pygame-KidsCanCode系列jumpy-part9-使用spritesheet

做过前端的兄弟应该都知道css sprite(也称css精灵)，这是一种常用的减少http请求次数的优化手段。把很多小图拼成一张大图，只加载1次，然后用css定位到不区的区域，从而展示不同的图片。游戏中也是类似的道理，如下图：

每一个小图片，都有自己的x,y,width,height信息，通常会放在一个xml中，类似：

<TextureAtlas imagePath="sprites.png">
    <SubTexture name="bronze_1.png" x="707" y="296" width="84" height="84"/>
    <SubTexture name="bronze_2.png" x="826" y="206" width="66" height="84"/>
    <SubTexture name="bronze_3.png" x="899" y="116" width="50" height="84"/>
    <SubTexture name="bronze_4.png" x="670" y="406" width="14" height="84"/>
    <SubTexture name="bubble.png" x="0" y="1662" width="211" height="215"/>
    <SubTexture name="bunny1_hurt.png" x="382" y="946" width="150" height="174"/>
    <SubTexture name="bunny1_jump.png" x="382" y="763" width="150" height="181"/>
    <SubTexture name="bunny1_ready.png" x="614" y="1063" width="120" height="191"/>
    <SubTexture name="bunny1_stand.png" x="690" y="406" width="120" height="201"/>
    <SubTexture name="bunny1_walk1.png" x="678" y="860" width="120" height="201"/>
    <SubTexture name="bunny1_walk2.png" x="692" y="1458" width="120" height="207"/>
    <SubTexture name="bunny2_hurt.png" x="411" y="1866" width="150" height="174"/>
    <SubTexture name="bunny2_jump.png" x="416" y="1660" width="150" height="181"/>
    <SubTexture name="bunny2_ready.png" x="581" y="1265" width="121" height="191"/>
    <SubTexture name="bunny2_stand.png" x="584" y="0" width="121" height="201"/>
    <SubTexture name="bunny2_walk1.png" x="584" y="203" width="121" height="201"/>
    <SubTexture name="bunny2_walk2.png" x="678" y="651" width="121" height="207"/>
    <SubTexture name="cactus.png" x="707" y="134" width="117" height="160"/>
    <SubTexture name="carrot.png" x="820" y="1733" width="78" height="70"/>
    <SubTexture name="carrot_gold.png" x="814" y="1661" width="78" height="70"/>
    <SubTexture name="carrots.png" x="812" y="554" width="54" height="49"/>
    <SubTexture name="cloud.png" x="0" y="1152" width="260" height="134"/>
    <SubTexture name="coin_bronze.png" x="329" y="1390" width="60" height="61"/>
    <SubTexture name="coin_gold.png" x="244" y="1981" width="61" height="61"/>
    <SubTexture name="coin_silver.png" x="307" y="1981" width="61" height="61"/>
    <SubTexture name="flame.png" x="900" y="1733" width="41" height="80"/>
    <SubTexture name="flyMan_fly.png" x="566" y="510" width="122" height="139"/>
    <SubTexture name="flyMan_jump.png" x="568" y="1534" width="122" height="135"/>
    <SubTexture name="flyMan_stand.png" x="568" y="1671" width="122" height="139"/>
    <SubTexture name="flyMan_still_fly.png" x="692" y="1667" width="120" height="132"/>
    <SubTexture name="flyMan_still_jump.png" x="698" y="1801" width="120" height="128"/>
    <SubTexture name="flyMan_still_stand.png" x="707" y="0" width="120" height="132"/>
    <SubTexture name="gold_1.png" x="698" y="1931" width="84" height="84"/>
    <SubTexture name="gold_2.png" x="829" y="0" width="66" height="84"/>
    <SubTexture name="gold_3.png" x="897" y="1574" width="50" height="84"/>
    <SubTexture name="gold_4.png" x="645" y="651" width="15" height="84"/>
    <SubTexture name="grass1.png" x="868" y="1877" width="58" height="57"/>
    <SubTexture name="grass2.png" x="784" y="1931" width="82" height="70"/>
    <SubTexture name="grass_brown1.png" x="534" y="1063" width="58" height="57"/>
    <SubTexture name="grass_brown2.png" x="801" y="752" width="82" height="70"/>
    <SubTexture name="ground_cake.png" x="0" y="576" width="380" height="94"/>
    <SubTexture name="ground_cake_broken.png" x="0" y="0" width="380" height="94"/>
    <SubTexture name="ground_cake_small.png" x="218" y="1456" width="201" height="100"/>
    <SubTexture name="ground_cake_small_broken.png" x="262" y="1152" width="200" height="100"/>
    <SubTexture name="ground_grass.png" x="0" y="288" width="380" height="94"/>
    <SubTexture name="ground_grass_broken.png" x="0" y="384" width="380" height="94"/>
    <SubTexture name="ground_grass_small.png" x="213" y="1662" width="201" height="100"/>
    <SubTexture name="ground_grass_small_broken.png" x="382" y="204" width="200" height="100"/>
    <SubTexture name="ground_sand.png" x="0" y="672" width="380" height="94"/>
    <SubTexture name="ground_sand_broken.png" x="0" y="1056" width="380" height="94"/>
    <SubTexture name="ground_sand_small.png" x="208" y="1879" width="201" height="100"/>
    <SubTexture name="ground_sand_small_broken.png" x="382" y="102" width="200" height="100"/>
    <SubTexture name="ground_snow.png" x="0" y="768" width="380" height="94"/>
    <SubTexture name="ground_snow_broken.png" x="0" y="480" width="380" height="94"/>
    <SubTexture name="ground_snow_small.png" x="213" y="1764" width="201" height="100"/>
    <SubTexture name="ground_snow_small_broken.png" x="382" y="306" width="200" height="100"/>
    <SubTexture name="ground_stone.png" x="0" y="96" width="380" height="94"/>
