如何使用 PyGame 淡出和返回屏幕? [英] How to fade the screen out and back in using PyGame?

问题描述

所以我试图在使用 PyGame 完成一个关卡后淡出并重新进入我的屏幕.我的问题是只有淡出()有效，而不是淡入().调用fadein() 时，屏幕变黑几秒钟，然后突然显示下一个级别.我找不到问题，有什么想法吗?

So I am trying to fade my screen out and back in after completing a level using PyGame. My problem is that only the fadeout() works and not the fadein(). When calling the fadein() the screen turns black for a few seconds then suddenly shows the next level. I can't find the problem, any ideas?

def fadeout():
    fadeout = pg.Surface((screen_width, screen_height))
    fadeout = fadeout.convert()
    fadeout.fill(black)
    for i in range(255):
        fadeout.set_alpha(i)
        screen.blit(fadeout, (0, 0))
        pg.display.update()


def fadein():
    fadein = pg.Surface((screen_width, screen_height))
    fadein = fadein.convert()
    fadein.fill(black)
    for i in range(255):
        fadein.set_alpha(255-i)
        screen.blit(fadein, (0, 0))
        pg.display.update()

推荐答案

你的问题是你淡入黑屏，所以你看不到任何效果.顶部绘制有黑色半透明 Surface 的黑色屏幕仍然是黑色的 Surface.

Your problem is that you fade in to a black screen, so you don't see any effect. A black screen with a black half-translucent Surface drawn on top is still a black Surface.

您应该渲染关卡的第一帧，并在将 fadein 表面块传输到屏幕上之前将该 Surface 块传输到屏幕上.

You should render the first frame of your level, and blit that Surface to the screen before blitting the fadein surface onto the screen.

这是我一起破解的一个简单示例.按一个键可以从一个场景切换到下一个场景.

Here's a simple example that I hacked together. Press a key to switch from one scene to the next.

import pygame
import random
from itertools import cycle

class Cloud(pygame.sprite.Sprite):
    def __init__(self, x, y):
        super().__init__()
        self.image = pygame.Surface((50, 20))
        self.image.set_colorkey((11, 12, 13))
        self.image.fill((11, 12, 13))
        pygame.draw.ellipse(self.image, pygame.Color('white'), self.image.get_rect())
        self.rect = self.image.get_rect(topleft=(x,y))

    def update(self, dt, events):
        self.rect.move_ip(dt/10, 0)
        if self.rect.left >= pygame.display.get_surface().get_rect().width:
            self.rect.right = 0

class DayScene:
    def __init__(self):
        self.clouds = pygame.sprite.Group(Cloud(0, 30), Cloud(100, 40), Cloud(400, 50))

    def draw(self, screen):
        screen.fill(pygame.Color('lightblue'))
        self.clouds.draw(screen)

    def update(self, dt, events):
        self.clouds.update(dt, events)

class NightScene:
    def __init__(self):
        sr = pygame.display.get_surface().get_rect()
        self.sky = pygame.Surface(sr.size)
        self.sky.fill((50,0,50))
        for x in random.sample(range(sr.width), 50):
            pygame.draw.circle(self.sky, (200, 200, 0), (x, random.randint(0, sr.height)), 1)
        self.clouds = pygame.sprite.Group(Cloud(70, 70), Cloud(60, 40), Cloud(0, 50), Cloud(140, 10), Cloud(100, 20))

    def draw(self, screen):
        screen.blit(self.sky, (0, 0))
        self.clouds.draw(screen)

    def update(self, dt, events):
        self.clouds.update(dt, events)

class Fader:

    def __init__(self, scenes):
        self.scenes = cycle(scenes)
        self.scene = next(self.scenes)
        self.fading = None
        self.alpha = 0
        sr = pygame.display.get_surface().get_rect()
        self.veil = pygame.Surface(sr.size)
        self.veil.fill((0, 0, 0))

    def next(self):
        if not self.fading:
            self.fading = 'OUT'
            self.alpha = 0

    def draw(self, screen):
        self.scene.draw(screen)
        if self.fading:
            self.veil.set_alpha(self.alpha)
            screen.blit(self.veil, (0, 0))

    def update(self, dt, events):
        self.scene.update(dt, events)

        if self.fading == 'OUT':
            self.alpha += 8
            if self.alpha >= 255:
                self.fading = 'IN'
                self.scene = next(self.scenes)
        else:
            self.alpha -= 8
            if self.alpha <= 0:
                self.fading = None

def main():
    screen_width, screen_height = 300, 300
    screen = pygame.display.set_mode((screen_width, screen_height))
    clock = pygame.time.Clock()
    dt = 0
    fader = Fader([DayScene(), NightScene()])

    while True:
        events = pygame.event.get()
        for e in events:
            if e.type == pygame.QUIT:
                return
            if e.type == pygame.KEYDOWN:
                fader.next()

        fader.draw(screen)
        fader.update(dt, events)

        pygame.display.flip()
        dt = clock.tick(30)

main()

通过将每个场景抽象到它自己的类并将场景更改委托给 Fader 类，我们能够让场景继续(或添加一个简单的 if声明以防止这种情况)并在淡入淡出时处理事件.

By abstracting each scene into it's own class and delegating the scene change to the Fader class, we're able to let the scenes continue (or add a simple if statement to prevent that) and to handle events while fading.

这篇关于如何使用 PyGame 淡出和返回屏幕?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！