)

 
    def remove(self):
        if self.exploded:
            for p in self.particles:
                if p.remove is True:
                    self.particles.remove(p)

            if len(self.particles) == 0:
                return True
            else:
                return False

最后，寫(xiě)一個(gè) main 方法來(lái)對(duì) pygame 環(huán)境進(jìn)行初始化议泵，例如背景圖片占贫，文字，設(shè)置頁(yè)面刷新間隔先口，程序中設(shè)置的每 60ms 刷新一次型奥。

pygame.display.set_caption("Fireworks in Pygame") # 標(biāo)題
    background = pygame.image.load("img/1.png") # 背景
    myfont = pygame.font.Font("img/simkai.ttf",80)
    myfont1 = pygame.font.Font("img/simkai.ttf", 30)

    testsurface = myfont.render("元旦快樂(lè)",False,(255,255,255))
    testsurface1 = myfont1.render("By:小張Python", False, (255, 255, 255))

    # pygame.image.load("")
    win = pygame.display.set_mode((DISPLAY_WIDTH, DISPLAY_HEIGHT))
    # win.blit(background)
    clock = pygame.time.Clock()

    fireworks = [Firework() for i in range(2)]  # create the first fireworks
    running = True

    while running:
        clock.tick(60)
        win.fill((20, 20, 30))  # draw background
        win.blit(background,(0,0))
        win.blit(testsurface,(200,200))
        win.blit(testsurface1, (300,200))

        if randint(0, 20) == 1:  # create new firework
            fireworks.append(Firework())

        update(win, fireworks)

另外程序中會(huì)對(duì)你的按鍵命令進(jìn)行監(jiān)控：

• 當(dāng)按下鍵 1時(shí) 瞳收，會(huì)立即生成一個(gè)新的 “煙花”；
• 當(dāng)按下鍵 2時(shí)厢汹，會(huì)同時(shí)生成 10 個(gè) “煙花”

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False
            if event.type == pygame.KEYDOWN:  # Change game speed with number keys
                if event.key == pygame.K_1: # 按下 1
                    fireworks.append(Firework())
                if event.key == pygame.K_2: # 按下 2 加入10個(gè)煙花
                    for i in range(10):
                        fireworks.append(Firework())

小結(jié)

總的來(lái)說(shuō)螟深，整個(gè)小案例的代碼量不算很多，一共250行左右烫葬，但案例中涉及到較為復(fù)雜的繪制邏輯和抽象的類之間的封裝關(guān)系界弧，因此大家理解代碼相對(duì)會(huì)需要耗費(fèi)點(diǎn)時(shí)間。

本篇文章主要介紹了如何用 Pygame 來(lái)模擬一個(gè)煙花綻放過(guò)程搭综，核心內(nèi)容大致兩點(diǎn)：第一垢箕，如何用繪制點(diǎn)的方式來(lái)模擬煙花綻放運(yùn)動(dòng)軌跡；第二兑巾，介紹Pygame 一些基礎(chǔ)用法：替換背景条获，繪制文字，更新?tīng)顟B(tài)等功能蒋歌。