    <SubTexture name="ground_stone_broken.png" x="0" y="192" width="380" height="94"/>
    <SubTexture name="ground_stone_small.png" x="382" y="408" width="200" height="100"/>
    <SubTexture name="ground_stone_small_broken.png" x="232" y="1288" width="200" height="100"/>
    <SubTexture name="ground_wood.png" x="0" y="960" width="380" height="94"/>
    <SubTexture name="ground_wood_broken.png" x="0" y="864" width="380" height="94"/>
    <SubTexture name="ground_wood_small.png" x="218" y="1558" width="200" height="100"/>
    <SubTexture name="ground_wood_small_broken.png" x="382" y="0" width="200" height="100"/>
    <SubTexture name="jetpack.png" x="563" y="1843" width="133" height="160"/>
    <SubTexture name="jetpack_item.png" x="852" y="1089" width="65" height="77"/>
    <SubTexture name="lifes.png" x="868" y="1936" width="52" height="71"/>
    <SubTexture name="lighting_blue.png" x="895" y="453" width="55" height="114"/>
    <SubTexture name="lighting_yellow.png" x="897" y="0" width="55" height="114"/>
    <SubTexture name="mushroom_brown.png" x="814" y="1574" width="81" height="85"/>
    <SubTexture name="mushroom_red.png" x="812" y="453" width="81" height="99"/>
    <SubTexture name="particle_beige.png" x="563" y="2005" width="58" height="41"/>
    <SubTexture name="particle_blue.png" x="852" y="1168" width="51" height="49"/>
    <SubTexture name="particle_brown.png" x="820" y="1877" width="44" height="48"/>
    <SubTexture name="particle_darkBrown.png" x="784" y="2003" width="54" height="43"/>
    <SubTexture name="particle_darkGrey.png" x="826" y="1364" width="51" height="43"/>
    <SubTexture name="particle_green.png" x="800" y="1003" width="48" height="46"/>
    <SubTexture name="particle_grey.png" x="623" y="2005" width="38" height="41"/>
    <SubTexture name="particle_pink.png" x="829" y="86" width="53" height="46"/>
    <SubTexture name="portal_orange.png" x="0" y="1288" width="230" height="82"/>
    <SubTexture name="portal_orangeParticle.png" x="262" y="1254" width="20" height="20"/>
    <SubTexture name="portal_yellow.png" x="0" y="1372" width="230" height="82"/>
    <SubTexture name="portal_yellowParticle.png" x="284" y="1254" width="20" height="20"/>
    <SubTexture name="powerup_bubble.png" x="826" y="134" width="71" height="70"/>
    <SubTexture name="powerup_bunny.png" x="826" y="1220" width="71" height="70"/>
    <SubTexture name="powerup_empty.png" x="894" y="1661" width="71" height="70"/>
    <SubTexture name="powerup_jetpack.png" x="820" y="1805" width="71" height="70"/>
    <SubTexture name="powerup_wings.png" x="826" y="1292" width="71" height="70"/>
    <SubTexture name="silver_1.png" x="584" y="406" width="84" height="84"/>
    <SubTexture name="silver_2.png" x="852" y="1003" width="66" height="84"/>
    <SubTexture name="silver_3.png" x="899" y="1219" width="50" height="84"/>
    <SubTexture name="silver_4.png" x="662" y="651" width="14" height="84"/>
    <SubTexture name="smoke.png" x="879" y="1364" width="51" height="48"/>
    <SubTexture name="spikeBall1.png" x="534" y="763" width="142" height="148"/>
    <SubTexture name="spikeBall_2.png" x="464" y="1122" width="148" height="141"/>
    <SubTexture name="spikeMan_jump.png" x="736" y="1063" width="114" height="155"/>
    <SubTexture name="spikeMan_stand.png" x="814" y="1417" width="90" height="155"/>
    <SubTexture name="spikeMan_walk1.png" x="704" y="1256" width="120" height="159"/>
    <SubTexture name="spikeMan_walk2.png" x="812" y="296" width="90" height="155"/>
    <SubTexture name="spike_bottom.png" x="894" y="206" width="51" height="87"/>
    <SubTexture name="spike_top.png" x="885" y="752" width="51" height="87"/>
    <SubTexture name="spikes_bottom.png" x="147" y="1988" width="95" height="53"/>
    <SubTexture name="spikes_top.png" x="232" y="1390" width="95" height="53"/>
    <SubTexture name="spring.png" x="420" y="1558" width="145" height="77"/>
    <SubTexture name="springMan_hurt.png" x="800" y="860" width="110" height="141"/>
    <SubTexture name="springMan_stand.png" x="801" y="609" width="110" height="141"/>
    <SubTexture name="spring_in.png" x="0" y="1988" width="145" height="57"/>
    <SubTexture name="spring_out.png" x="434" y="1265" width="145" height="110"/>
    <SubTexture name="sun1.png" x="534" y="913" width="142" height="148"/>
    <SubTexture name="sun2.png" x="421" y="1390" width="148" height="142"/>
    <SubTexture name="wingMan1.png" x="382" y="635" width="174" height="126"/>
    <SubTexture name="wingMan2.png" x="0" y="1879" width="206" height="107"/>
    <SubTexture name="wingMan3.png" x="0" y="1559" width="216" height="101"/>
    <SubTexture name="wingMan4.png" x="0" y="1456" width="216" height="101"/>
    <SubTexture name="wingMan5.png" x="382" y="510" width="182" height="123"/>
    <SubTexture name="wing_left.png" x="558" y="651" width="85" height="74"/>
    <SubTexture name="wing_right.png" x="571" y="1458" width="85" height="74"/>
</TextureAtlas>

上面这张图+这份xml，在pygame中我们称为spritesheet，通过xml中的name，找到对应的坐标、尺寸信息，就能取出指定的小图片，先研究下如何用python解析xml:

from os import path
from xml.dom.minidom import parse

xml_file_path = path.join(path.dirname(__file__), "../img/spritesheet_jumper.xml")
print(xml_file_path)

dom_tree = parse(xml_file_path)
root_textures = dom_tree.documentElement
sub_textures = root_textures.getElementsByTagName("SubTexture")

for texture in sub_textures:
    print("name:", texture.getAttribute("name"), ",x:",
          texture.getAttribute("x"), ",y:", texture.getAttribute("y"),
          ",", texture.getAttribute("width"), ",height:", texture.getAttribute("height"))

注：相对目录结构，参考下图：

上面这几行代码，就能把xml解析出来，输出类似下面这样：

...
name: bronze_1.png ,x: 707 ,y: 296 , 84 ,height: 84
name: bronze_2.png ,x: 826 ,y: 206 , 66 ,height: 84
name: bronze_3.png ,x: 899 ,y: 116 , 50 ,height: 84
name: bronze_4.png ,x: 670 ,y: 406 , 14 ,height: 84
...

知道了xml如何解析，下面就是如何取出指定小图片，借助pygame的最小框架，做一个测试：

import pygame
from os import path
from xml.dom.minidom import parse

# 游戏中的一些常量定义
SIZE = (WIDTH, HEIGHT) = (380, 380)
FPS = 10

# 颜色常量定义
BLACK = 0, 0, 0
WHITE = 255, 255, 255

# 初始化
pygame.init()
pygame.mixer.init()

# 窗口、标题等初始化
screen = pygame.display.set_mode(SIZE)
pygame.display.set_caption("My Game")
clock = pygame.time.Clock()

spritesheet_image_file_name = path.join(path.dirname(__file__), "../img/spritesheet_jumper.png")
spritesheet_xml_file_name = path.join(path.dirname(__file__), "../img/spritesheet_jumper.xml")
spritesheet_image = pygame.image.load(spritesheet_image_file_name)
spritesheet_image.set_colorkey(BLACK)
spritesheet_dom_tree = parse(spritesheet_xml_file_name)
root_textures = spritesheet_dom_tree.documentElement
sub_textures = root_textures.getElementsByTagName("SubTexture")
dic_image = {}


# 解析xml，找出指定图片的坐标、尺寸信息
def get_image_rect(img_name):
    if dic_image.get(img_name):
        return dic_image[img_name]
    for texture in sub_textures:
        name = texture.getAttribute("name")
        if img_name == name:
            dic_image[img_name] = pygame.Rect(
                int(texture.getAttribute("x")),
                int(texture.getAttribute("y")),
                int(texture.getAttribute("width")),
                int(texture.getAttribute("height"))
            )
            return dic_image[img_name]


# 获取指定图片的Surface对象，同时支持旋转+缩放
def get_image(img_name, angle=0, scale=1.0):
    rect = get_image_rect(img_name);
    image = pygame.Surface((rect.width, rect.height))
    image.blit(spritesheet_image, (0, 0), rect)
    image.set_colorkey(BLACK)
    new_image = pygame.transform.rotozoom(image, angle, scale)
    new_image.set_colorkey(BLACK)
    return new_image


# 循环入口
running = True
while running:

    # 设置帧数
    clock.tick(FPS)

    # 事件处理
    for event in pygame.event.get():
        # 退出处理
        if event.type == pygame.QUIT:
            running = False

    # (update) 游戏更新逻辑(比如：改动角色的位置或一些重要变量等，这里仅演示更新当前时间)
    image1 = get_image("bunny1_hurt.png", 0, 0.5)
    image2 = get_image("bunny1_walk1.png", 45, 0.5)
    image3 = get_image("bunny2_stand.png", -45, 0.5)

    # (draw)渲染屏幕
    screen.fill(BLACK)  # 先准备一块黑布
    screen.blit(image1, (0, 0), image1.get_rect())
    screen.blit(image2, (200, 200), image2.get_rect())
    screen.blit(image3, (200, 50), image3.get_rect())

    # 屏幕内容刷新
    pygame.display.update()

# 循环结束后，退出游戏
pygame.quit()

运行效果如下：

好了，前戏足够了，回到jumpy的游戏中来，在sprites.py中，新建一个类：

class Spritesheet:
    def __init__(self, png_file_name, xml_file_name):
        self.sprite_sheet = pg.image.load(png_file_name)
        self.sprite_sheet_dom_tree = parse(xml_file_name)
        self.dic_image = {}
        self.root_textures = self.sprite_sheet_dom_tree.documentElement
        self.sub_textures = self.root_textures.getElementsByTagName("SubTexture")

    def get_image_rect(self, img_name):
        if self.dic_image.get(img_name):
            return self.dic_image[img_name]
        for texture in self.sub_textures:
            name = texture.getAttribute("name")
            if img_name == name:
                self.dic_image[img_name] = pg.Rect(
                    int(texture.getAttribute("x")),
                    int(texture.getAttribute("y")),
                    int(texture.getAttribute("width")),
                    int(texture.getAttribute("height"))
                )
                return self.dic_image[img_name]

    def get_image(self, img_name):
        rect = self.get_image_rect(img_name)
        image = pg.Surface((rect.width, rect.height))
        image.blit(self.sprite_sheet, (0, 0), rect)
        image = pg.transform.scale(image, (rect.width // 3, rect.height // 3))
        image.set_colorkey(BLACK, 1)
        return image

同时原有的Player.py类，初始化时,image换成加载图片(终于可以换掉单调的小方块了）

class Player(pg.sprite.Sprite):
    def __init__(self, game):
        ...
        self.image = self.game.spritesheet.get_image("bunny1_stand.png")
        self.rect = self.image.get_rect()
        ...

最后看看main.py这个主类，还记得上一回，为了加载历史最高得分，新增了一个load_data函数吗？现在又用到了它了：

    def load_data(self):
        # 加载历史最高分
        ...
        # load spritesheet
        self.spritesheet = Spritesheet(path.join(self.dir, "../img/spritesheet_jumper.png"),
                                       path.join(self.dir, "../img/spritesheet_jumper.xml"))

源码：https://github.com/yjmyzz/kids-can-code/tree/master/part_09